Convection Currents What causes the tectonic plates to move? The magma in the mantle layer is moving because of convection currents. Magma near the HOT core becomes less dense and RISES toward the cool crust. Magma near the crust COOLS, becomes more dense and SINKS back toward the core. The pieces of crust are pushed and pulled by the moving magma below.

1. Continental Drift Theory: Tectonic plates are constantly moving 1. Continental Drift Theory: Tectonic plates are constantly moving . At one time all the continents were all connected or close together.

Evidence #1 Some of the continents seemed to fit together like puzzle pieces. The coastlines of South America and Africa are a good example.

Evidence #2 Fossils of the same animals and plants that were the same time period, were found on multiple continents.

Evidence #3 Rocks from the mountains on coastlines of N Evidence #3 Rocks from the mountains on coastlines of N. America, Greenland, Europe and Africa matched in type of rock and age.

The supercontinent Pangea was formed 250 million years ago.

Mid Atlantic Ridge: A crack in the floor of the Atlantic Ocean that stretches from the North to the South Pole. It proved tectonic plates are moving and the Continental Drift Theory was correct.

Sea Floor Spreading: Lava spills out of the crack at the Mid Atlantic Ridge. The lava cools and creates brand new crust. The new crust forces the old crust to move away from the crack and pushes the ocean floor and the continents away from each other. Two of the continents that are pushed in opposite directions away from each other are North America and Europe/Asia.