Tectonic Plates: What I need to know


Reflection on the unit/ teaching strategies

In reflection of the unit I thought I would do a SWOT analysis – this could be elaborated on further once the unit has been taught

Strengths:

  • Unit written with the Productive Pedagogies in mind – as described by the Queensland Government Department of Education and Training http://education.qld.gov.au/corporate/newbasics/html/pedagogies/pedagog.html.  The Productive Pedagogies are particularly designed for middle school environments and are particularly desirable for including diverse learners. and include sections of Intellectual Quality, Connectedness, Supportive Classroom Environment and Recognition of difference.  Anyone who has not come across these before READ THEM!!! makes a lot of sense and it would be great if these things were applied in every middle school classroom in the world
  • Very engaging and interesting unit – students of this age will particularly enjoy the DISASTER element of this class so most roads will lead to this element to ensure they stay engaged.
  • If I taught this unit I would also be engaged throughout the unit :O)
  • Community and indigenous involvement as well as connectivity to students’ local region (this could really be applied to any state in Australia since all states have either earthquake or past volcanic activity.
  • Caters for different learning styles
  • Contains various additions for extension students
  • Possibility for students to select assessment type – test or log book entries
  • Log book allows for continuous assessment – both formative and summative.  Serves as a guide to ensure students are not getting lost or on the wrong track.
  • The how volcanoes work website contains volcano quizzes and crosswords!!! these would be great for extension students.  Extension students could also work on their log book summaries and reflections if they finish any tasks early

Weaknesses:

  • Field trips could be time intensive.  Unit may need to be simplified if time requirements do not permit
  • I limited the amount of student choice when I was writing the teaching strategies – this would be dependent upon the class though – some would be more responsible if allowing students to choose their partners and assignment topic – others would take the situation to be a social event
  • Some of the co-operative learning techniques could be noisy
  • would be good to find a substitute demonstration for the volcanic eruption demonstration in the Explore phase, I have said to emphasis to students that we are talking about a physical change, rather than a chemical change but mixing bicarb and vinegar, at least in my head, reeks to much of chemical change and may be confusing…

Opportunities:

  • There is an opportunity to work collaboratively with other teachers with this unit.  Tsunami waves and seismic waves would make fantastic fodder for maths classes, There is an opportunity to connect this subject with history (either ancient or modern) and an opportunity to connect it with SOSE in looking at human impacts of natural disasters.
  • There is an opportunity to extend this unit to move into a life and living unit.  There is also an opportunity to extend the physics in this unit by focusing on energy conservation and transformation.
  • There is an opportunity to be flexible with assessment in this unit – to either make assessment through the learning log or through a test.

Threats:

  • Noise is a possible threat… A great tip was given by a teacher at a presentation I went to last year (horror upon horror but I can’t find her name…. sorry….) – she mentioned drawing a noise scale on the board and informing students they need to keep within an appropriate range – if they get to loud then mark the noise scale in red and bring it to the student’s attention they are being too noisy… maybe by clapping 3 times or something.
  • Explore activities could be messy… would be good if students wore lab coats perhaps…
  • Students involved in the Assessment 1 could have difficulties working with each other – or one student may be sick which may leave the other in the lurch.  If this occurs I would put the partnerless student in with the group who were covering the same Natural Disaster, if the student doesn’t wish to work alone (some students would opt for completing the assessment on their own if it was already part finished.

My objectives (to make sure I have fulfilled them all…) By the end of this unit I want students to be able to:

  1.  Recognise that a scientific theory is developed and refined over time through rigorous testing
  2.  Recognise the major tectonic plates on a world map
  3.  Recognise different boundary types and their properties (converging, diverging, transform)
  4.  Understand convection currents and their ability to drag lithospheric plates around
  5.  Understand how plate boundary activity leads to sea floor spreading, volcanoes and earthquakes
  6.  Recognise different kinds of volcanoes are due to different kinds of eruptions and the silica composition of the magma is responsible for the explosiveness of the eruption.
  7. Recognise hot spot activity may produce volcanoes and that hot spots stay relatively stationary, in comparison to the moving plates
  8. Recognise scientists’ roles in understanding, assessing and monitoring tectonic activity, the role of structural engineers in developing tsunami breaks and earthquake-safe buildings and how technological advances.
  9. Recognise the technology used in monitoring of earthquakes, tsunamis and volcanoes and how advances in technology have increased our understanding of plate tectonics
  10. Recognise Australia’s tectonic history, including around the Gold Coast, and acknowledge the indigenous perspectives of these events
  11. Understand how seismic waves, liquefaction and tsunamis occur

YEP!!! have covered all that (plus some perhaps…)

Reflection on this assignment:

  • I loved it!!! my favourite assignment of all time… I highly recommend doing the assignment either as a blog or as an individual wiki page – the advantage of a wiki would be that it could be better organised (you could move things about) – you can’t do that so well with a blog….
  • I have learned so much about geology and continue to bore my friends and family about the subject – I have also learned heaps about the Gold Coast’s history.
  • I want to acknowledge Harry Kanasa, Griffith University Gold Coast Campus, my tutor for 7034EPS who taught me many of the learning strategies used in the unit part of this blog… THANKS HEAPS!!! and also, my other lecturers and tutors at Griffith who have filled my brain with productive pedagogies, constructivism and all other kinds of beaut stuff!!!
Keep tuned for more exciting stuff on this blog… I have decided to keep it to review other science topics… 

I searched far and wide for Australian indigenous references to volcanoes and earthquakes… Of course the volcanoes in Australia have been long extinct so there are not great descriptions of angry gods living inside them, as there is in New Zealand and elsewhere.

Indigenous Australians see mountains as gods and they are place of religion and ceremony – to be cared for and respected.  Mount Warning is a local example.  The indigenous people have their stories about the volcanic formations in this region – like this fantastic one I found about our volcanic boulders at Burleigh Heads – as described on this fantastic website on the aboriginal history of the Gold Coast  http://www.janesoceania.com/australia_goldcoast_history/main.htm.

And into Paradise came a giant called Jabreen. Stretching out before him was an unbroken stretch of beach and dunes, so vast it stretched fom Kijeragah (a tree) at the mouth of a northern river (the Nerang), to a river far away in the south (the Tweed). though Jabreen was a spirit of the Gods, like any mortal who visits Paradise he was drawn irresistibly to the sparkling surf. Dropping his weapons he swam out to the horizon and back. When he picked up his huge war club or waddy, the ground still clung to it, rising up, following the waddy like iron follows a magnet. This created the rocky outcrops of Little Burleigh.   

I also found a dream time story about earthquakes – this lovely Dream-time story comes from the Awabakal language aborigines who lived around Newcastle, NSW.

The Kangaroo That Lives Inside Nobbys

http://ab-ed.boardofstudies.nsw.edu.au/index.cfm?objectid=0D95E350-E5E7-8A30-51EDBE588DBE7FA6

A very long time ago, when there were still giant sized animals around, all the various animals within the area would separate into two groups – one group being the females and the other the males.

They all lived together very peacefully and happily. 

One day a large male kangaroo attacked a female wallaby.

This was against the law.

He was banished from the kangaroo group forever.

After a long chase by the wallabies the kangaroo reached Muloobinba, the place of the sea ferns, now called Newcastle.

As he entered the sea, he thought about how lucky he was to be able to slip away from the wallabies that chased him.

The wallabies thought that he had drowned.

But the kangaroo had swum to Nobbys Island and entered the tall rocky outcrop, making sure that he was out of sight of everyone.

He is still there to this day, but he won’t come out because he is never sure if it is safe for him from the angry wallabies.

Sometimes he gets upset and jumps around inside his prison. When his giant tail crashes against the earth, it makes the rocks fall and the ground tremble.

The Awabakal people believe this is what causes an earthquake

I am also putting a further note about Australia in this post… most old stuff, and official text book entries, you read on Australia says we are relatively inactive when it comes to earthquakes, volcanoes and mountain building… We are hot and flat – and dry… this is because we are not near any tectonic plate boundaries.  The lack of tall mountain structures contributes to us being such a dry continent (the more mountains/ volcanoes the more rain you get…), and the lack of windbreaks/ protection has led to extensive weathering and erosion of the volcanic structures made, millions of years ago, when Australia passed over a hot spot.  Just recently some Australian geologists have started making a few waves by saying about 1000 years ago some event pulled some dormant faults in Australia out of dormancy.  These geologists say there is volcanic building activity (with a proposed minor hotspot being underneath Victoria) and mountain building (as a result of earthquake movement).  I finally found a good website with references on it with the opinions of these geologists!!! http://home.iprimus.com.au/foo7/volcmap.html#5 - goes into everything – including maps of predicted potential earthquakes and volcanoes.

Gosh I have learned heaps!!!  Geology was always something I was a bit evasive about (being a life scientist)… although I have covered rock types before (which students would have covered more thoroughly in year 8), and could draw the reactions to get from bauxite to aluminium – dug out of my brain from uni inorganic chemistry… I think I could happily go and get a degree in geology now that my interest has been sparked – maybe my enthusiasm is better spent encouraging students to do earth sciences!!!

Going back to my curriculum links mentioned previously…

The National Curriculum: Science / Year 9 / Science Understanding / Earth and space sciences

The theory of plate tectonics explains global patterns of geological activity and continental movement

Elaborations

  • recognising the major plates on a world map
  • modelling sea-floor spreading
  • relating the occurrence of earthquakes and volcanic activity to constructive and destructive plate boundaries
  • considering the role of heat energy and convection currents in the movement of tectonic plates
  • relating the extreme age and stability of a large part of the Australian continent to its plate tectonic history

Code ACSSU180

The Queensland State curriculum Science/ Year 9/ Knowledge and Understanding/ Earth and Beyond

Geological evidence can be interpreted to provide information about past and present events e.g. the earth’s surface is shaped by volcanoes and earthquakes, which can be understood in terms of the theory of plate tectonics.

I can safely say I am thoroughly equipped, knowledge wise, to do an entire unit on plate tectonics – in-fact I could easily do an interdisciplinary unit to bring in physics (volcanoes/earthquakes/tsunamis), maths (ditto), biology (effects of natural disasters on ecosystems and populations – haven’t covered that here but have a major in ecology from my first degree), social science (human impact/ laws and regulations/ economic impact), geography (mountain ranges/ the locations around the ring of fire…) and history (POMPEII… but also looking at the age and development of the earth through the different ages).

In order to ensure I develop teaching strategies to fit into the National Curriculum requirements I investigated the Year 9 science curriculum a little further to find links to other appropriate Science Understandings as well as where the understandings could link with Science as a Human Endeavour and Science Inquiry Skills.  See my notes in red on ideas.

From:  http://www.australiancurriculum.edu.au/Science/Curriculum/F-10

Year 9 Content Descriptions

Science Understanding

Earth and space sciences

1. The theory of plate tectonics explains global patterns of geological activity and continental movement (ACSSU180). Obviously, the main unit focus – the full description of this Science Understanding can be seen above.  This topic lends itself well to be the focus of an inquiry-based learning unit using a 5Es format.    Pedagogical content will be developed to allow students to gain a deep understanding of this subject.  Students would already have covered rock types in year 8 which will be connected to this unit when looking at the earth’s crust, seismic and volcanic activity.  Students would have some experience learning about sudden geological changes in year 6 “Sudden geological changes or extreme weather conditions can affect Earth’s surface (ACSSU096)”.  In ACSSU096 students would have learned about volcanoes, tsunamis and/or earthquakes and this will be used as an engage tool and as a starting point to assess students’ alternate conceptions.  

Physical sciences

1. Forms of energy can be transferred in a variety of ways through different mediums (ACSSU182)  There is opportunity to connect energy transfer with tectonics in a variety of places – including convection currents, seismic waves and tsunamis.  Tectonics would be a fantastic unit to do before a unit where energy transfer is covered more thoroughly (understanding real world applications of energy transfer before they learn the details).  Students already have some experience in year 8 with energy forms.  

Science as a Human Endeavour

Nature and development of science

  1. Scientific understanding, including models andtheories, are contestable and are refined over time through a process of review by the scientific community (ACSHE157)
  2. Advances in scientific understanding often rely on developments in technology and technological advances are often linked to scientific discoveries(ACSHE158)
    Both of these points fit in well to the development of tectonic plate theory – so will be addressed in the unit.  It will be important, when mentioning Weneger’s ideas, to emphasis HIS MECHANISMS proposed for continental drift were not right (to avoid student confusion…) – even though he was right about the continents moving (although, more accurately, it is plates which the continents are part of which move).  Technological advancements leading to knowledge of tectonics include 1950s sonar equipment, the development and world placement of seismic readers, and of course, most recently, GPS satellites.  

Use and influence of science

  1. People can use scientific knowledge to evaluate whether they should accept claims, explanations or predictions (ACSHE160)
    Maybe we can use some of the ridiculous claims in newspapers about the state of our fault lines as an example of how students can apply their scientific knowledge to accept or reject claims (like the one mentioned in the Earthquakes post).  Geologists, in the past, also used their scientific knowledge to reject Weneger’s ideas about the mechanism of continental drift- science did not support his theory.  
  2. Advances in science and emerging sciences and technologies can significantly affect people’s lives, including generating new career opportunities (ACSHE161)  This we will see along the way when talking about volcanologists, geologists, seismologists… And also how new technology, like tsunami monitoring devices, can help to warn people of tsunamis and save their lives.  
  3. The values and needs of contemporary society can influence the focus of scientific research (ACSHE228) A good example of this is researching Australia’s fault lines and geology to help develop mechanisms for predicting areas most likely to be effected by earthquakes and tsunamis.  Researching our geology can help to guide the development of building codes and warning strategies to allow people in higher risk areas to live more safely (as influenced by the Newcastle earthquake of 1989).  A further example is in Japan – because Japan is on a fault and is, therefore, an area of earthquakes, tsunamis and volcanoes – the majority of scientific research money in Japan is spent on earthquake and tsumami research.  

Science Inquiry Skills

Questioning and predicting

  1. Formulate questions or hypotheses that can be investigated scientifically (ACSIS164) It would perhaps be good to do an investigation into different soil types in an earthquake and how this could affect the stability of structures/ buildings/ roads 

Planning and conducting

  1. Plan, select and use appropriate investigationmethods, including field work and laboratory experimentation, to collect reliable data; assess risk and address ethical issues associated with these methods (ACSIS165)  See above – perhaps an investigation into different types of soils and earthquake impacts 
  2. Select and use appropriate equipment, including digital technologies, to systematically and accurately collect and record data (ACSIS166) See above investigation – tabulate data from investigation 

Processing and analysing data and information

  1. Analyse patterns and trends in data, including describing relationships between variables and identifying inconsistencies (ACSIS169)
  2. Use knowledge of scientific concepts to draw conclusions that are consistent with evidence (ACSIS170) This would be done in the investigation above, but also from questions given throughout the unit and recorded in log books.  

Evaluating

  1. Evaluate conclusions, including identifying sources of uncertainty and possible alternative explanations, and describe specific ways to improve the quality of the data (ACSIS171) Investigation above

Communicating

  1. Communicate scientific ideas and information for a particular purpose, including constructing evidence-based arguments and using appropriate scientific language, conventions and representations (ACSIS174) This will be evident at many points through the unit during class discussions, log book?, formative and summative assessment opportunities.  

The science achievement standard (from Australian National Curriculum website http://www.australiancurriculum.edu.au/Year9)

(appropriate parts in black)

By the end of Year 9, students use their knowledge to pose different types of questions that can be investigated using a range of inquiry skills. They apply their knowledge of science to explain phenomena in the environment and their own lives and describe how knowledge has developed through the work of scientists. They plan experimental procedures which include the accurate control and measurement of variables. They identify inconsistencies in results and suggest reasons for uncertainty in data. They use scientific language and representations when communicating their results and ideas.

Students use knowledge of body systems to explain how complex organisms respond to external changes. They use knowledge of interrelationships to describe how changes affect ecosystems. They explain geological features and events in terms of geological processes and timescales. They describe the structure of atoms and explain chemical changes in terms of the behaviour of atoms. They describe a range of chemical reactions and explain their importance. They compare, in qualitative terms, how two different forms of energy can be transferred. They describe interrelationships between science and technology and give examples of developments in science that have affected society.​


Looking further at Queensland state curriculum from the Queensland Studies Authority website http://www.qsa.qld.edu.au/downloads/early_middle/qcar_el_science_yr9.pdf.  Knowledge and Understanding in the Essential Learnings is also guided by the Ways of working (WoW).

Ways of working 

Students are able to:

•             identify problems and issues, formulate scientific questions and design investigations Earthquake investigation – see above 

•             plan investigations guided by scientific concepts and design and carry out fair tests Earthquake investigation 

•             research and analyse data, information and evidence Various points in explain/evaluate phase 

•             evaluate data, information and evidence to identify connections, construct arguments and link results to theory This could take the form of asking why volcanoes and earthquakes occur more often around plate boundaries.  Or picking a location and asking students to predict what geological activities would be common in that place given where it is situated in regards to types of plate boundaries.  

•             select and use scientific equipment and technologies to enhance the reliability and accuracy of data collected in investigations Perhaps this could be part of seismic reading investigations… 

•             conduct and apply safety audits and identify and manage risks could write that into an investigation…

•             draw conclusions that summarise and explain patterns, and that are consistent with the data and respond to the question analysis of data from investigation

•             communicate scientific ideas, explanations, conclusions, decisions and data, using scientific argument and terminology, in appropriate formats formative and summative assessment pieces 

•             reflect on different perspectives and evaluate the influence of people’s values and culture on the applications of science Australian indigenous people, along with many indigenous people from other nations, have religious associations with mountains and volcanoes and have developed rituals and superstitions to help live in harmony with these sacred places.  Australian indigenous people have developed stories to explain earthquakes and geological formations.  I think it would be worth having a local indigenous person give a talk on their perspectives of the Tweed Volcanic region during the course of this unit – even in the final class of the Evaluate phase perhaps when students are reflecting on the unit.  

•             reflect on learning, apply new understandings and justify future applications.  This would mainly be done in the elaborate/ evaluate phase of a 5Es unit – although may form part of summative assessment, and would to some degree be part of the reflection at the end of every class or section in this unit.  

Knowledge and understanding

Science as a human endeavour

•              Responsible, ethical and informed decisions about social priorities often require the application of scientific understanding – i.e. Should we live near volcanoes or in areas of high earthquake/ tsunami activity? What can we do to protect people who chose to live near these areas? Perhaps this is best in the explore phase 

Earth and beyond

•              Global patterns of change on earth and in its atmosphere can be predicted and modelled - e.g. Australia is moving north-east due to tectonic plate movement and is in the process of colliding with Asia.  We can predict areas of higher volcanic and seismic activity and potential effects this may have on weather patterns, acid rain, mountain building. 

•              Geological evidence can be interpreted to provide information about past and present events This is the main feature of this unit.  e.g. the earth’s surface is shaped by volcanoes and earthquakes, which can be understood in terms of the theory of plate tectonics.

Energy and change

•              Energy can be transferred from one medium to another see above

•              Transfer of energy can vary according to the medium in which it travels see above

•              Energy is conserved when it is transferred or transformed see above

See National curriculum notes above for links of energy concepts.  

Natural and processed materials

•              Changes in physical properties of substances can be explained using the particle model

This will be looked at during volcanism and convection currents – students would already have some experience in physical properties from previous years.  

This unit is perfectly situated to encourage an interest in Earth Science – offered as an Authority subject in years 11/12 in some schools.  This year 9 unit draws on year 7 Essential Leaning in Earth and Beyond “Changes to the earth occur over varying time periods and can be interpreted using geological evidence” and the year 5 Essential Learning in Earth and Beyond “Changes to the surface of the earth or the atmosphere have identifiable causes, including human and natural activity”.   As mentioned in National Curriculum notes above, these concepts will help to guide ways to determine alternate conceptions in the Engage phase of the unit.

Assessment

There will be more on assessment later on (see the elaborate and evaluate phase!!!).  In our 5E’s unit planning we did learn it was best to work out what you want the students to know, and how you are going to assess it, before writing the 5E’s.

so… What I want the students to know…

Combining facets of Knowledge & Understanding, Science as a Human Endeavor and Science Inquiry Skills listed above from the Australian National Curriculum, and the Essential Learnings Knowledge and Understanding and Ways of Working from the Queensland State Curriculum (QSA) above…

By the end of this unit I want students to be able to:

  1.  Recognise that a scientific theory is developed and refined over time through rigorous testing
  2.  Recognise the major tectonic plates on a world map
  3.  Recognise different boundary types and their properties (converging, diverging, transform)
  4.  Understand convection currents and their ability to drag lithospheric plates around
  5.  Understand how plate boundary activity leads to sea floor spreading, volcanoes and earthquakes
  6.  Recognise different kinds of volcanoes are due to different kinds of eruptions and the silica composition of the magma is responsible for the explosiveness of the eruption.
  7. Recognise hot spot activity may produce volcanoes and that hot spots stay relatively stationary, in comparison to the moving plates
  8. Recognise scientists’ roles in understanding, assessing and monitoring tectonic activity, the role of structural engineers in developing tsunami breaks and earthquake-safe buildings and how technological advances.
  9. Recognise the technology used in monitoring of earthquakes, tsunamis and volcanoes and how advances in technology have increased our understanding of plate tectonics
  10. Recognise Australia’s tectonic history, including around the Gold Coast, and acknowledge the indigenous perspectives of these events
  11. Understand how seismic waves, liquefaction and tsunamis occur

There is quite a bit of stuff to assess above so I suggest assessment in 2 parts:

Assessment piece – 50%.  Assessment piece 1 could take the form of a presentation.  Students could investigate a particular natural (e.g. Boxing Day earthquake/ tsunami); describe the science behind it and how technology or human intervention may prevent a future event being so devastating.   I would do this as a co-operative learning exercise and allow students to use multimedia or PowerPoint to do their presentation.  This could be done in friendship pairs or in teacher allocated pairs depending on the class.  English as a second language students and special needs students may benefit from the multimedia rather than face-to-face presentation format.  Disasters could be allocated to student groupings so that more complicated events were given to advanced students and students with learning difficulties could be given less complex (but still challenging) events (such as Christchurch earthquake or Newcastle Earthquake).  This assignment would assess a student’s ability to apply their knowledge to a new situation – i.e. describing their natural event in terms of what is happening with the tectonic plates, convection currents etc., right up to how the events are assessed in terms of magnitude and what can be done by humans / technology to reduce impact.  More details on this assessment piece will be put in the Elaborate or Evaluate section of this blog…

Assessment piece 2 – 50%.  For the second assessment, students could be given a choice of either handing in a learning log, completed throughout the course of the unit, or a test in the last class of the unit.  Both means of assessment would be suitable and a teacher may prefer to set one or the other depending on the class.  The learning log could be completed in a provided A4 exercise book or on a student’s laptop (if you have a 1 laptop per student learning environment) as a blog or a wiki.  The learning log would contain notes from the entire unit, a summary/ reflection written by the student at the conclusion of each lesson (homework) and answers to any questions given as homework.  A test, if preferred, would contain questions relating to each of the desired outcomes above.  Learning Logs, particularly when done on computer, can benefit learning disadvantaged and English as a second language students (because they can take their time compiling it) so would be the preferred method of assessment if these students are present in the class.  More details on how this will be assessed will be put in the Evaluate section of this blog …

The log book, regardless of whether it will be used as summative assessment, makes an excellent tool for formative assessment so students log books, blogs or wiki pages will be reviewed throughout the unit.

diagnostic assessment will also be carried out to determine students alternate conceptions, and level of understanding, prior to moving on from a task or activity.

THE QUIZ REVISITED!!!!

So following my last step of construction of my knowledge I revisited my quiz, which doesn’t look nearly as scary now – actually it looks totally inadequate for a quiz on the subject of plate tectonics…

The quiz, as mentioned previously, came from the Soft School website  http://www.softschools.com/quizzes/science/plate_tectonics/quiz415.html

1. The observation that the continents fit together like puzzle pieces, and may once have been connected, led Alfred Wegener to propose a theory in 1910 called

A: continental plowing

B: continental drift

C: wandering continents

D: shape matching of continents

obviously!!!

2. The essence of Wegener’s idea was sound, based on some scientific observations. Which of the following supported his theory?

A: Matching fossil plant remains found on two different continents

B: Matching reptile remains found on two different continents

C: nearly identical sedimentary rock types of same age in widely separated locations

D: all of the above

3. The development of submarine warfare druing World War II created a pressing need to map the ocean floor. This actually led to research on the ocean floor that would help explain the movement of the continents. What tool was used to do this mapping?

A: underwater cameras

B: sonar surveys

C: studies of living things

D: rock sampling

4. Scientists found that the continents were moving apart from each other due to magma rising out of mid-ocean ridges, and they called this

A: sea floor spreading

B: sea floor rising

C: changing sea floor

D: underwater volcanos

5. The Earth’s continents were once connected in one giant continent called

A: Eurasia

B: Indo-Australia

C: Pangaea

D: Pacifica

6. The Earth’s crust is divided into 7 major plates, which include all of the continents. Along which two plates do we see major earthquake activity?

A: Pacific and North/South American

B: Pacific and Eurasian/Indian

C: South American and African

D: A and B both

7. Wegener’s old theory, called sea floor spreading, was found too simplistic because it did not explain how the continents would move. It was replaced by a theory called

A: plate tectonics

B: crustal forces

C: paleomagnetism

D: weather forces

RED ALERT HERE!!!! the concept of sea floor spreading out from the earth splitting was mentioned by Wegener as a possible cause of continental drift – he did not have a theory called sea floor spreading – he wrote about the possibility in one paper and then moved onto other things so I have read… I thought it was Harry Hess, 30 years after the death of Wegener, who proposed sea floor spreading as a mechanism for continental drift and was instrumental in forming tectonic plate theory…

perhaps they should have made the question about his continental drift theory…

8. Plate tectonics is our current theory of how the movement of continental masses relates to the movement of ocean basins. This movement explains many phenomena, such as

A: earthquakes

B: volcanoes

C: weather patterns

D: all of the above

9. Plate margins are places where much activity occurs. Earthquakes occur, for example, along convergent margins, where plates are

A: moving apart

B: sliding past each other

C: colliding

10. Volcanoes occur in similar locations to earthquakes, and are common along plate boundaries. Sixty percent of volcanoes occur surrounding the Pacific Ocean, a location called

A: “the hot zone”

B: “the Ring of Fire”

C: “the Volcano Zone”

11. Plate tectonics can also be the direct cause of forming

A: lakes

B: streams

C: mountains

D: oceans

12. Plate tectonics, or the movement of pieces of Earth’s crust, is thought to be caused by

A: volcanoes

B: earthquakes

C: convection currents in Earth’s mantle

D: hot spots

Theme :               Plate Tectonics Science Quizzes                              Result: 12/12       

Number               Actual   Your Answer(s)

Review – 1           B             B

Review – 2           D             D

Review – 3           B             B

Review – 4           A             A

Review – 5           C             C

Review – 6           D             D

Review – 7           A             A

Review – 8           D             D

Review – 9           C             C

Review – 10         B             B

Review – 11         C             C

Review – 12         C             C

WOOOHOOO!!!! 100% AND I DIDN’T EVEN NEED TO GUESS ANYTHING… AND I COULD EASILY HAVE WRITTEN AN ESSAY EXPLAINING THE ANSWER TO EVERY QUESTION…

 Now for teaching this stuff to year 9s!!!


I have already read lots of stuff about earthquakes already so I know a fair amount like

  • Earthquakes mostly occur along tectonic plate boundaries due to convergent, divergent or transform movement
  • They can happen during or prior to volcanic activity

The definition of an earthquake – from Encyclopedia Britannica http://www.britannica.com/EBchecked/topic/176199/earthquake is:

  • earthquake -  Sudden shaking of the ground caused by a disturbance deeper within the crust of the Earth.

Doesn’t really tell me much I don’t already know – an earthquake is when the earth quakes or shakes about.  

Earthquakes are generally classified by most references as 2 distinct types - tectonic and man-made.

Tectonic Earthquakes:  

These are the ones that occur because of tectonic plate movement – and in some cases from lava/ magma movement within a volcano.

Earthquakes mainly occur at tectonic plate boundaries – and can happen at all 3 types of boundaries – the converging, diverging and transform.  Earthquakes can also occur intra-plate, like in here in Australia where we get around 200 earthquakes per year.

So why exactly do they happen???

A good explanation I found – with a video is found on the OIKOS website http://www.e-oikos.net/gmap/eng/Eq/EqMec.html?lingua=en-GB

This website talks about the sudden release of elastic energy from plate movement.  Elastic energy I know about from physics – this is a form of potential kinetic energy, from a material being distorted or pulled out of its natural shape – when tension is released the material loses potential energy to the environment.

To relate this to earthquakes…

Tectonic plate movement occurs on a continual basis – it pushes plates together, pulls them apart or makes them slide along side each other.  Rocks are not very slippery, there is an enormous amount of friction between them, so they do not take to being moved all that easily.  It is thought that during tectonic plate movements, the plate doesn’t move fluidly – stress builds up between the plates and when the tension is great enough to overcome friction there is a rapid movement of the crust to a place of lower stress.  The potential or elastic energy that had built-up in the straining rocks is then released into the environment.  The energy released can be small to extremely large depending on the amount of stress/ potential energy there was in the rocks.  The energy is released into the environment as seismic energy and is the cause of earthquakes.   Stress is designated as tensional, compressional or shear depending on the type of movement in the fault.

http://earthquake.usgs.gov/learn/glossary/?term=tensional stress

Rather than using the terms diverging, converging and transform – lots of websites classify the faults as normal, reverse or strike slip.  
Alternatively, some classify faults as either dip-slip or strike slip.
 To relate these to terms I know already…
  • At divergent plate boundaries/ constructive plate boundaries normal dip-slip faults occur.  In this type of fault the plates/ pieces of rock are generally being pulled apart causing tensional stress.  In many cases there is a hanging wall that slides down relative to the footwall as the earth’s crust lengthens.
  • At convergent plate boundaries/ destructive plate boundaries, reverse dip-slip faults occur.  In this type of fault the plates/ pieces of rock are being pushed together causing compressional stress.  In many cases there is a hanging wall that gets pushed up relative to the footwall as the crust shortens.  We of course have mentioned all this before when talking about subduction at converging plate boundaries.
  • At transform plate boundaries, strike slip faults occur.  In this type of boundary the plates/ pieces of rock are pushed transverse to each other causing sheer stress.
gosh – well considering the only place I have heard these names of normal/ reverse, dip-slip and strike-slip is in earthquake stuff – but it really refers to plate movements I have covered already.  It seems these names were generated before tectonic plate theory perhaps, which could explain the disjointedness.   But perhaps I will come up with another explanation with more research…
                                                                                                                                                                                                                                                                                  There is a map below that shows all the earthquakes that have been over 5.5 magnitude (I need to read about what the magnitude means!!!) on the world map.  Looks like the majority of them occur at tectonic plate boundaries (which we knew already).  From the map you can also see that convergent plate boundaries, as you would expect, are generally associated with the deepest focal points (e.g. you can see red/green around the north west Pacific plate and east Nazca plate – both regions of subduction/ converging plate boundaries.   (from http://www.ldeo.columbia.edu/LCSN/Eq/Global/seismicity.html)

 

So… I need to know…. what is going on at the spots not on the plate boundaries (there are not many of them, but they do exist… including, importantly, in our beloved Australia)… and I need to know what seismic activity is in scientific terms…

First of all… what is going on intra-plate – like in Australia…

It seems in 2008-2009 there was a boom in newspaper articles about Australia’s fault lines… being newspaper articles some were not terribly believable – like the Perth Sunday Times with their article “WA sits on deadly fault line” and continues with “ONE of the world’s biggest fault lines runs through WA’s back yard”.   Now that I know lots about tectonic plates, I can be safely assured that the statement is total cods-wallop since we do not have a major plate boundary running through this country http://www.perthnow.com.au/news/western-australia/wa-sits-on-deadly-fault-line/story-e6frg14u-1225782494162

We do have some minor faults running through Australia though (some of them quite extensive) – as they do the rest of the world.  There is good info about why on the Geoscience Australia website http://www.ga.gov.au/hazards/earthquakes/earthquake-basics/where.html

A minor fault, as opposed to a tectonic plate boundary major fault, is an area of fracturing of the earth’s crust bought about by stress of some kind.  The plates of the world have been moving about, pulling away from each other, slamming into each other and slipping past each other for millions of years.  Over the years, large plates have fractured from excessive stress and strain into smaller plates.  Australia has been pushed away from the Antarctic and up towards the Eurasian plate through tectonic plate movement (Sea floor spreading) – GPS data shows Australia is moving 35 degrees east of north with a velocity of 67 mm/yr.  This pushing from the sea floor spreading is slamming our Indo-Australian plate into the Eurasian plate.  As this pushing occurs, the Himalayas, the mountain range formed at the boundary of the Eurasian plate, gets taller and the Indo-Australian plate slips further under the Eurasian plate (through subduction at the converging plate boundary).  The resulting strain on the Indo-Australian plate from this continuous plate movement has been enough to cause a massive fracture in the plate which, it is thought, will eventually split the plate between India and Australia.  The Indo-Australian plate also forms a convergent boundary with the Pacific plate and a divergent boundary with the Atlantic plate, which adds to the push and pull stress.  The stress/tension can be felt at places other than the boundaries and, as a result, has resulted in small fractures forming in the crust all over the plate.  These fractures are called minor faults and, as with major faults, they can result in earthquakes from the release of stress in moving rocks/crust.  Australia is not unique in having these minor faults, they occur in every plate as a result of similar mechanisms.  These minor faults have the same slipping and sliding patterns described above – i.e. normal and reverse dip-slip faults and slip strike faults (Ahhhh – that makes sense… possibly why they call them different names than when just talking about the 3 kinds of plate boundaries!!!)

While all fault lines, including the ones in Australia, have the potential for seismic activity, the seismic activity as a result of minor faults is mild compared with major fault lines.  We have, in Australia, had a few large earthquakes.  Adelaide in South Australia is considered to be the most earthquake prone capital city in Australia – this is because South Australia bears the brunt of the slight sideways pushing.. Western Australia has quite a large fault which is prone to earthquakes but it is situated in a particularly remote area so generally does not cause widespread damage.  Australia’s most destructive earthquake occurred in Newcastle NSW in 1989 where 13 people were killed and 160 injured – it was estimated to have done about 4 billion dollars damage and is the first (and only) recorded earthquake ever to have taken a life in Australia.  This earthquake was calculated to have a magnitude of around 5.3.

This earthquake triggered the government into action monitoring and assessing earthquake activity in Australia and researching strategies to reduce potential damage in the future – there is some fantastic information on planning to reduce hazards on the Geoscience Australia website http://www.gs.gov.au - talking about building codes and soil types etc.

It is time to know more about seismic waves

What are seismic waves?  Well I found this great explanation of seismology here http://www.geo.mtu.edu/UPSeis/waves.html.  UPSeis is an educational website for budding seismologists!!! (got to love the internet…) bought to us by Michigan Technical University.

Seismic waves, as I have worked out already, is the energy formed from the breaking of rocks in the earth’s crust, or the energy released from elastic potential energy of rocks being subjected to stress in the earth’s crust, or from an explosion in the earth’s crust.

Seismic energy travels through the earth in waves is recorded by seismographs at seismic recording stations which are situated all over the world.  There are two distinct classes of seismic waves: body waves and surface waves.

Body Waves:  These can travel through the crust and mantle of the earth – they are higher frequency and travel faster than the surface waves.  There are two kinds of body waves; P waves and S waves.

P waves= also called primary waves, compressional waves or longitudinal waves.  These are the fastest kind of wave and will, therefore, reach the seismic reader first.  P waves take the push and pull form of sound waves and can travel through solid, liquid or gas at the speed of sound.  With P waves, particles move in the same direction of the wave/ energy.  Dogs can sometimes hear P waves and will start barking just before the full force of an earthquake is felt.

An animated version of this picture can be found here… http://www.geo.mtu.edu/UPSeis/images/P-wave_animation.gif

S waves = also called secondary waves, transverse or shear waves.  These are the second fastest kind of wave, being about 60% of the speed of a P wave, and can only travel through rock/ solids not liquids or gases (since liquids and gases do not support shear stress).  S waves move particles like light waves – up and down or side to side, perpendicular to the direction the wave is travelling.

An animated version of this picture can be found here… http://www.geo.mtu.edu/UPSeis/images/S-wave_animation.gif

Surface Waves:  These, as the name suggests, travel only through the upper crust of the earth’s lithosphere.  Surface waves travel more slowly, at approximately 90% of the speed of S waves.  Surface waves have a lower frequency and higher amplitude than body waves and are responsible for the physical destruction caused by earthquakes.  There are two kinds of Surface waves; Love waves and Rayleigh waves.

Love waves – These are slightly faster than Rayleigh waves and move the surface crust from side to side – they can make water vibrate a little but not to any great degree

An animated version of this picture can be found here… http://www.geo.mtu.edu/UPSeis/images/Love_animation.gif

Rayleigh waves – These waves roll along the ground like a wave rolls along the water.  Rayleigh waves cause the earth’s surface to roll up and down and side to side and, despite being a lower frequency, can be much larger than other waves.  Rayleigh waves can travel through water and rocks…

An animated version of this picture can be found here… http://www.geo.mtu.edu/UPSeis/images/Rayleigh_animation.gif

You can see by looking at the animations why Rayleigh waves are going to be destructive!!!

The velocity and propagation of the wave depends on the density and elasticity of the medium.  When an earthquake occurs, the seismographs closest to the earthquakes epicenter records the S and P waves – from the pattern they can give an indication as to where the earthquake occurred.  In the event of an earthquake happening in sea or a long distance from seismic equipment, data of P waves from several surrounding recorders can be used to determine where the earthquake was.

An earthquake has an epicenter – this is the earths surface at the point where the earthquake occurred.  The focal point or focus or hypocenter of an earthquake is the point in the crust below the epicenter, where the rock movement that generated the earthquake occurred.

Earthquakes are measured in magnitudes based on the data received from the seismograph.  The data is used to scale earthquakes in order of severity.  Different countries use slightly different scales – in Australia, Geoscience Australia  http://www.ga.gov.au/hazards/earthquakes/earthquake-basics/where.html# describe the scale as follows

The size of earthquakes is determined by measuring the amplitude of the seismic waves recorded on a seismograph. A formula is applied to these which converts them to a magnitude scale, a measure of the energy released by the earthquake. For every unit increase in magnitude, there is roughly a thirty-fold increase in the energy released. For instance, a magnitude 2.0 earthquake releases 30 times more energy than a magnitude 1.0 earthquake, while a magnitude 3.0 earthquake releases 900 times (30×30) more energy than a magnitude 1.0.

A magnitude 8.6 earthquake releases energy equivalent to about 10,000 atomic bombs of the type developed in World War II.

The effects of an earthquake depend on many factors, such as the distance from the epicentre (the point on the Earth’s surface directly above where the earthquake originated within the Earth) and the local ground conditions. Generally, for locations near the epicentre, the following effects may be observed:

       
Magnitude Description  of effect
less  than 3.4
Usually  felt by only a few people near the epicentre.
3.5  – 4.2
Felt  by people who are indoors and some outdoors; vibrations similar to a passing  truck.
4.3  – 4.8
Felt  by many people; windows rattle, dishes disturbed, standing cars rock.
4.9  – 5.4
Felt  by everyone; dishes break and doors swing, unstable objects overturn.
5.5  – 6.1
Some  damage to buildings; plaster cracks, bricks fall, chimneys damaged.
6.2  – 6.9
Much  building damage; houses move on their foundations, chimneys fall, furniture  moves.
7.0  – 7.3
Serious  damage to buildings; bridges twist, walls fracture, many masonry buildings  collapse.
7.4  – 7.9
Causes  great damage; most buildings collapse.
greater  than 8.0
Causes  extensive damage; waves seen on the ground surface, objects thrown into the  air.

There are seismic recording stations ALL over the world… A list of them can be found  here http://www.iris.edu/data/DCProfiles.htm.  This includes our own recording sites in Australia.

Earthquakes often do not occur as isolated events.  When you have a large earthquake it is common to have smaller adjustments/ earthquakes at the same point or very close over several days.  In this event the subsequent earthquakes are called aftershocks. Earthquakes can also occur in clusters, where you can see many earthquakes near each other but no one earthquake is of significantly higher magnitude than the others, or in swarms, where one earthquake triggers fault activity at a different site and triggers subsequent earthquakes.

Man-Made Earthquakes:

Seismic activity can be triggered by explosions and bombs – A good explanation I found on the Michigan Technical University website UPSeis http://www.geo.mtu.edu/UPSeis/why.html:

  • “Earthquake-like seismic waves can also be caused by explosions underground. These explosions may be set off to break rock while making tunnels for roads, railroads, subways, or mines. These explosions, however, don’t cause very strong seismic waves. You may not even feel them. Sometimes seismic waves occur when the roof or walls of a mine collapse. These can sometimes be felt by people near the mine. The largest underground explosions, from tests of nuclear warheads (bombs), can create seismic waves very much like large earthquakes. This fact has been exploited as a means to enforce the global nuclear test ban, because no nuclear warhead can be detonated on earth without producing such seismic waves.

There are also some references to man made activity near faults triggering earthquakes.  Some geologists appear in favour of this being possible, although it is not mentioned at all on many geological websites so the hypothesis possibly doesn’t have enough substantial evidence to support it totally.  The man made activities thought to be responsible, by some, for triggering earthquakes, includes damming and mining near fault lines.  Some of the major earthquakes postulated to have been “man triggered” include the 2008 earthquake in Sichuan, China that killed 80,000 people – the earthquakes epicenter was just 550 yards from a dam holding 315 million tonnes of water – from the UK Telegraph (http://www.telegraph.co.uk/news/worldnews/asia/china/4434400/Chinese-earthquake-may-have-been-man-made-say-scientists.html).    Closer to home, the Newcastle Earthquake was the subject of a review by Christian D. Klose of Columbia University’s Lamont-Doherty Earth Observatory in Palisades, New York (http://www.abc.net.au/am/content/2007/s1823833.htm), who linked 200 years of underground coal mining,in Newcastle to the reactivation of a fault and the trigger of the 1989 earthquake that killed 13 and caused around 1 billion dollars worth of damage.  The hypothesis is that these man-made activities can be the trigger of adjustments in rocks at fault lines or can contribute to increased stress near fault lines.  The debate is still out on this but I am sure we will hear more about it in the future…      

oooh oooh oooh – I just found reference to this on Geoscience Australia – but not in the section on what causes earthquakes.  It said coal mining in Newcastle could have been a potential trigger for the 1989 Newcastle earthquake. 

SO… Interesting knowing the theory… and gosh – I have seen the effect on TV!!! with the Christchurch NZ earthquake and the Japanese earthquake… The two things that struck me about these earthquakes… with the Christchurch one it was the mud bellowing up through cracks in the roads/ ground, and with the Japanese one… THE TSUNAMI!!! massive wave… These would be classified as effects of earthquakes… Along with shaking and landslides which also occurred in New Zealand.  

Effects of Earthquakes:

 Aside from obvious damage bought about by the ground shaking and rippling with the surface waves, which naturally can cause extensive damage to structures such as buildings, houses, bridges and roads (also, of course, what is in and on these structures).  There are a few other less direct things that can cause damage from earthquakes.   

Liquefaction

This is what that muddy stuff was that was oozing out of cracks in New Zealand following the Earthquake a couple of months ago.  Liquefaction of silt it was…

A good explanation of liquefaction can be found here http://www.es.ucsc.edu/~es10/fieldtripEarthQ/Damage1.html - in summary it says that liquefaction occurs when saturated sandy, silty or gravelly soils are exposed to seismic shear waves during an earthquake.  The seismic waves change the properties of the soil so it behaves more like a viscous liquid or cement slurry than a solid.  Hydrated soil normally has a consistent amount of strength to support its structure – due to the grains physically touching each other and from the consistent water pressure between the pores.  Seismic waves cause the soil particles to vibrate and, as a result, the water is forced out of the soil particles into the pores – thus increasing water pressure between the grains.  The process continues as earthquake vibrating continues – constantly reducing the soils ability to “stick” together and eventually allowing it to collapse into a liquid (i.e. it loses shear strength because of the lack of interaction/ friction between the grains).  Because the water pressure has increased significantly, the liquid also wants to escape… and because of this it will often spurt up through cracks formed by earthquake activity (called sand volcanoes).

This picture from http://www.semp.us/publications/biot_reader.php?BiotID=330 provides a great diagram of the soil grain interactions.  If there are houses, roads, bridges or buildings built on sandy/ silty or gravely soil then liquefaction could be a potential nightmare because the once solid surface suddenly turns into a liquid.  Liquefaction is one of the main causes of structural damage from earthquakes because it can cause entire buildings to sink and topple over.  Luckily Christchurch, built on hydrated silt, was aware of its potential for liquefaction prior to the 2011 earthquake, so their building code ensures it is considered in newer buildings and houses.  There was extensive liquefaction flooding in yards and many roads and some bridges in Christchurch were destroyed as a result of liquefaction – but this could potentially have been far worse without the building codes.  There is an excellent video which explains the cement-like properties of liquefied silt here http://mandenomusings.wordpress.com/2011/03/03/christchurch-earthquake-liquefaction-explained/

Manden, in this blog, uses the analogy of a tent to describe the liquefaction process – if you take the inside frame out of a tent then it collapses and no longer has any shear strength – being more like a liquid…

In the video above, a guy puts the solid looking wet silt into a wheelbarrow and wheels it out of his front yard – by the time he gets to the front it is liquid again due to the bumping motion of the wheelbarrow on the brick paving.  This is a good demonstration of the structure – when stationary it appears solid, when moving it turns into liquid.  

Another cause of destruction from the 2011 Christchurch earthquake was landslides

Landslides

Landslides are just what they sound like – slippage of part of the structure of a hill or mountain.  Landslides can be caused by destabilization through shaking, can be caused by rock crushing near the earthquake epicenter or can also be due to liquefaction.  The earthquake, particularly if at a converging plate boundary, can contribute significantly to the height of a mountain within a few short seconds – this can also be enough to destabilize the mountain and cause major avalanches/ landslides.   There were two major landslides resulting from the 2011 Christchurch earthquake.  Landslides and avalanches can cause extensive damage to houses and roads and if they are large enough and fall into a body of water they may even potentially trigger tsunamis.

Tsunamis

On Boxing day in 2004 a 9.1 magnitude earthquake occurred off the coast of Sumatra, Indonesia (n.b. this is in the ring of fire and was at a subduction zone…).   The earthquake triggered a series of deadly tsunamis that killed over 200,000 people in 12 countries with waves up to 30 meters high.  Those of us who remember this earthquake were horrified by the numbers of dead and missing, and until this time I had NEVER heard of a tsunami.  So what is it exactly, aside from a giant wave…

Well Geoscience Australia does quite a good job trying to explain tsunamis http://www.ga.gov.au/hazards/tsunami/tsunami-basics/what.html as does the EarthScience website at http://earthsci.org/education/teacher/basicgeol/tsumami/tsunami.html.  Tsunamis can be triggered by anything with the potential to displace large amounts of water in the ocean.  This would include earthquakes under or next to oceans, landslides/ avalanches, volcanoes or meteorites hitting the ocean.   The most common cause of tsunamis are underwater earthquakes with a magnitude over 6 (cause around 3/4 of all tsunamis) occurring underwater at subduction zones (converging plate boundaries).

I like the idea of the step-by-step to tsunami… this has helped me understand what it is all about…

1. Initiation!!!   [ Image of Tsunami Generation ]

During a large submarine earthquake there is a rapid jolting/ displacing of a column of water upward.  For the case shown above, the earthquake rupture occurred at the base of a subduction zone in deep water. Note: In the figure the waves are greatly exaggerated compared to water depth! In the open ocean, the initial tsunami wave is at most, several meters high.

2. Split!!! [ Image of Tsunami Wave Split ]

Within several minutes of the earthquake, gravity splits the initial tsunami into two separate tsunami waves which travel in opposite directions – one that travels out into deep ocean and the other that travels towards the nearby coast.  The two tsunami waves are approximately half the height of the original wave.  The speed which the tsunami waves are travelling at depends on the depth of the water the wave is travelling according to the following the equation

c is equal to the square root of gH where c = the speed of the wave, g is the acceleration due to gravity (= 9.8 m/s2) and H is the depth of water.

i.e. from this we can see that tsunami waves travel more quickly in deep water – if we are talking about water 4000m deep, which would be common, the tsunami wave is travelling at 198m/sec.  The deep water tsunami will travel faster than the tsunami near shore.

3. Amplification!!! [ Image of Tsunami Amplification ]

As the tsunami travels over the continental slope towards land, the sea depth (H) gets smaller – and as a result of the equation above, the hight (amplitude) of waves increases (since the energy of the tsunami is maintained) and the tsunami waves slow down (the wavelengths decrease).   Note that the deep ocean tsunami has travelled much farther than the local tsunami because of the higher propagation speed (again because of the equation above). As the deep ocean tsunami approaches a distant shore, amplification and shortening of the wave will occur, just as with the local tsunami shown above.

4. Run-up!!! [ Image of Tsunami Runup ]

As the tsunami wave travels from the deep-water, to the near-shore region, tsunami run-up occurs. Run-up is a measurement of the height of the water onshore observed above a reference sea level. Contrary to many artistic images of tsunamis, most tsunamis do not result in giant breaking waves (like normal surf waves at the beach that curl over as they approach shore). Rather, they come in much like very strong and very fast tides (i.e., a rapid, local rise in sea level). Much of the damage inflicted by tsunamis is caused by strong currents (in and out, and floating debris. The small number of tsunamis that do break often form vertical walls of turbulent water called bores. Tsunamis will often travel much farther inland than normal tidal waves.  Because of the amplification and slowing down process, some of the shore water is sucked in help amplify a tsunami wave – this is why it is often mentioned that the water disappears from the beach before a tsunami hits.  Tsunamis are associated with lots of energy – after run-up part of the tsunami energy is reflected back to open ocean and can generate edge waves that travel back and forth, parallel to the shore.  As a result of long wavelength and ability of tsunami to transfer energy, a second tsunami wave often occurs which is larger than the first (not always the case but does sometimes happen.

Tsunamis are often inconspicuous at sea – since they are really quite shallow in deep water- often only a meter tall.  Because earthquakes are rather unpredictable, tsunamis are unpredictable – but measuring instruments can measure changes in water which may indicate a tsunami, and these measuring instruments have been situated near the coasts of Australia to give us some forewarning.  Seismic activity is also measured to help us monitor earthquakes that have the potential of generating tsunami waves which may affect us.  Tsunamis have drowned hundreds of thousands of people and animals in the past decade and have caused more destruction than any other natural events.

oh another note on tsunamis I read somewhere – the shallower the underwater (submarine) earthquake, the more potential for the tsunami… this is actually pretty logical…

All because of a simple equation huh!!! tsunamis would make a good maths class 

Mountain Building

This isn’t necessarily a bad thing – like the other consequences of earthquakes.  Earthquakes are a result of moving and cracking rocks – if this movement involves an upward displacement of rock (like with subduction zones or dip-slip faults), then you have mountain making occurring.  A large scale example of this is the Himalayas at the convergent plate boundary – a small scale of this is in our own backyard – it is thought there is some very slow active mountain building going on in South Australia as a result of minor dip-slip fault activity.  http://cooberpedyregionaltimes.wordpress.com/2008/09/26/faultlines-weaving-their-way-across-southern-australia/ is an interesting newspaper article on this – written for the Coober Pedy Regional Times Newspaper.    The mountain building is occurring very slowly.
Mountain building most commonly occurs when convergent boundaries meat on land rather than the usual case of oceanic crust and continental crust.
SO… that ends my earthquake investigation… the other thing interesting to note… is the monitoring of earthquakes http://earthquake.usgs.gov/earthquakes/recenteqsww/ This is the most fantastic site!!! it is a map of earthquake activity up to the current time – showing all earthquakes in the world that have happened in the last hour – day – week and their magnitude… FASCINATING… Earthquakes are monitored very closely in an effort to make some predictions about when and where they may occur.  While they are unpredictable, many faults have a certain amount of regular activity… if the activity begins to slow down or stops then it is thought there is potentially lots more stress building up in the fault which leads to the possibility of a major earthquake.  We have earthquake monitoring going on in Australia – and we have earthquake safe building codes in most places now – much of this was triggered by the 1989 Newcastle earthquake which gave evidence to how poorly prepared Australia was for such an event.    There is an earthquake overlay in Google Earth which is a fantastic learning tool – it links to this website.  There is a more specific Australian version of this earthquake monitor on the Geoscience Australia website http://ga.gov.au/earthquakes.

So how would I teach students about earthquakes… well I think I would start out by getting them to explore where they occur – where the biggies more often occur, what is meant by magnitude and perhaps do an activity where we simulate an earthquake and tsunami – best done in the explore phase… then cover the more detailed information about seismic readings, liquefaction, how tsunamis work and how they are monitored in the explain phase… perhaps adding to the jigsaw activity previously mentioned… 

This knowledge can then be used to look at seismic activity in Australia and what Australia is doing in the way of disaster management.  



So I am now pretty cluey on all the tectonic/ volcano connection stuff – super interesting – but there is other stuff about volcanoes I don’t know – like how they are classified and what actually comes out of them??? Although I do know that the stuff that comes out of volcanoes at hot spots and divergent faults is usually slow moving basalt type stuff…

So in the previous section I have mentioned fissure volcanoes, rift volcanoes, shield volcanoes and stratovolcanoes – are their more kinds of volcanoes?

A study of 10 different internet sites and 2 text books tells me that there is really not a clear classification system for volcanoes since almost all the websites have said totally different things – even the extremely reputable university based websites and the US geological survey say different things about classification… So I have decided to tackle this section based on what Geoscience Australia use as there classification but to also mention other “types” mentioned elsewhere.  The discrepancy in listed types of volcanoes is going to effect the way this stuff is taught… if this is being taught by a webquest, or a research type activity – it will be important that the information students are exposed to are consistent… i.e. probably need to tell them what links to look at and print out other resources for them that show consistent names…

Geoscience Australia can be found here http://www.ga.gov.au/hazards/volcano/volcano-basics/what.html.

Geoscience Australia classify the 3 kinds of volcanoes as Shield Volcanoes, Composite or Stratovolcanoes and Caldera volcanoes. Other websites also mention Scoria or Cinder cone volcanoes, Fissure volcanoes and Fumaroles.

A volcanoes appearance is going to be a result of what comes out of it and how it comes out.

What I know so far…. What comes out of a volcano is known as lava… it is derived from the earths mantle where it is known as magma until it reaches the surface.  Gases also come out of volcanoes – these gases were previously dissolved into the magma.  I know that volcanoes in hots pots (e.g. Hawaii) and divergent plates (e.g. Iceland/ Oceanic Ridge) are usually Fissure volcanoes and Shield volcanoes – are usually non-explosive and involve large amounts of mainly basaltic liquid magma.  I know Volcanoes at converging plates are usually explosive and the lava is more viscous and contains a mix of molten material from the mantle and molten rock/ minerals and water from the earth’s crust.  I know that Stratovolcanoes are common in these areas and they are built from layers of lava and tephra – which are fragments/ particulate matter resulting from the explosion – and that the explosion is more severe due to the nature of the magma pooling under the volcano.

Shield Volcanoes (and fissure volcanoes) and Basalt Lava: 

As mentioned, lava from Shield volcanoes (and fissure volcanoes) is usually very hot and runny.  This is because it is made from Basalt, otherwise called Mafic lava.  Basalt has a high content of iron and magnesium and a low content of aluminium and silica compared with other types of lava.  Aluminium, silica, calcium and many other dissolved minerals (but most significantly silica) will polymerize in hot magma and the polymerization alters the flow capacity making the lava much more viscous.  With the lowest levels of silica and very hot temperatures of up to 1200°C, basalt lava has the lowest viscosity of all lava types.  Because of the shallow slopes of shield volcanoes and the fact that the lava is still quite a lot more viscous than water, humans can still usually outrun lava flow from shield and fissure eruptions.

Shield volcanoes (and fissure volcanoes) generally erupt gently and are non-explosive because the low viscosity of the magma allows the various gases dissolved in the magma to escape easily when the magma reaches lower pressure areas at the earth’s crust.  So what gases are we talking about??? Well the majority is water vapor (around 60%) and carbon dioxide (10-40%) – particularly at subduction zone volcanic activity which usually involves molten oceanic crust being added to the magma from the mantle.  Subduction zone volcanoes usually also have lots of chlorine gas (from salt water NaCl.H2O).  Other gases dissolved in magma include nitrogen, sulphur dioxide (SO2), hydrogen sulphide (H2S), argon, helium, neon, methane, carbon monoxide.  Small amounts of hydrogen chloride, hydrogen flouride, hydrogen bromide, nitrogen oxide, sulphur hexaflouride and organic compounds such as the highly toxic methylmercury, halocarbons (like CFCs) and halogen oxyradicals.  (from  H. Sigurdsson et al. (2000) Encyclopedia of Volcanoes, San Diego, Academic Press).  So as a divergence… one thing that strikes me as hugely obvious about these gases… many greenhouse gases and contributors of acid rain!!!  Also lots of pretty toxic and stinky polluting gases in there like H2S, rotten egg gas… which is my experience of volcanoes… they reek of rotten eggs…

My favourite volcano, Kilauea volcano in Hawaii that has been erupting constantly since 1983, lets out heaps of sulphur dioxide gas (a major contributor of acid rain)

Kilauea volcano, Hawaii

So from our previous notes – Fissure volcanoes and Shield volcanoes are going to have a similar composition of magma and will have a similar eruption pattern.  The eruption pattern from these volcanoes is normally termed “Hawaiian” – a Hawaiian eruption means lava will typically spurt a little way into the air and then run down a mountain or pool into a lake (like the picture of Kilauea above).

Stratovolcanoes and andesite/ felsic lava:

Stratovolcanoes, as mentioned, are usually explosive and made up of layers of lava and tephra – were tephra is particulate matter resulting from the explosive eruption.  The lava from Stratovolcanoes (also called composite volcanoes) is composed of a mixture of the iron/ magnesium rich mantle, and a variety of minerals/ molten rock/ water from the lithosphere which has subducted at the convergent plate.  The lava from Stratovolcanoes is generally richer in silica, calcium and other minerals as apposed to basaltic lava – as a result, there is some polymerization of minerals and a higher viscosity to basalt lava.  Lava from stratovolcanoes is usually either andesite lava or felsic lava (rhyolite/ dactite).  Felsic lava is composed of rhyolite or dactite and has the most silica and therefore the most polymerization and highest viscosity.  Andesite has a lower level of silica and polymerization but is still far more viscous than basalt.  Lava flowing from stratovolcanoes is generally up to 950 °C.  Because andesitic and felsic lava is quite viscous and sticky, it is more difficult for gas dissolved in the pooling magma to escape as it reaches the lower pressures at the earth’s crust and begins to cool.  As a result, rapidly expanding bubbles build up in the magma and extreme pressure builds up inside the magma chamber/ conduit/ pipe.  It is thought that the bubbles expand up to 1000 times their normal size as they pool in the magma chamber – the building pressure eventually causes the magma to explode (called a magmatic eruption), blasting it into tiny pieces of volcanic ash, and explodes the weakest point of the volcano off, usually at the summit – to allow gas, rising lava and ash to escape.  The resulting thick sticky lava flow from this kind of eruption usually creates steep sided volcanoes.  Felsic lava, being more viscous, produces a higher level of explosivity than andesite volcanoes and are much more dangerous to humans as a result.

The kinds of eruptions that occur at stratovolcanoes are varied – with more than one kind commonly occuring at the same volcano at subsequent eruptions or even through a series of continuous eruptions.  The kinds of eruptions are usually named after volcanoes where the pattern was first recorded – such as:

Strombolian Eruptions - Named after Stromboli, one of the stratovolcanoes making up the Aeolian island arc (as mentioned in the plate tectonic section).  Strombolian eruptions are generally low level mildly explosive reactions but generally involve the ejection of glowing cinders, lapilli (tephra) and lava bombs for tens of meters into the sky.  Cinder cones are normally produced at the vent of the volcano due to the style of eruption.  Cinders and lapilli (pyroclastic particles) predominate over volcanic ash.

Vulcanian Eruptions - Named after Vulcano, another Aeolian island arc stratovolcano.  This kind of eruption is much more dramatic and involves eruption of a dense cloud of ash-laden gas exploding from the crater and rising high above the peak – steaming ash commonly causes a whitish cloud near the upper level of the cone.  An extensive amount of pyroclastic rock is released from vulcanian eruptions in explosions described to sound like cannons being fired.  These eruptions are explosive because of the silicon-richer andesite magma.

Vesuvian/ Plinian Eruptions – Named after the famous stratovolcano, Mount Vesuvius, near Naples in Italy (famous for burying the town of Pompeii in 79AD).  Vesuvian eruptions are also called Plinian eruptions (from Pliny the younger/elder who described the 79AD eruptions) and are the most explosive and dangerous, with magma usually being of the highly viscous, silica rich, rhyolitic type.  Plinian eruptions involve massive explosions which send a  column of gas, pyroclastic fragments and ash high into the stratosphere to form a cauliflower-shaped cloud high above the volcano.
- In a “Vesuvian” eruption, as typified by the eruption of Mount Vesuvius in Italy in A.D. 79, great quantities of ash-laden gas are violently discharged to form cauliflower-shaped cloud high above the volcano.  Krakatoa near Java is another volcano which has had this kind of eruption in the past, along with Mt St Helens in Washington which erupted in 1980.   The explosions during plinian eruptions often create massive calderas - cauldron like volcanic features caused by the massive collapsing of land following emptying of the magma chamber.  The other feature of plinian eruptions is that they can often result in a massive reduction of size of a volcano because of the amount of summit exploded off the volcano during the eruption.  It is also common for this type of eruption to lead to deadly pyroclastic flows – A pyroclastic flow is a fast-moving current of extremely hot gas (which can reach temperatures of about 1,000 °C (1,830 °F)) and rock (tephra), which travel away from a volcano at speeds generally as great as 700 km/h.  The flows normally  hug the ground and travel downhill, or spread laterally under gravity.

 “The Eruption of Vesuvius as seen from Naples, October 1822″ from V. Day & Son,

Phreatic Eruptions –  Phreatic comes from the Greek phrear meaning well or spring – this is a type of eruption that tend to occur either on its own or preceding an alternate type of eruption – it is an eruption driven by explosive expanding steam from cold ground water, ice or surface water coming in contact with intensely hot volcanic rock or magma.  The distinguishing feature with this kind of explosions is that they only blast out fragments of pre-existing solid rock from the volcanic conduit – they do not erupt magma.  An enormous amount of steam, ash and rock – and often poisonous gas such as H2S are emitted in a large plume from the volcano and the explosion often leaves a large crater called a maar.  A maar is a massive low level crater that is characteristically filled with water. Phreatic activity can be quite violent – there were several phreatic eruptions at Mt St Helens in Washington before the major Plinian eruption in 1980.  Kilauea in Hawaii (my new favourite shield volcano) also commonly experiences phreatic eruptions.  It is thought that the eruption that obliterated Krakatoa in 1883 could well have been a phreatic eruption – it emitted the loudest noise ever recorded in history!!! ( info from U.S. Geological Survey http://www.usgs.gov/science/science.php?term=1209&type=feature)

Pelean Eruptions – In These are otherwise called glowing cloud eruptions and are similar to plinian eruptions in that they usually involve andesite or more silicon rich and viscous rhyolitic magma.  The distinguishing features are the glowing avalanche of hot volcanic ash/ significant pyroclastic flow that can move downhill up to 160km per hour and the formation of lava domes.  Lava domes are domes shaped mounds protruding from the crater of a volcano caused by very slow moving viscous lava – they are dynamic and can grow, shrink, erode and solidify.   Lava domes can be up to several hundred meters high and can grow quite quickly.  Lava domes can be particularly dangerous because they shatter during an eruption.  Mt St Helens in Washington has had a few pelean eruptions since the large plinian eruption in 1980.  Mt St Helens now has several domes which occasionally erupt – one of which slowly grew from 2004-2008 without eruption – it is now deemed to be stable.

Pelean eruptions have been known to occur with shield volcanoes too – notably they have been known to occur in Iceland, a region of diverging plate boundaries.

So… lots of different kinds of eruptions and it seems those at stratovolcanoes are typically much more dangerous than those at dome volcanoes.

The other thing mentioned in my research on stratovolcanic activity are lahars.  Lahars are mudflows which are composed of volcanic material/ tephra mixed with water- commonly from either heavy rainfall during an eruption (example – they have occurred when hurricane activity has occurred at the same time as a volcanic eruption) or from melted ice.   The mixture forms a cement like mud which is fluid when moving but solid when stationary and can bulldose anything in its path.  Lahars are commonly the main cause of death from volcanoes – they can flow quite quickly (up to 100km per hour) and can be massive – engulfing entire towns quite quickly.  A notable event occurred in Nevado del Ruiz, a stratovolcano in Columbia which erupted in 1985 to produce a lahar which killed 23,000 people and buried an entire town under 5 meters of mud.

Caldera Volcanoes:

Ok so this is an odd one!!! Some websites say these are the scariest most horrific of volcanoes and have the potential for mass devastation – that is because at some stage a stratovolcano has erupted to such extreme that it has part emptied the massive magma chamber and the volcano has caved in to leave a large caldera 1.6km + wide.  It seems that this type of volcano has been promoted as the life changing earth changing kind because if it exploded again with the same force it would have devastating effects similar to the original eruption that created it.   Some caldera volcanoes are designated as Supervolcanoes (possibly this may have come from a Discovery Chanel doco…). Caledra Volcanoes can occur on hot spots or converging plates.  The commonly used example of a supervolcano caldera is Lake Toba in Indonesia (on converging plates…) and the largest volcanic lake in the world.  Some paleontologists believe the volcano erupted around 75,000 years ago and it caused mass devastation - plunging the earth into a 10 year winter and wiping out all but around 5-10,000 humans.  in 1883, Krakatoa, an island/volcano in Indonesia not far from Lake Toba erupted with a massive explosion that obliterated 3/4 of the island and caused a tsunami that wiped out islands and killed 37,000 people.  Krakatoa is now a submarine (underwater) caldera but has a little volcano (Anak Krakatoa) growing from it at a rate of 6 meters per year).  Another commonly referenced caldera volcano is Yellowstone park in the USA – it is a massive caldera on a hot spot which has recently been moving slowly and has a history of erupting every 6000 years or so (and is just about due to do it again!!!).  Yellowstone is considered, at least by the discovery channel, to be the next most likely place for a supervolcanic eruption that could wipe us out, change the weather and cause mass destruction to the planet…  The lava from Caldera volcanoes is usually rhyolitic and cool at temperatures less than 800C.

I mentioned the amount of greenhouse gases that come from volcanoes previously – Caldera volcanoes have the potential to trigger significant widespread climate change due to the excessive amount of particulate matter, which can change weather patterns, and the excessive amount of greenhouse gas emitted from a mega eruption.  Extreme acid rain is another potential ecological hazard of super eruptions.

Now what have I missed out??? Many websites like the award winning How Volcanoes Work website http://www.geology.sdsu.edu/how_volcanoes_work/index.html also mention scoria cones, also called cinder cones, and mud volcanoes

Scoria volcanoes/ Scoria cones/ Cinder cones:

Scoria volcanoes are usually termed cinder cones or scoria cones rather than volcanoes.  They are the littlest of volcanoes – they are made up of basalt tephra piled into a cone.  They can occur on their own or are commonly found as parasitic cones on the side of other volcanoes.  Scoria cones occur as a result of strombolian eruptions which explode loads of basalt tephra into the sky which then settles back to form a tephra cone (as mentioned above).  They are distinct in that they have straight sides and large summit craters and are also distinguished by the fact they normally only ever erupt once (most, but not all, fit into this catagory.

Here is a scoria cone which is a parasitic cone on the Hawaiian shield volcano Mauna Kea

So last of all fumaroles….

Fumaroles:

These are not usually classified as volcanoes as such but are openings in the earth’s crust (a crack, fissure or hole), generally around or on volcanoes, where volcanic gases are erupted out.  As a result of the gases, fumaroles tend to emit clouds of steam and gas and are often covered in pretty yellow sulphur crystals from the large amount of sulphur gases emitted from most of them.   A fumarole can be considered to be just like a hot spring but where all the water has been converted to steam before it reaches the surface of the earth’s crust.

So hot springs…. a hot spring is a spring produced by the emergence of geothermically heated ground water.  They are not necessarily but are often found around volcanic areas and hot spots – they can also be man made.  In Australia there are geothermal hot springs in the Mornington Peninsula in Victoria.  Geothermal electricity involves a similar process to producing a geothermal hot spring – it involves tunneling deep into the earth’s crust and pumping down water to turn into steam- then using the steam to turn a turbine (like many other forms of electricity generation).

Geysers are a type of hot spring that involve ground water coming in content with magma which causes massive steam and water vents that spurt up into the sky.  Geysers are often taken over as electricity generating sites if they are consistent – otherwise they are turned into tourist sites since they are pretty spectacular.   Related to hotsprings and geysers are bubbling mud pools – this is similar to a hot spring but involves mud which has commonly been produced by mixing tephra from volcanic activity with water.

Rotorua on the north island of New Zealand is an amazing but incredibly stinky place I have been too… well worth a visit.  Rotarua is an area of extensive geothermal activity situated in a 22km caldera (now I know what that is!!!) – created by a major volcanic explosion 240,000 years ago that exploded enough tephra to completely cover 4000 square kilometers.  There are many lava domes inside the caldera and it is a place of excessive geothermal activity – containing hot springs, geysers, bubbling sulphury mud pools and fumaroles.  Rotarua looks amazing but it does stink of H2S and there are lots of areas of pretty yellow sulphurous rock around the place.   A couple of lovely piccies from Rotarua http://www.rotoruanz.com/resources/images/geothermal showing geothermal activity.

So the only questions I still have about volcanoes… why do people live near them? well I have a fair idea it is because of the nutrient and mineral rich soils generated as a result of volcanic activity.  They are also pretty places.

A good website I found http://www.geography-site.co.uk/pages/physical/earth/volcanoes/why%20people%20live%20near%20volcanoes.html goes through each of the reasons people live near volcanoes… and there are 500 million people living close to or on top of volcanoes… MINERALS… lots of minerals, come from the mantle during volcanic eruptions and volcanic rocks can be rich sources of all minerals including silver, gold, copper, lead and zinc… all valuable and are mined extensively.  GEOTHERMAL ENERGY…. a very cheap energy source to harness if you live near a volcano – in Iceland and New Zealand, geothermal energy is commonly harnessed to power their turbines and generate electricity.  FERTILE SOILS… usually a volcanic area has to have been around thousands of years before the rocks weather enough to make fertile soil – when this happens though the soil is extremely fertile.  The Darling Downs region in Queensland is an example of red fertile volcanic soil from a long extinct and eroded shield volcano.  TOURISM… odd I know to want to rock up to a volcano which may erupt at any time… or indeed is erupting… but they are fascination places and I have been to two of them myself so can vouch for that curiosity.  My dad had the same curiosity but nearly came undone by Bagana, a volcano in Bougainville, he and his pilot flew into it to take a look (out of curiosity) and less than 24 hours later it erupted (and has been pretty much erupting consistently since!!!).  Why people live near volcanoes is probably a discussion to have at the beginning of a class to get those brains connecting volcanoes to ecology…

So teaching details about volcanoes… I can see perhaps this being organised into a jigsaw activity in the explain phase, although I would do some hands on activities to familiarize students with where volcanoes occur, how many are active and an opportunity to see the “ring of fire” and see how volcanoes tend to occur in chains (Google Earth would be good for this)… and perhaps different types of lava? in the explore phase to provide students with some scaffolding prior to  - in the explore phase.

THE Volcanic Explosivity Index… (probably also for the explore phase, elaborating on the concept that different lava types cause different eruptions)

This is a measure of the explosivity of a volcanic eruption – it looks at ejecta volume and plume.

from Newhall, Christopher G.; Self, Steve (1982). “The volcanic explosivity index (VEI): An estimate of explosive magnitude for historical volcanism”. Journal of Geophysical Research 87 (C2): 1231–1238.

VEI Ejecta volume Classification Description Plume Frequency Example Occurrences in last 10,000 years*
0 < 10,000 m³ Hawaiian non-explosive < 100 m constant Kilauea many
1 > 10,000 m³ Hawaiian/Strombolian gentle 100–1000 m daily Stromboli many
2 > 1,000,000 m³ Strombolian/Vulcanian explosive 1–5 km weekly Galeras (1993) 3477*
3 > 10,000,000 m³ Vulcanian/Peléan severe 3–15 km yearly Cordón Caulle (1921) 868
4 > 0.1 km³ Peléan/Plinian cataclysmic 10–25 km ≥ 10 yrs Eyjafjallajökull (2010) 421
5 > 1 km³ Plinian paroxysmal > 25 km ≥ 50 yrs Mount St. Helens (1980) 166
6 > 10 km³ Plinian/Ultra-Plinian colossal > 25 km ≥ 100 yrs Krakatoa (1883) 51
7 > 100 km³ Plinian/Ultra-Plinian super-colossal > 25 km ≥ 1000 yrs Tambora (1815) 5 (+2 suspected)
8 > 1,000 km³ Ultra-Plinian mega-colossal > 25 km ≥ 10,000 yrs Taupo (26,500 BP) 0

http://www.ees1.lanl.gov/Wohletz/Erupt.htm

Australia’s volcanic history!!!! Yes I have mentioned volcanoes in Australia before – no volcano has erupted here for thousands  of years and all our volcanoes are considered to be extinct on the main land – there is a possible designated hotspot at Lord Howe island which has volcanic activity as well as a possible minor one just under Victoria.   Like much of the earth in the past, Australia had a good deal of volcanic activity.  Having never been located on a plate boundary, all of our volcanic activity has been “hot spot” volcanic activity and we have many remnants of shield volcanoes and cinder cones all over the country.  As well as the Romsey Australia site previously mentioned, I took a look at the fantastic resources on the Geoscience Australia website http://www.ga.gov.au/image_cache/GA10095.pdf which takes students through the geological history of Australia from the PANGEA days in the cambrian period on… including where major volcanic activity was occurring and what minerals were deposited in extensive amounts and what life was present in the region.  There are fantastic pictures of all of these extinct volcanic regions http://www.volcanolive.com/australia.html here…   An example of an extinct volcano familiar to all of us Gold Coasters is the Tweed Volcano formed 23 million years ago when this point of eastern Australia passed over a hot spot.  The Tweed volcano was an extensive shield volcano and has eroded extensively in the 23 million years leaving some impressive large remnants including Mount Warning, Lamington Plateau, Springbrook Plateaus and Tamborine mountain.  These features sit in a Caldera but the caldera wasn’t formed by a supervolcano – just an eroded extinct shield volcano.  The volcanic rocks we climb on and surf near at Burleigh heads are formed from the basalt lava flows from the Tweed volcano and the entire volcanic area is extremely fertile, supporting an extremely biodiverse range of plant and animal species and intermittent rain forest environments.  Also close to home are the Glasshouse Mountains – these are actually massive rhyolite plugs/ cores from eroded away volcanoes that were active 26 million years ago. 


As mentioned – I was thinking volcanic and earthquake activity in Australia would be good to do in the elaborate phase of a plate tectonics unit, so students can use their new knowledge to predict our volcano and earthquake activity.  

 I think maybe the super exciting volcanic eruptions (sorry… devastating but fascinating is perhaps a more appropriate way to describe them… ) could also be something well placed in the elaborate phase.  Once students understand eruption types and terminology they would be better placed in understanding why the events were so devastating.   

Photo of a volcano errupting.

I have always been fascinated about volcanoes, and have even been to a couple, so have been looking forward to this section!!!

First of all- Volcano – the term came from a little volcanic island in the Mediterranean off Sicily called “Vulcano” – Vulcano was thought, in roman times, to be the chimney of the forge of Vulcan- the Roman god of fire and blacksmith of the gods.  Hot lava, clouds and dust from Vulcano was thought to be from Vulcan beating out thunderbolts for Jupiter, king of gods, and weapons for Mars, the god of war…  from http://www.crystalinks.com/volcanomyth.html  :O)  I can see why the Romans would think that! Particularly if they had been drinking wine boiled in lead vats…

The modern day definitions of volcano/ volcanism, from Britannica concise encyclopedia:

volcano, Vent in the crust of the Earth from which molten rock, hot rock fragments, ash, gas, and steam issue.

volcanism, also spelled vulcanism, any of various processes and phenomena associated with the surficial discharge of molten rock, pyroclastic fragments, or hot water and steam, including volcanoes, geysers, and fumaroles.

So what the hec are pyroclastic fragments??? turns out it is the ash and rocky fragments resulting from the massive explosion from expanding gases during an eruption.  The more violent the eruption, the more pyroclastic fragments produced.  Pyroclastic fragments that have been airborn are also known as tephra – if the pyroclastic fragments are amalgamated into a larger form, they form pyroclastic rock.  Hydroclastic fragments are fragments produced through the explosion of lava as it hits water or ice.  The explosion is caused by the rapid cooling of the lava which allows the dissolved gases to escape quickly as the lava solidifies, causing it to shatter.

Lava is a term used to describe magma or molten rock as it erupts through a vent and after it is cooled and solidified.

hmmm I can see a word list or glossary is going to have to be written for or by students – maybe as part of a webquest.

I have looked at quite a few websites on volcanoes and have found TONNES of pretty pictures – very little that relate them to plate tectonics though, which is what we need to know….

http://www.geology.sdsu.edu/how_volcanoes_work/  seems to be the best site encountered thus far – with a bit of stuff on the U.S. Geological Survey website to back up the authenticity of their information!!!

The map above shows a picture of the earths plates – showing a clear representation of the offsets in the mid-ocean plate boundaries (i.e. the plate boundaries are neither uniform or straight).  The map also shows, with red dots, the positioning of the approx 550 active volcanoes of the world (although most of these are dormant and have been for many years…).  As you can see by this picture, almost all the terrestrial volcanic activity occurs along plate lines – the few that occur mid-plate are around designated “hot spots”.

In the section on plate tectonics there was a review of the 3 distinct plate boundary types

1. Divergent boundaries – plates move apart and new crust is formed

2. Convergent boundaries – plates come together crust is destroyed

3. Transform boundaries – plates slide past one another

(The USGS mention at this point that some plate boundaries are uncertain)

Volcanoes are abundant at both divergent and convergent plate boundaries – but not transform plate boundaries.  Spreading center volcanism occurs at divergent plate boundaries and subduction zone volcanism occurs at convergent plate boundaries.  Volcanic eruptions that occur mid plate are classified as intra-plate volcanism.

Here is a FANTASTIC picture from Encyclopedia Britannica that shows the three environments of volcanism from http://www.britannica.com/EBchecked/topic/632078/volcanism

The only potential problem I see with the picture is that it kind of looks as if the core is coming up through channels to the surface – it is not actually the molten core that is coming out… If it was – then the oceanic crust would be made from iron!!!

It is still an excellent picture and one well- worth showing if a better option does not come up.  So back to the info on the How Volcanoes work website… A very good website!!!

Spreading center volcanism:

Spreading center volcanism is the most productive volcanism and occurs mostly in oceans. Sea floor spreading, described in the Plate Tectonics section of this blog, is an example of spreading center volcanism.  Spreading center volcanism occurs at divergent plates which are pulled apart as a result of convection currents in the mantle.  As the plates pull apart a vent or “rift” is created between the plate boundaries and is filled with rising magma/lava (mix of molten rock, volatile compounds and solids) from the mantle/ asthenosphere.  The process of sea floor spreading is continuous, although different parts of the diverging fault may spread at different rates.  On average, sea floor spreading in the Atlantic ocean is increasing the ocean’s size by around 2cm per year.  Ridges form at divergent boundaries due to the continual release of lava.  Ridges are areas of built-up basalt/ crust that can be as large as a mountain – in-fact some of the largest mountain ranges in the world are actually underwater near divergent fault lines. As the crust is pulled apart at divergent plate boundaries, rifts can also develop away from the central vent/rift due to tension.  These rifts can spill magma and can also build up over time into decent sized underwater basalt mountains/volcano islands.  Generally with these rift volcanoes, basalt magma will pond just beneath the crust and every now and then a tap, jerk or knock from plate movement will allow the magma to surface as lava.  Spreading center eruptions are usually fissure eruptions (fissure volcanoes) – i.e. there is no exciting explosion – magma just pours out of the cracks/ rifts/ vents in the lithosphere and these rifts can be very small or up to a few kilometers long.  Underwater spreading center volcanism often produces bulbous shapes known as pillow basalt – the basalt-rich lava from volcanic activity is cooled rapidly in the deep water and sets into pillow shaped mounds.

Underwater spreading center volcanism produces thermal springs that allow heat stable bacteria to flourish – the life connection to underwater volcanoes is represented beautifully by David Attenborough in this video

Pillow Basalt from rift volcano

Iceland lies on the mid Atlantic ridge at the divergent boundary between the Eurasian  and North American plates.  Iceland is an example of an island built up as a result of spreading center volcanism.  Around 1/3 of Iceland is volcanically active and, being on top of a divergent plate boundary, it is growing in size every year.  Eventually, it is thought that Iceland will break in two as the ridge gets bigger and eventually allows the inflow of sea through the country.

The volcanoes associated with continental divergent plate boundaries are normally shield volcanoes – called this because they look like big shields rather than forming very tall mountainous volcanoes like the ones you see in movies (picture from Encyclopedia Britannica).  These shield volcanoes take their shape from the usually non-explosive slow lava flow.

A picture of a Shield volcano in Iceland

Subduction zone volcanism:

Unlike the usually quiet spreading center volcanism, Subduction zone volcanism produces more violent episodes.  The most active volcanic region on earth, the ring of fire, is laden with subduction zone volcanoes.  The ring of fire occurs at the converging boundaries of the Pacific Plate.

So as a refresher of convergent boundaries – this is when two plate boundaries are being forced together and one boundary usually gets pushed underneath the other – i.e. the lithosphere of one plate ends up subducting under the other.  In the ring of fire, the oceanic crust always subducts under continental crust or other oceanic crust (usually just near to continental crust), which leaves a massive oceanic trench.  Oceanic trenches resulting from convergent plate boundaries are the deepest points on earth and can be up to 11km deep (e.g. the Mariana trench).

As the subducting slab is pushed further under the ascending plate, it encounters higher pressures and more extreme temperatures.  The high water content of the descending oceanic crust, along with the high carbon dioxide content, actually serves to reduce the melting point of the various metals and minerals in the descending rocky lithosphere.  As the rocky lithosphere begins to melt it becomes less dense and rises. Eventually this magma makes its way to the surface and over years and eruptions can build up to form large volcanoes – usually occurring  in a linear belt parallel to the oceanic trench. When the convergent plate boundaries occur in the ocean the belt of volcanoes is known as an island arc and when the boundaries are at the edge of a continent it produces a terrestrial volcanic arc.

The Aleutian island chain is an example of an island arc – it consists of a chain of around 300 island volcanoes in the Pacific ocean (part of the ring of fire) just off the coast of Alaska.  An example of a volcanic arc are the Cascade volcanoes of the USA – these run up the coast from California through Oregon, Washington and British Columbia, and include the famous Mount St Helens volcano in Washington that had a severe eruption in 1980.

Island arc formed by oceanic-oceanic subduction  Volcanic arc formed by oceanic-continental subduction
 Island arc formed by
oceanic-oceanic subduction
 Volcanic arc formed by
oceanic-continental subduction

Volcanoes produced by subduction zone volcanism are usually stratovolcanoes and are made up of alternating layers of igneous rock (cooled solidified lava) and tephra (solid materials/ash emitted through eruption). The molten magma composite from the subducted lithosphere rises as it becomes more liquid/ less dense, and pools in a magma chamber under or within the stratovolcano. Because the pressure is relatively low in the chamber, the gasses dissolved in the magma are allowed to escape, causing a buildup of gases (including CO2, SO2, Cl2, H2O).  Magma and gas will build up to the point where the pressure behind the volcanic cone is too high and there will be a sudden and explosive eruption to blow of the cone and allow the escape of the gas, tephra and some lava.

Usually, stratovolcanoes do not involve as extensive lava flow as shield volcanoes.  Sometimes vents appear in the side of volcanoes due to weaknesses – these may serve to allow gas to escape but are also the origin of formation of parasitic cones which can also blow off during an eruption.

Here is a lovely diagram of a strata volcano  

The most famous volcanoes, including Vesuvius, are stratovolcanoes.

Intra-plate volcanism:  

It makes sense why you would have volcanic activity at plate boundaries – but how about Hawaii??? Hawaii is in the middle of the Pacific Ocean, far from any plate boundary.  The current most excepted theory is that the Hawaiian volcanoes, and several other intra-plate volcanoes, occur at “hot spots“.  Hot spots are sub-lithosphere intense plumes of magma that occur as part of convection currents.  As mentioned previously, convection currents occur because the magma in the mantle close to the earth’s core is extremely hot – as a result it is less viscous and dense than the cooler harder magma above it.  Magma from the mantle next to the core will rise as a result of the lower density, and the the more dense magma above it will sink toward the core due to gravity.  It is thought, in some areas, the plumes of intensely hot molten magma which have risen to the asthenosphere can be up to 300km in diameter (hence the term hot spot!!!).  The intense heat of the hot spot makes the lithosphere very fragile and prone to cracks/ vents.  As a vent opens up it causes an outpour of lava – and over time these outpours can build a volcanic island.   Hot spots stay in a constant location, while the lithosphere is pulled in a particular direction slowly as a result of tectonic plate activity.  As a result of this “continental drift” it is common to find a chain of volcanoes at a hot spot – with the youngest and most active volcano being directly over the hot spot and older inactive volcanoes, that used to lie over the hot spot, lying nearby.  An example of this is the Hawaiian-Emperor seamount chain (Hawaiian islands).   The main island of Hawaii is the newest and most volcanically active, as you move north west you will see progressively older extinct volcanic islands which used to lie over the hot spot (millions of years ago…).   A new submarine volcano is forming to the southeast of the main island of Hawaii – it is though that this will eventually become the main volcanic island while the Hawaiian “Big Island” volcanoes will become extinct.

This picture comes from the USGS (United States Geological Survey) website.

Shield volcanoes are the predominant type of volcano occurring at hots pots – they have a tendency not to produce explosive eruptions, although they occasionally will.  Hawaii is made up of 5 separate shield volcanoes, one of which, Kilauea, has been in a constant state of eruption since 1983, making it the most active volcano on earth.

The spots in red are considered to be major Hot Spots – the yellow and green spots are considered to be less significant hot spots – AND WOW!!! LOOOK WE ARE ON THE MAP!!! looks to be something going on in Victoria… I was thinking of doing earthquake and volcanic activity in Australia in the Elaborate phase of a unit so students could apply their knowledge about volcanoes and earthquakes to our country (make it more real for them!!!)- and we have our own hotspot!!! (all be it a mild one… must read more about that…)   Oooh oooh – have found a great website that talks about the history of volcanoes and earthquakes in oz – as well as what is sill active http://home.iprimus.com.au/foo7/volcmap.html.

The details of the volcanism types would probably best be covered in the explain section of a plate tectonics unit… Need to know a bit more about volcanoes though… have a few holes in my volcano knowledge…

This comes from the U.S. Geological Survey – a fantastic site!!! also likely to be a good reference point for accurate information since there seems to be a bit of uncertainty about some things (like when looking for a definition for plate tectonics I found a site that said plate tectonics is the process of sea floor spreading… think it should be more like sea floor spreading occurs due to plate tectonics maybe… )

from http://pubs.usgs.gov/gip/dynamic/historical.html#anchor9464740

In geologic terms, a plate is a large, rigid slab of solid rock. The word tectonics comes from the Greek root “to build.” Putting these two words together, we get the term plate tectonics, which refers to how the Earth’s surface is built of plates. The theory of plate tectonics states that the Earth’s outermost layer is fragmented into a dozen or more large and small plates that are moving relative to one another as they ride atop hotter, more mobile material.

When this text mentions outer layer, it is important to note that they are talking about the lithosphere rather than just the crust – when they say earth’s surface to me I think of the crust – no doubt middle years students would too if they have just learned about the egg thing.  

So the theory is the earth’s lithosphere is made up of plates that fit in or join together.  There are 7 main plates and 7 smaller plates (and some itty bitty ones we wont go into…) – most, aside from the pacific plate, contain some land and ocean.  The plates are sitting on top of the very hot semi-solid asthenosphere – a part of the earth’s mantle that lies directly underneath the lithosphere.  Because of the semi solid state of the asthenosphere, plates can move/ float slowly over its surface.   

Here-in lies another discrepancy in on-line info… the asthenospere has been described as anything from solid to liquid, depending on what source you read…

In looking for piccies of tectonic plates I came across loads of maps… but almost none of them had NZ in them, and if they did they didn’t have the plate boundaries lying over the top of the south island… and I KNOW they do lie over the south island.

Good old wikipedia has come good though

So the plates:

Main ones: Australian plate, Pacific plate, Antarctic plate (largest), African plate, South American plate, North American plate, Eurasian plate

Little ones: Nazca plate, Scotia plate, Indian plate, Caribbean plate, Arabian plate, Philippine plate, Juan de Fuca plate

Notable things for Australia – we sit smack bang in the middle of a plate (no lines running through us…) and NZ sits in the middle of the joins of the Australian plate and the Pacific plate – with the joins running through the middle of the south island.

Where the plates join we have “fault lines”.  These are the regions where the majority of earthquakes, volcanoes and growing mountains are, and they occur because of the way the plates edges interact with each other (more on this in a minute).

Tectonic plates are constantly in motion because of convection currents that occur within the mantle.  The convection current in the mantle is where extremely hot molten rock from the mantle sitting close to the core rises because it is less dense that the cooler more solid layers above (liquids are less dense than solids so they rise).  In return, the cooler denser semisolid mantle close to the lithosphere falls down to the core due to gravity (more dense things sink due to gravity…).  This heat cycling occurs on a constant basis.

Wow – I know about convection from physics!!! how clever… So… there is a possibility students have done global warming stuff or have talked about convection in other classes.  They would likely be familiar with the concept but may need help remembering and translating it to the mantle…

It would be good to look at a picture explaining convection currents… it is easy to pick up from this picture…

from http://www.ucmp.berkeley.edu/education/dynamic/session1/sess1_earthcurrents.html

So the plates, as you can see by the upper layer in the picture (denoting the lithosphere), get pulled a little across the surface of the earth depending on the direction of the convection currents.  Plates get pulled an average of 2-10cm per year and this is why continents are moving.

Because the convection current causes movement in different directions, plate edges interact with each other.  There are 3 ways the plates may interact with each other – by being squished together, by being pulled away from each other, or by being pushed sideways across each other.  This causes boundaries that are CONVERGENT (pushed together), DIVERGENT (pulled apart) or TRANSFORM (pushed sideways).

Convergent boundaries (Con comes from a Latin word meaning together.  Think about Convergence Collides) – these are also called destructive boundaries.

At convergent boundaries the plates literally collide with each other – this can be a bit destructive so this is also sometimes called a destructive boundary.  If you think about pushing two sheets of paper together quickly what happens? usually you will have some push up on one side and then one layer will slip underneath the other – this is also what happens with plates so makes sense… I think a visual representation would certainly be needed to establish that in some student brains…

picture from http://www.plate-tectonics.org/plate-tectonics/types-of-plate-boundaries.html

The denser plate of the two coming together is pushed under the other in a process called SUBDUCTION.  Active volcanoes often arise in subduction zones.
The 3 common scenarios  of convergent boundaries:
1. Oceanic plate meets oceanic plate – the denser plate is subducted resulting in a deep sea trench.  There is one of these off the coast of Japan – where the eurasian plate meets the pacific plate –  movement with this plate is the cause of most of japans earthquakes and tsunamis.  The trench is shown by the dark region next to this map of Japan (from http://godzilla.wikia.com/wiki/Japan_Trench).
Japan as actually at the junction of 3 plates – the Eurasian plate, Philippine plate and the Pacific plate.

2. Oceanic plate meets continental plate – the oceanic plate boundary subducts under the continental plate boundary and the edge of the plate is lost into the molten mantle.

3. Continental plate meats continental plate – in this case the denser of the two plates subducts under the less dense plate and mountains are often formed at the boundary of the top plate.  An example of two continental plates converging is in the Himalayas – caused by convergence of the Indian plate and the Eurasian plate.  As the Indian plate is pushing into the Eurasian plate the Himalayas are growing in size by up to 1 cm every year!!

Divergent boundaries

At divergent boundaries the plates are being dragged away from each other – this causes cracks in the lithosphere which are then closed up by molten rock from the mantle to form new crust.  Divergent boundaries mainly occur in oceanic ridges but can occur on land – an example is this divergent fault in Iceland

from http://www.sciencephoto.com/images/download_lo_res.html?id=693650090

because new crust is created at divergent faults, this type of fault will make a continent or ocean slowly grow in size (unlike convergent boundaries which tend to involve loss of crust so make continents shrink).  Divergent faults in oceans cause the formation of giant ridges which act as spreading zones – where sea floor spreading occurs.  Sea floor spreading is thought to be the cause of continental drift. (but in thinking about this more logically… it is actually the convection current that is ultimately responsible for continental drift… 

http://www.wwnorton.com/college/geo/animations/sea_floor_spreading.htm

this is a cool animation to help visualise how sea floor spreading causes continental drift

Transform boundaries

Transform plate boundaries occur where two plates slide past one another.  Unlike convergent and divergent boundaries, crust is not created or destroyed.  Most transform boundaries occur in the ocean and are formed as a result of offsets in mid-ocean ridges.  Here are two pictures that explain this from http://users.indigo.net.au/don/nonsense/transoffsets.html - basically the plate boundaries do not occur in smooth straight lines – they have offsets – so when you have divergent activity and sea floor spreading from ridges, you will have transform boundaries occurring along the plate boundaries).


http://www.iris.edu/hq/programs/education_and_outreach/animations/2 is an animation to describe this.

Transform faults also occur through some continents – the most familiar to us is the one that runs through the south island of New Zealand.  There are also a transform fault running through California http://geology.com/plate-tectonics.shtml has an interactive map that shows all the major faults and what kind they are.

Transform faults are areas of earthquake activity – the great amount of friction bought about by the rocks in the lithosphere causes a resistance in transverse movement.  Despite the convection currents pushing the transform faults, they will catch and quite often will not move immediately.  When the pressure builds up to a high enough level the transformation will occur, the crust at the boundaries will slide and the sudden release in energy will trigger an earthquake.  Transform activity has been responsible for major earthquakes in Christchurch and San Fransisco.   New Zealand, and many other places, have a mixture of transform and convergent boundaries.  A picture of one of these faults can be seen here – from http://www.sciencelearn.org.nz/Contexts/Earthquakes/Sci-Media/Images/Ostler-Fault-Mackenzie-Basinalong with the result of one of the transform slips!!!


Google Earth file http://bbs.keyhole.com/ubb/ubbthreads.php?ubb=download&Number=138517&filename=286222-PB2002.kmz  OMG GOOGLE EARTH has all of the faults on the 3D globe showing a different colour line for boundary types!!!  Google Earth would have to be a FANTASTIC teaching aid in this section.  I think the info about the plate boundary types needs demonstrations – or at least the animation clips I have listed – Think this would be hands-on stuff best suited to the Explore phase… 

The Earth is of course a planet… and we kind of know what it looks like on the outside – and I remember seeing pictures from my school days of what it looks like on the inside – a core… a crust… and stuff in-between… now what was inbetween…

The following review is derived from http://www.earthscrust.org/science/historic/andrija.html combined with Science Basics 04 Year 10 by Joanne Macown (2008) Nelson Cengage Learning, and USGS Inside the Earth – found at http://pubs.usgs.gov/gip/dynamic/inside.html

Here we go!!!

Well firstly – obviously with a planet, the further into it you go the hotter it is going to be and the higher the pressure.  The earth is made up of 3 main parts a bit like an egg – the core (yolk), the mantle (white) and the crust (shell).

The inner core is made up of iron and nickel(about 2600km thick) – despite being well above the melting temperature of iron and nickel at around 5000C, the inner core is solid because of the great amount of pressure that exists in the center of the planet.  The solid inner core is surrounded by a liquid outer core around 2500km thick – this is made from molten iron and nickel.

As the earth rotates the molten metal spins and this is thought to be responsible for the earths magnetic field.

Picture USGS Inside the Earth http://pubs.usgs.gov/gip/dynamic/inside.html

The mantle is the middle layer of the earth – it is a 2,900km dense layer of mostly semi-solid rock organised into sublayers – the very outer most sublayer of the mantle, just underneath the earths crust, is quite solid and rocky and is divided into distinct plates - this layer, along with the earth’s crust, is often referred to as the Lithosphere (from Greek Lithos = stone).  The plates sit directly on top of another mantle sublayer called the asthenosphere (Greek asthenos = weak).  The asthenosphere is a thinnish layer of semi sold hot-molten rock.  Scientists believe the rigid lithosphere “floats” slowly over the top of the asthenosphere.

The earth’s crust is the outermost and thinnest layer – it is ridged but brittle in comparison to the other layers – and is prone to cracking.    Beneath the oceans, the crust is about 5km thick and beneath the continents it averages about 30km thick – this of course varies a bit – under some mountain ranges it can be 100km thick.

The Moho or Mohorovicic discontinuity is the boundary between the crust and the upper mantle – it has distinct seismic activity so is thought to be made from a different rock composition to the crust.

This is interesting and like a refresher course… I did have trouble in this section when compiling information about lengths of different layers –  i.e. some have the core being smaller than 2,500km and others have it being larger… It is worth considering that there is some discrepancy there if students have 2 different reference points for this information.  There are also many sites that state the mantle is solid rigid rock… but of course the mantle would have to have fluid properties (even semisolid rock has fluid properties) to fit into the rest of plate tectonic theory… So… need to make sure students are pointed to references which are consistent with this fluid model if they are provided with any references or resources for their learning.  

Again… I think this refresher on the earth is probably best included in the engage session 

I think it makes something more memorable when you know where something came from, so I thought I would look up the history of plate tectonics – which I find has been around for a surprisingly short time!!!

I read a few writings on tectonic history at http://www.ucmp.berkeley.edu/history/wegener.html from the University of California Museum of Paleontology, http://pangaea.org/wegener.htm SciLinks from NSTA and http://scign.jpl.nasa.gov/learn/plate2.htm, the Southern California Integrated GPS education module.  The whole idea of plate tectonics had its origins in 1912 with a German scientist, Alfred Wegener, who noticed that if all the pieces of the earth were jigsaw pieces they would kind of fit in together perfectly.  He actually wasn’t the first to notice this – some explorers had noticed the Africa looked as if it could fit into South America and there had been a paper written some 300+ years ago that suggested it – but Wegener was the first to propose they had been stuck together, were still moving apart and postulated a mechanism as to why they were moving apart.

Everyone at the time thought Wegener was pretty silly but he did have some evidence to back up his claims.  Palaeontologists, digging up fossils, had found similar remains on the coasts of two continents that Wegener had predicted were once joined together, but were now separated by many thousands of kilometers (previously paleontologists had said the continents must have been linked by bridges).  Wegener went further by developing his “Continental Drift” theory.

Wegener’s Continental Drift theory, although inaccurate, paved the way for the modern theory of plate tectonics. Wegener suggested that the continents had, in the past, all been joined together into a giant super-continent – which was later labelled as Pangea (Ancient Greek for Entire Earth) and that continents were moving away from each other toward the equator due to centafugal force from the earths rotation.  He also hypothesized that as the continents move they encounter resistance from the crust in-front of them.  The resistance causes areas of the continent to compress and fold upwards forming mountains near the continents edges.  Wegener also suggested that India had drifted north into Asia forming the Himalayas and Mount Everest.

Wegener’s theory that continental drift caused mountains was reasonable to many followers – the alternative theory for why there were mountains was called called the “Contraction” theory.  The Contraction Theory was that the planet was once a molten ball and, in the process of cooling, the surface contracted folded back over itself to form mountains.  The big hole with this theory is that if it were right then you would expect all mountains to be the same age – and this was known not to be true.  The Continental Drift theory was not without it’s problems – it was known the centrifugal force exerted on the continents would be far too low to cause them to move, but Wegener and some of his close supporters continued plugging away at the theory of continental drift and eventually alternative mechanisms were proposed (Weneger’s involvement eventually came to a tragic end in 1930 when he froze to death in Greenland).   Two of the most notable advocates of Wegener’s theory of continental drift were an English Geologist, Arthur Holmes, who came up with the idea of convection cells, and Harry Hess, a US geologist, who developed the sea-floor spreading concept.   Both of these geologists died in the 60′s – at the beginning of the wider spread acceptance of tectonic plate theory.  Up until the mid 60s most scientists poopood the whole continent moving thing…

Eventually ridges under the sea were mapped and were found to be connected to sea floor spreading – and were also found to be connected to mountain patterns on land.  The connection of the ocean ridges to mountains led to the idea that it was plates that were moving rather than continents and that plates were made up of the earths crust (containing both land and sea), and were slotted together at the ridges to totally cover the planet.  The 1950s and 60s also saw the collection of evidence for Holmes’ convection cell sea floor spreading concept (still haven’t found out what that is yet…) through the development and installation of sonar equipment set up for war purposes.  At this time there was also a comprehensive collection of seismology data – from readers set up to measure nuclear testing!!! and this data that made the significant link between these “ridges” , earthquakes and volcanic activity.   Gosh could you just imagine the look on the geologists face when they stumbled across that!!! that would most certainly be an OMG moment…

The actual “tectonic plate theory” that is understood today, was written in full in papers submitted 1965-1967.  It is now largely accepted in its current form by most geologists.

Further evidence to support tectonics is being gathered all the time.  One of the significant technological advances which has allowed accurate mapping of tectonic movement is the development of GPS technology… the info from our little devices in the car actually comes from a satellite.  NASA GPS monitoring satellites give indications of how much continents move during earthquakes (eg – they say Japan moved 2 meters!!!)

hmm so this is all really interesting… but is it a good idea to talk about what the past theories actually were – I think not… just incase students remember “centrifugal force and earths rotation” rather than the fact it was not an accurate mechanism…

Perhaps summarizing this to mention Wegener was the first to develop a theory of why continents were drifting apart, and even though his mechanism was not accurate, he did pave the way for other geologists to come up with a viable mechanism.   Actually – this could be done as an example of scientific method at work.  The other thing to note – because it is an essential learning from memory (shall look it up) – is that advances in technology have been part of the reason for the development of the theory of plate tectonics – seismic readers, marine geology equipment, satellite imaging, GPS…  This info would best be suited to an engage phase in the first lesson.

So before delving into what tectonic plate theory is… I thought I would look up to see where Australia fits into this continental drift thing… I can see us squished into the right hand side of the Pangea map above…

The current proposed time line is that 200 million years ago the continents were joined together as a giant landmass – Pangaea – surrounded by a large Ocean – Panthalassa.  (before this, apparently the continents were separated and moved together into the Pangaea formation.

150 – 200 million years ago, Pangaea broke into two super continents – Laurasia (forming a northern hemisphere continent) and Gondwanaland (forming a southern hemisphere continent).

These two supercontinents have broken into smaller continents which have drifted to their current positions – the Laurasian continent breaking into North America, Europe and Asia and Gondwanaland breaking into South America, Africa, India, Antarctica, Australia and New Zealand.

About 65 million years ago, Australia and Antarctica were still narrowly connected and shared the same cool temperate rainforest.  About 50 million years ago, Australia separated from Antarctica and headed north at a rate of around 8 cm per year.  Along with heading north came increased temperature, mountain building and isolation.  We have been our own continent for 50 million years and this has led to the evolution of unique native flora and fauna which is not seen anywhere else in the world.   The continents of the world continue drifting at an average rate of around 2.5-5cm per year – we can see this now more clearly through accurate measurements from GPS satellites – Australia is drifting 35degrees east of North at a rate of around 6.7cm per year.

This comes from Geoscience Australia’s website http://www.ga.gov.au/image_cache/GA10096.pdf (or more accurately, one of their teaching resource posters)

It would also be interesting for students to see this in the engage phase… Perhaps the poster link could be printed for students too – since it shows the different ages on a time scale

Next step… I think I need a refresher on the earth before tackling tectonic plate theory…

Step number one in my mission to learn about geology/earthquakes/ plate tectonics was to look at the National and State curriculum documents to give me some direction and boundaries in my quest for knowledge and understanding.

The National Curriculum has the majority of coverage about this area in their Year 9 Earth and space sciences curriculum

Science / Year 9 / Science Understanding / Earth and space sciences

Content description

The theory of plate tectonics explains global patterns of geological activity and continental movement

Elaborations

  • recognising the major plates on a world map
  • modelling sea-floor spreading
  • relating the occurrence of earthquakes and volcanic activity to constructive and destructive plate boundaries
  • considering the role of heat energy and convection currents in the movement of tectonic plates
  • relating the extreme age and stability of a large part of the Australian continent to its plate tectonic history

Code ACSSU180

The Queensland State curriculum also has the majority of its plate tectonic earthquake stuff in Year 9

Science/ Year 9/ Knowledge and Understanding/ Earth and Beyond

Geological evidence can be interpreted to provide information about past and present eventse.g. the earth’s surface is shaped by volcanoes and earthquakes, which can be understood in terms of the theory of plate tectonics.

The Queensland state curriculum description looks less scary than the National Curriculum… destructive plate boundaries is not something I have ever heard of before… So the 5 steps above are going to shape my learning direction – and after I am confident I know about them, then I will look at related curriculum in year 9 which would provide curriculum links and what is covered in the way of plate tectonics before and after year 9.

Because I am a keen believer and follower of the constructivism, I thought I would see if I had any alternate conceptions about plate tectonics.

I found an on-line quiz  about plate tectonics on the soft  school website  http://www.softschools.com/quizzes/science/plate_tectonics/quiz415.html

1. The observation that the continents fit together like puzzle pieces, and may once have been connected, led Alfred Wegener to propose a theory in 1910 called

A: continental plowing

B: continental drift

C: wandering continents

D: shape matching of continents

2. The essence of Wegener’s idea was sound, based on some scientific observations. Which of the following supported his theory?

A: Matching fossil plant remains found on two different continents

B: Matching reptile remains found on two different continents

C: nearly identical sedimentary rock types of same age in widely separated locations

D: all of the above

3. The development of submarine warfare druing World War II created a pressing need to map the ocean floor. This actually led to research on the ocean floor that would help explain the movement of the continents. What tool was used to do this mapping?

A: underwater cameras

B: sonar surveys

C: studies of living things

D: rock sampling

4. Scientists found that the continents were moving apart from each other due to magma rising out of mid-ocean ridges, and they called this

A: sea floor spreading

B: sea floor rising

C: changing sea floor

D: underwater volcanos

5. The Earth’s continents were once connected in one giant continent called

A: Eurasia

B: Indo-Australia

C: Pangaea

D: Pacifica

6. The Earth’s crust is divided into 7 major plates, which include all of the continents. Along which two plates do we see major earthquake activity?

A: Pacific and North/South American

B: Pacific and Eurasian/Indian

C: South American and African

D: A and B both

7. Wegener’s old theory, called sea floor spreading, was found too simplistic because it did not explain how the continents would move. It was replaced by a theory called

A: plate tectonics

B: crustal forces

C: paleomagnetism

D: weather forces

8. Plate tectonics is our current theory of how the movement of continental masses relates to the movement of ocean basins. This movement explains many phenomena, such as

A: earthquakes

B: volcanoes

C: weather patterns

D: all of the above

9. Plate margins are places where much activity occurs. Earthquakes occur, for example, along convergent margins, where plates are

A: moving apart

B: sliding past each other

C: colliding

10. Volcanoes occur in similar locations to earthquakes, and are common along plate boundaries. Sixty percent of volcanoes occur surrounding the Pacific Ocean, a location called

A: “the hot zone”

B: “the Ring of Fire”

C: “the Volcano Zone”

11. Plate tectonics can also be the direct cause of forming

A: lakes

B: streams

C: mountains

D: oceans

12. Plate tectonics, or the movement of pieces of Earth’s crust, is thought to be caused by

A: volcanoes

B: earthquakes

C: convection currents in Earth’s mantle

D: hot spots

Theme :               Plate Tectonics Science Quizzes                              Result: 8/12       

Number               Actual   Your Answer(s)

Review – 1           B             B

Review – 2           D             C

Review – 3           B             B

Review – 4           A             A

Review – 5           C             D

Review – 6           D             B

Review – 7           A             A

Review – 8           D             D

Review – 9           C             B

Review – 10         B             B

Review – 11         C             C

Review – 12         C             C

hmmm… 8/12 is not great – particularly since I guessed half the ones I got right…. I will take the quiz again after I have learned something I think!!!

My next plan… what is plate tectonics exactly… and what are the major plates…


I am embarking on a new mission!!!

I am determined to learn about fault lines, tectonic plate movements, “the ring of fire” and all other geological phenomena that has, so far, been evasive throughout my extensive science education!!!  My mission has been catalyzed by an assignment requiring the gathering information and teaching techniques relating to “the middle school science topic I know the least about”.   Geology is, by a long way, the science topic I know least about. Keep glued to this blog for updates…

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