NGS Plate Tectonic Sec 3: Continental Drift & Seafloor Spreading

What did Alfred Wegner hypothesize about the continents?

• They were once joined together in a single landmass.

• They were always separate.

• They were created by meteor impacts.

• They were formed by volcanic activity.

What was the name of the single landmass proposed by Wegner?

• Pangea

• Gondwana

• Atlantis

• Laurasia

What evidence did Wegner use to support his hypothesis?

• Similar languages spoken across continents

• Identical weather patterns

• Same ocean currents

• Matching mountain ranges and coal fields

Which scientist proposed the idea of seafloor spreading?

• Albert Einstein

• Alfred Wegner

• Isaac Newton

• Henry Hess

What is seafloor spreading?

• The formation of new continents

• The movement of tectonic plates

• The shrinking of the ocean floor

• The creation and destruction of the ocean floor

What forms along a mid-ocean ridge during seafloor spreading?

• Mountain ranges

• Volcanic islands

• New ocean crust

• Deep trenches

What type of rocks provide evidence for seafloor spreading?

• Pillow-shaped rocks

• Igneous rocks

• Sedimentary rocks

• Metamorphic rocks

What do magnetic stripes on the ocean floor indicate?

• Reversals of Earth's magnetic field

• The direction of ocean currents

• The presence of iron deposits

• The age of the ocean floor

What happens to the ocean floor at deep-ocean trenches?

• It turns into a forest

• It becomes a desert

• It sinks back into the mantle

• It rises to form mountains

What is subduction?

• The melting of glaciers

• The formation of new land

• The sinking of the ocean floor into the mantle

• The rising of ocean water