Chapter: Hotspots

Hawaii Islands

These facts brought the scientists to the conclusion that the source of the magma doesn't move. The islands on the other hand move with the Pacific plate about 4 inches per year. As you have already learned in the chapter about plate tectonics the convection currents in the asthenosphere are the cause of this movement. That's why the magma from the hotspots can't come from the asthenosphere. Otherwise there should only be one island which kept becoming bigger.

Consequently the magma has to come from an earth layer which doesn't move, i.e. from the outer core. The conveyor channels in which the magma is transported are called mantle plumes. You would have to imagine these plumes to convey magma only once or twice a year, which is geologically spoken quite frequently.

Graphic for a better understanding of the depicted processes. Sorry for the German explanations, this will be changed as soon as possible.

Now I have a very astonishing information for you! Which is the highest mountain of the earth? Sure, Mount Everest. Wrong! If you measure from the seabed, the highest mountain stands on Hawaii and is called Mauna Kea. This no longer active volcano is, believe it or not, 9700m high, but measured from sea level it only reaches 4206m.