Plate tectonics and continental drift

Front

What is the theory of continental drift?

Back

The theory that continents have moved over geological time and were once joined together in a single landmass.

Front

What observation did Alfred Wegener make that led him to develop the theory of continental drift?

Back

Continents appear to have once fit together.

Front

What is ridge push?

Back

A tectonic process where elevated mid-ocean ridges push tectonic plates away from the ridge.

Front

What is the process of sea-floor spreading?

Back

The formation of new oceanic crust through the upwelling of magma at mid-ocean ridges.

Front

What are deep-oceanic trenches?

Back

Narrow, deep depressions in the ocean floor formed by the subduction of one tectonic plate beneath another.

Front

What is subduction?

Back

The process where one tectonic plate moves under another and sinks into the mantle.

Front

What are convection currents?

Back

The movement of fluid caused by differences in temperature and density, driving plate tectonics.

Front

What is the difference between oceanic and continental crust?

Back

Oceanic crust is denser and thinner than continental crust, which is thicker and less dense.

Front

What are transform boundaries?

Back

Places where tectonic plates slide past each other, causing earthquakes.

Front

What is the significance of magnetic stripes on the ocean floor?

Back

They provide evidence for sea-floor spreading and the history of Earth's magnetic field reversals.