Continental Drift Integrated Science

What is it? Continental Drift is the idea that the continents are slowly moving over the Earth’s surface It also includes the idea that all continents were once joined together in one large land mass called Pangea.

Who came up with it? Alfred Wegener Proposed it in the early 1900’s, but everyone thought he was crazy. People started to believe it could be correct in the 1960’s.

What evidence is there to support it? Fossil Evidence Mesosaurus fossils on only the South American and African coast. Ferns that grew in connected areas on Pangea Rock Formations Similar rock formations present on South American and African Coasts Mountain Chains would connect if continents were one large land mass.

Continental Drift Explains other Findings. Evidence of ice sheets have been found near the equator. When ice sheets were formed, the land was not at the equator.

How do the continents drift? Wegener couldn’t explain this. Now we can… New land is made at mid ocean ridges. Magma from the mantle rises at the ridge. The magma is cooled and it becomes part of the crust. This pushes land away from the mid ocean ridge and moves the continents too.

Most Famous Ridge Actually a long mountain range Found in the early 1900’s Actually understood what it is in the 1950’s

Mid Atlantic Ridge Cuts through Iceland. Mountains so high they poke above the ocean surface to make islands Bermuda

Where does the land go? Land is made at mid ocean ridges Land is destroyed at oceanic trenches At trenches one tectonic plate slides underneath the surface of another plate. The hot temperature melts the lithosphere (crust) and it becomes part of the magma.

Most Famous Trench Mariana Trench Near Japan Deepest trench in the world 36,000 feet deep and very hot. Very unusual animals live there!

How Do Continents Drift? The ridges provide a source of new land and a force to push the tectonic plates apart. The movement of the plates causes the continents to move. Over time, this caused Pangea to break up and the continents to move to their current locations.