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Plate Tectonics 38 For many years it was believed by geologists that the location of the continents was fixed. These scientists believed that the locations of the continents were determined many billions of years ago. It was believed that the continents were simply areas where the crust was too high for the oceans to cover them over. Modern scientific discoveries have helped us understand that this view of the Earth is inaccurate. We have learned that the lithosphere (the crust and upper layer of the mantle) float on top of the asthenosphere and can move around. How does this happen? At the bottom of the ocean, located almost exactly halfway between the continents are under-water mountain ranges. This is where hot magma escapes from the Earth’s core, and spreads outward. As the seafloor spreads outward, the continents are carried across the sea, riding on top of the crust. As new crust is created it forms what resemble giant plates. One side of the plate is where new crust is being made, while the other side is where older crust is being destroyed. These plates are called tectonic plates and move from 5-10 cm a year. Materials: colored pencils, Plate Boundary Map What To Do: 1. Don’t glue in the map. 2. Find all the arrows on the map (10) and color them orange. 3. Find the Nazca Plate and lightly color it blue. 4. Find the South American Plate and color the continent green and the ocean blue. 5. Find the mid-Atlantic Ridge with the help of your teacher and trace it in red. 6. Color the ocean on either side of the mid-Atlantic Ridge blue. 39 40 41 The Effects of Moving Plates The earth’s crust is broken up into many pieces called plates. These plates move along the top of the asthenosphere. The plates move very slowly-at rates of several centimeters a year. The cracks between the plates are called plate boundaries. Along plate boundaries the plates slide past each other, pull apart or move together. The Theory of Plate Tectonics explains all of this movement. Plate tectonics is what causes major crustal features such as mountains, volcanoes, fault lines and ocean basins. When the plates move toward each other the land crumbles and form high mountain ranges. The Himalayan Mountains were formed with the IndoAustralian plate slammed into the Eurasian plate. When plates pull apart ocean basins are formed such as the Atlantic Ocean. Volcanoes and earthquakes also occur around many plate boundaries. Watch the Plate Tectonics segment of TLC Elementary School: Geological Processes from www.discoveryeducation.com Questions: 1. What was Pangea? _____________________ 2. What two continents fit together like a puzzle? ________________________________________ 3. What did Alfred Wegner call his theory? ___________________________________________ 4. What theory do scientists use to explain the moving continents? _________________________________ 41 Your teacher will show you a Power Point called Types of Plate Boundaries. Questions: 1. How do convergent boundaries move? _________________ 2. How do transform boundaries move? __________________ 3. How do divergent boundaries? _______________________ 4. What type of Plate Boundary is shown? ______________________ 5. What type of effects does this type of boundary have on the area around it? _______________________ _______________________ 6. What type of Plate Boundary is shown? ______________________ 7. What type of effects does this type of boundary have on the area around it? _______________________ _______________________ 8. What type of Plate Boundary is shown? ______________________ 9. What type of effects does this type of boundary have on the area around it? _______________________ _______________________ Name ____________________ 42 Period _____ EXIT TICKET Plate Tectonics 1. Convergent plate boundaries cause what type of crustal feature? A. Ocean basins B. Mountains C. River Valleys 2. Divergent plate boundaries cause what type of crustal feature? A. Ocean basins B. Mountains C. River Valleys 3. Transform plate boundaries cause what type of crustal feature? A. Ocean basins B. Volcanoes C. Glaciers 4. The only place you can see the Mid-Atlantic Ridge on land is A. The Himalayan Mountains B. The Andes Mountains C. Iceland 5. The theory that explains all the movement along plate boundaries is called – A. Big Bang Theory B. Conservation of Mass Theory C. Theory of Plate Tectonics Name ____________________ Period _____ EXIT TICKET Plate Tectonics 1. The only place you can see the Mid-Atlantic Ridge on land is A. The Himalayan Mountains B. The Andes Mountains C. Iceland 2. The theory that explains all the movement along plate boundaries is called – A. Big Bang Theory B. Conservation of Mass Theory C. Theory of Plate Tectonics 3. Convergent plate boundaries cause what type of crustal feature? A. Ocean basins B. Mountains C. River Valleys 4. Divergent plate boundaries cause what type of crustal feature? A. Ocean basins B. Mountains C. River Valleys 5. Transform plate boundaries cause what type of crustal feature? A. Ocean basins B. Volcanoes C. Glaciers 42