Plate Tectonic Theory Evidence TEK 8.9A
Main Concept Why are there so many Earthquakes near us? TEK 8.9A - Describe the historical development of evidence that supports plate tectonic theory. Why are there so many Earthquakes near us?
Brain Break
Notes Two main people are responsible for the theory Alfred Wegner Started working on his theory in the early 1900’s German Harry Hess Started his theory in the 1960’s Worked for the US Navy
Notes Continued Alfred Wegner’s Theory Called the ‘continental drift hypothesis’ First proposed the idea of Pangaea Stated that it about took 200 million years to get to the current location Idea came from the fact that all of the continents fit together like puzzle pieces Actually took the idea from Abraham Ortelius
Notes Continued Concepts supporting Wegener Puzzle like fit of continents Matching sedimentary rock layers Layers of rock on the east of the US matches rock layers on the west coast of Africa Matching ranges of fossils Like the sedimentary layers, fossils matched on different continents
Notes Continued Glacial remains in tropical areas Showed the either that continents moved or glaciers were able to exist in hot, moist areas Tropical plants fossils found in arctic areas Same as above, how did they survive if the continent did not move.
Notes Continued Harry Hess’ Theory Seafloor Spreading Hypothesis New crust was added on the ocean floor pushing the older crust out Pushes North/South America away from Europe/Africa but pushed North America closer Russia on the other side Still supported Wegener but provided proof
Notes Continued Concepts supporting Hess Scientist measured the age of rock layers and found that rocks in the middle of the Atlantic Ocean were much younger than on the coasts
Notes Continued Magnetic striping When rock cools the magnetic crystals point north and south North and south move occasionally and there are organized bands of crystals pointing different ways.
Plate Tectonics Theory Merged the two theories into one. The crust, lithosphere, is broken into nine major plates There are many smaller plates Different types of faults make new crust and can also return the crust to the asthenosphere, or molten core. Next week we study the fault types.