Plate Tectonic and Continental Drift

History of Continental Drift Alfred Wegener proposed the Theory of Continental Drift in

1910 CONTINENTAL DRIFT: The continents are drifting on top of the

ocean floors. They once were together in a massive continent called Pangaea.

Proof 1. Continents fit together like a puzzle on the map. Proof 2. Fossils of plants and animals located where they can not

exist. Proof 3. Exactly same rock identified on two different continents. Proof 4. Evidence of glaciers in deserts and deserts in Alaska

Evidence against this theory 1. No evidence of scarring on the seafloor and no remnants of debris. 2. Wegener could not explain the mechanism of movement.

Pangaea

Harry Hesse

Hess a geologist studied the MAR during WWII looking for submarine. He helped prove that the sea floor was spreading in the Atlantic ocean. He was also the first head of NASA.

Harry Hess Discoveries Plates move on the asthenosphere Asthenosphere is an elastic layer between the hard crust and

the molten mantle. In the Mid Atlantic Ridge (MAR) the earths crust is spreading

and is known as a DIVERGENT BOUNDARY In the Himalayan and Andes mountains, the plates are

colliding and building mountains which is known as CONVERGENT BOUNDARY

When an ocean plate is forced under a Continental Plate, SUBDUCTION occurs, causing Volcanoes. This is common in Italy and Washington State and is known as a Subduction Convergent Boundary

Boundary Types

Draw and label these

Divergent Boundaries-Pulling away from each other.

Mid Atlantic Ridge = (MAR)is a divergent boundary.

Convergent Collision Boundary

Himilaya Mtns – where indo-australian plates hits asia plate.

Subduction zones

San Juan de Fuca Plate – the subduction zone that creates U.S. Volcanoes, in washington state.

Transform boundaries – side by side collisions-create faults and earth quakes.