Lesson 1 Earth's Moving Surface

The theory of plate tectonics states that Earth's surface is broken into large, rigid pieces that move with respect to each other.

These plates move slowly and can form volcanoes and mountains and cause earthquakes.

Plates move so slowly, it wasn't until the 1970s that scientists and engineers developed a way to measure their movement.

The movement of the continents is measured by the Global Positioning System (GPS), which uses satellites to track moving objects.

Even though the movement of the plates is slow, the changes are dramatic. About 200 million years ago, all of the continents were together in a super continent called Pangea. As the plates separated, the Atlantic Ocean was formed.

Convection occurs in the Earth's asthenosphere, just below the lithosphere causes plates to move.

Convection is the circulation within fluids caused by differences in density and thermal energy.

When subduction happens, this also allows for plate movement ans the colder, more dense plate moves below another plate.