WHY DO THE EARTH'S CRUSTS MOVE?
The plates that make up the earths crust are constantly moving at around 2cm-3cm per year. The plates float on the magma beneath them. The process of plates being dragged in different directions is this:
- Heat from the core causes the mantle to heat up at the base
- Hot rock rises towards the crust
- As it rises, it moves away from the heat source at the base and cools down
- As it rises it is forced sideways
- It continues to cool and sinks back to the core
- As it reaches the core, it heats up again and rises again and cools down and falls etc.
SUMMARY: Convection curents move the tectonic plates on the earths surface. This process takes place inside the mantle.
Plumes-The convection cells where heat moves towards the surface are called plumes.Plumes bring magma to the surface and if it breaks down at the crust it will erupt as lava in a volcano. Some plumes are like long sheets of heat which form along constructive plate boundaries such as the North Atlantic Ridge, other plumes are like columns of heat which form hot spots.Hawaii is in the middle of a tectonic plate&has hot spots so there are volcanic eruptions.