CONTINENTAL DRIFTMs. Kopchick’s Earth Science Class

The earth is a dynamic Planet.

• Its surface is constantly changing along with the interior earth. As convection currents move in the mantle, earthquakes occur, volcanoes erupt, mountains are uplifted and sea basins are opened.

Continental Drift

•Hypothesis that continents are mobile.•First argued by Alfred Wegener in 1915.•Wegener published a 1915 book “TheOrigins of Oceans and Continents”

Evidence of Continental Drift

• Puzzle piece fit of the continents • The present shorelines seem to fit together as

a puzzle• A much closer fit is using the edge of the

continental shelf

Puzzle piece fit

Glacial Evidence• Glacial till was left behind in Africa and India• Currently these areas are to warm to have

glaciers• Evidence of a cooler earth? No, plenty of

tropical plants at the same time.• Explanation: Africa and India were once closer

to the Poles

These areas were once closer to the South Pole

Paleoclimatic Evidence

• As Africa and India were near the southern part of Pangea, North America, Europe and North Africa were near the Equator.

• Topical reefs and corals along with coal deposits can be found in Alaska today.

• Since these things can only survive in warm climates, the explanation is that Alaska was once closer to the Equator.

Fossil Evidence

• Mesosaurus – Estuarine reptile Only from S. America & S. Africa• Glossopteris - Heavy seeds, subpolar climate Found in India, Australia, S. America & Africa Heavy seeds in a subpolar climate• These creatures could NOT have traversed an

ocean.

Structural Continuity

• Correlation of rocks and fossils on both sides of the Atlantic Ocean.

Fish fossils on top of Mt. Everest ??

• Fossils of marine life found at mountaintops in the Himalayas can only be explained by crustal uplift.

Hot Spots or Mantle Plumes

• Stationary areas in the mantle that eject magma to form volcanoes and the continental plate or oceanic plate moves the volcanoes with them like a conveyor belt.

Oceanic Crust moving the volcanoes away from the hotspot