1. Plate Tectonics

2. Earth’s Interior

3. lithosphere Earth ’ s thinnest layer Earth ’ s thinnest layer divided into about 30 huge, moving divided into about 30 huge, moving masses of rock, called plates masses of rock, called plates plates move about as fast as fingernails grow, and have been for billions of years

4. plates are made of solid rock, mostly basalt, and are about 7 km to 100 km thick some plates carry granite continents on them like rafts - granite is less dense than basalt, so it actually floats brittle upper lithosphere is often called the crust the formation of the Earth ’ s major geographic features can be explained by Plate Tectonic theory

5. 50 years before Plate Tectonic theory, there was a theory called Continental Drift continents move in different directions, a few cm/year proposed by Alfred Wegener in 1912 continents were once joined in a supercontinent called Pangaea

7. Mountain Ranges ancient mountain ranges end at the edge of one continent, and mountains of same age and type start again on the “ matching ” continent overseas ex: Appalachians in U.S. are similar in age to mountains in Scotland and Scandinavia

8. Rock Layers each rock layer is caused by a change in the environment some examples... - volcanoes make ash or basalt layers - river deltas make sandstone layers - glaciers make till layers - swamps make coal layers - still water makes shale layers complex sequences of ancient sedimentary layers match up on now-distant continents more recent layers on different continents do not match up