Physical Geography

1. Physical Geography Continental Drift and Plate Tectonics

2. Key Terms • Erosion: break down of rocks into sediments followed by the movement of the sediments. • Faulting: movement of the land along a crack in the earth’s crust.

3. Key Terms • Folding: bending of rock layers. • Glaciers: slow moving mass of ice. http://en.wikipedia.org/wiki/File:Franz_Josef_glacier.JPG http://www.geolsoc.org.uk/gsl/education/rockcycle/page3801.html

4. Key Terms • Igneous rock: rock formed from the cooling of magma or lava (also called volcanic rock). • Metamorphic rock: rock formed when sedimentary or igneous rock is put under great heat and pressure.

5. Key Terms • Sedimentary rock: rock formed in layers from the compression of sediments over millions of years. • Plate tectonics: the earth’s crust is made up of thin (50 - 100 km) plates which are always in motion.

6. Introduction • Imagine that it is springtime and you are crossing a frozen lake. As you start to cross, the ice seems firm and solid but it is not. Before you reach the other shore, the ice starts to break up. Large cracks develop, separating the ice into huge plates. These plates are pushed by the wind, and currents in the water below. Some of these ice plates are pulled apart. Others are smashed together. Some of the plates drift away to form floating platforms.

7. CTVNews.ca Date: Fri. Mar. 9 2012 11:19 PM ET A large rescue effort was launched Friday afternoon to save a group of 27 ice fishermen who were marooned on a disintegrating ice floe on Ontario's Lake Simcoe. Read more: http://www.ctv.ca/CTVNews/TopStories/20120309/ice-fishermen-stuck-lake-simcoe-120309/#ixzz1qPred6ym

8. What does this have to do with geology? The earth's surface is like the frozen lake. It is a thin layer of solid rock (plates) moving on top of a layer of material that is flowing. Every year there are about 30 000 earthquakes that are strong enough to be felt. These earthquakes show where the earth’s upper layer is moving. Seismologists (scientists who study earthquakes) have discovered that earthquakes happen more often in certain places (see map below). Earthquakes and volcanoes occur mostly where the edges of the earth's plates are colliding or moving away from one another.

9. Earthquakes 1990 - 2005

10. Plate Tectonics • If you examine a map of the world, you might notice that the shapes of South America and Africa look like they could fit together. If they were once joined together, why are they now apart? What powers could move such large land masses? http://odt.org/hdp/

11. In 1915 the German scientist Alfred Wegener said that the answer was continental drift. He said that 300 million years ago all of the continents collided to form one supercontinent. He called the supercontinent Pangaea, which means "all-land". About 200 million years ago Pangaea started to break up. The pieces have since drifted to their modern positions.

12. What was probably the first evidence that Wegener had to prove that the continents were moving across the earth’s surface?

13. Jigsaw Puzzle Fit Probably the first clue that Wegener noticed to prove that the continents were once joined together was the close fit between Africa and the South America. Studies show that the fit between the continents is in the range of 95%.

14. What other proofs did Wegener have that the continents of the earth could move?

15. Fossil Animals and Plants Wegener found fossils that were identical but scattered over different continents. He thought it was impossible for these life forms to evolve identically in all these places. Instead, he said this is proof that the continents were once all joined together.

16. Geologic Proof The Appalachian Mountains in North America and the Caledonian Mountains in Scotland are of the same age, made of the same rock type, and have the same appearance. Wegener said this meant that they were the same mountain range, but had been split apart by the Atlantic Ocean in the last 200 million years.

17. Ancient Glaciers Wegener saw traces of glaciers in tropical areas (including South America, Africa, India, and Australia). To him this meant that all of these regions had been very close to the south pole in the past. Since then they had drifted to their warm locations.

18. Most scientists disagreed with Wegener because he could not explain what force was powerful enough to move continents. Finally, in the 1960s sonar technology helped to prove Wegener's theory. Canadian, J. Tuzo Wilson, helped to restart interest in the theory of continental drift. • By 1968 a new theory, called plate tectonics, was developed. http://gge.unb.ca/News/1996/1996.html

19. Plate tectonics helps explain most geologic actions. The theory says that the earth has a shell made up of about twenty plates. The plates are moving on top of a layer of very hot rock. This layer of hot rock is hundreds of kilometres below the earth's surface and flows like slow-moving plastic. No one completely understands what causes the plates to move over this weak layer. Some think it is the unequal distribution of heat in the core of the earth that causes convection currents to move the plates.

20. Plate Tectonics 6 – Rift Zone 5 – Subduction Zone 3 – Convection Current 1- Earth’s core 2 – The mantle 4 – Earth’s crust

21. 5 – Subduction Zones http://www.scienceclarified.com/landforms/Faults-to-Mountains/Mountain.html http://www.pbase.com/image/23431347 http://www.pedalandseaadventures.com/canadian-rockies-bike-tours.html

22. 6- Rift Zones http://all-geo.org/highlyallochthonous/2008/06/earthquake-in-iceland/ http://ffden-2.phys.uaf.edu/212_spring2005.web.dir/philip_fitzgerald/eruption.htm

23. The movement of the earth's plates has shaped Canada in many ways. The mountain on Canada’s east and west coasts were formed when plates bumped together. Plate tectonics have also been important in forming Canada's large deposits of oil, gas, and coal. These deposits were formed when Canada was located in a warmer, tropical climate. Where will Canada drift to in the next few hundred million years? Only time will tell.