What is a hotspot?

A hotspot is a small area within the mantle which is of a higher temperature than the area surrounding it, and is usually associated with volcanic activity.

Formation:

1. A vertical column of magma rises up the mantle (it is lighter than the surrounding rock) – this is called a magma plume

2. The magma plume pierces through the crust and heats the plate, erupting onto the ocean floor

3. A mound of solid magma is left and countless eruptions cause it to build up above sea level, forming a volcano

4. As the plate moves over the stationary hotspot, the volcanoes are moved away, cutting off the magma source and causing them to become extinct

5. New volcanoes are formed in the part of the crust that is now above the hotspot, creating a series of volcanoes

6. This results in a volcanic island arc

7. The older volcanoes are smaller due to erosion and weathering, whereas the newer ones are bigger

Example: Hawaii is made up of an island arc