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Week 31 - Continental Drift, Plate Tectonics and Mountain Building

Exercise 3.1


Lesson 3.1: Continental Drift



ACTIVITY A: Walking on Egg Shells

Required Readings

Science in Action 7
pages 392 to 394
or

Science Focus 7

pages 383 to 385



Well ... not quite egg shells but a shell of sorts. Get yourself a hard-boiled egg; crack the shell on the outside. Very slowly, move the pieces of egg around on the surface of the egg.




In some places the egg white is exposed and in other places, where the pieces of shells bump together they buckle or overlap. This is somewhat similar to the surface of the Earth.




The surface of the Earth is like the cracked eggshell. The pieces (called plates) are slowly moving around. Where they spread apart, molten rock is exposed and where the plates collide they buckle or they overlap.




The shell of the Earth's shell (or crust) is broken into about 18 pieces. These pieces move around colliding into one another. When they collide parts of the crust is thrust upward (like the eggshell) and mountains are created. The movement of the Earth's crust also causes earthquakes and volcanoes.


ACTIVITY B: History of Continental Drift

Required Readings

Science in Action 7
pages 392 to 394
or

Science Focus 7

pages 383 to 385

Close your eyes and imagine that all the continents of Earth are attached together to form one landmass. What would a map look like? If you look carefully at a map, do you notice how well South America and Africa fit together? Alfred Wenger noticed. He studied the shape of the continents and then collected evidence from a variety of different sources and developed the Theory of Continental Drift.

Originally all the continents formed one super continent called "Pangaea." Follow this link to watch a video about Pangaea.

http://www.odsn.de/odsn/services/paleomap/animation.html

Look at the maps at this site to see how the map has changed gradually.

pubs.usgs.gov/publications/text/historical.html

 




PROOF OF PANGAEA

Read your textbook and then scroll down to read about evidence of Pangaea.


FOSSIL EVIDENCE



    The Fossil Record is Proof of Pangea

ROCK EVIDENCE




    Rock Evidence of Pangea

Almost all fossils are found in sedimentary rock. Sedimentary rock is formed when layers of sand gravel mud (soil) and plants are compressed into rock. Sedimentary rock forms layers or strata. These layers of rock are very distinctive for any given area. In order to understand Earth's history, we need to place geological events in their correct order. Geologists have discovered that the geological structures of the rocks in South West Africa and South East Brazil were distinctively identical, and the age of the rocks at these two areas was the same. This distinctive rock strata shared by the two land masses suggests that these two areas were once joined together.


Coal can be found underneath the cold and dry Antarctic ice cap and here in Alberta. We know that coal can only be formed in warm and wet conditions. This could mean that Antarctica and North America were once together with the other continents as part of Pangaea, and was once in a warm and humid region. Coal was formed before the continents drifted drifted apart. Antarctica became covered with ice and snow and the jungle ecosystem in Alberta transitioned to seasonal woods and grassland. That is why the coal can be found buried under areas that don't seem right for coal formation.


      ROCK STRATA


    COAL DISTRIBUTION
GLACIER EVIDENCE



    Evidence from Glaciation

      Glaciation in South America, Africa, India, and Australia is best explained if these continents were once connected. Glaciers covered all or part of each of these continents during the same time period in the geologic past.

    If the continents were in their present position, a major glaciation event that covered nearly all of the continents and extended north of the equator would be required. Geologists have found no evidence of glacial action in the northern hemisphere during this time period. In fact, during this time period, the climate in North America was warm.



    Wegener proposed that the continents were adjacent to each other during the glacial event. Therefore, glaciers spread over a much smaller area in the southern hemisphere and probably did not influence the climate of the northern hemisphere.

Exercise 3.1: Fossil Evidence