Continental Drift & Plate Tectonics

Continental Drift Theory First proposed by Alfred Wegener in 1912: 250 million years ago, all of the continents were combined into one super-continent called “Pangaea” The continents gradually drifted apart to where they are today Wegner didn’t make up this theory out of the blue – like all scientists, he based it on evidence

Evidence Summary Geographic fit of South America and Africa Fossils match across oceans Rock types and structures match across oceans

Geographic Fit Continents look like they could be part of a giant jigsaw puzzle Here’s how they moved apart

Fossils Match Plant and animal fossils found on the coastlines of different continents

Fossil Fuel in Antarctica Tropical plant remains (coal deposits) found in Antarctica this is evidence that Antarctica was once much warmer and much closer to the equator, since tropical plants don’t grow in Antarctica today

Rock Structures Match Across Oceans Same rock patterns found in South America, India, Africa, Antarctica and Australia

Rock Structures Match Across Oceans

Alfred Wegener German meteorologist and geophysicist Developed Theory of Continental Drift Used 3 pieces of evidence Early 1900s

The theory that states that parts of Earth’s crust drift/float on top of the liquid mantle (convection currents).

PANGAEA -Gigantic super- Continent that existed over 200 million years ago. -Means “ALL EARTH”

Evidence -Continents fit together Like puzzle pieces -Same fossils were Found where pieces fit Together -Similar landforms found On each continent

Europe North America Asia Africa South America Australia Antarctica

8. Juan De Fuca Eurasian North American Arabian 10. Cocos 11. Caribbean Philipine African Pacific South American 15. Caroline Indo-australian Nazca Scotia Antarctic

Divergent “Dividing” Transform “Sliding” Convergent “Colliding” Forms mountains Indo-Australian plate collides with Eurasian plate to form Himalayan Mountains. Divergent “Dividing” On land, forms rift valleys In ocean, forms sea floor spreading “Mid-Atlantic Ridge” Causes earthquakes San Andres Fault Transform “Sliding”