2. Alfred Wegener German geologist 100 years ago Noticed the continents looked like a jigsaw puzzle He thought millions of years ago Earth’s continents were joined together
3. Continental Drift Theory http://www.eduplace.com/kids/socsci/ca/books/bkf3/imaps/AC_01_005_drift/AC_01_005_drift.html
4. Evidence for Continental Drift Mountains on east coast of South America are the same rocks as mountains on west coast of Africa Rocks are the same age
5. Evidence for Continental Drift Fossils were found of a freshwater reptile Mesosauras have been found in old rocks in South America and Africa That animal couldn’t swim across the ocean, so the land must have been connected
6. Evidence- ocean floor spreading The ocean between South America and Africa spreads 4 centimeters every year. This matches the Continental Drift Theory- 130 million years X 4 cm = 520,000,000 cm This is the width of the South Atlantic Ocean
7. Plate Tectonics When Wegener thought of his theory, he didn’t understand how the Earth’s crust could move around. Earth’s continents sit on plates of solid rock The asthenosphere (almost melted rock) acts as a slippery surface the plates move around on
8. Plate Tectonics- Ocean spreading Magma pushes up and forms new land Causes tension (push/pull) on plate Push causes the ocean floor apart and separates plates on either side of the mid-ocean ridge
9. Plate Tectonics- mountain building Fold mountains Compression = squeeze/pushing together Example: Himalayan mountains
10. Plate Tectonics- mountain building Fault-block mountains One plate rubs past each other causes a shear (force that twists, tears, pushes past each other) Example: Grand Teton Mountain Range
