In order for geysers to exist, there first must
be a source of heat. Scientists theorize that molten rock, or
magma, rises in convection cells like water boiling in a pot.
The left side of the illustration on this page shows the traditional
view of a hotspot as a plume of magma rising from earth's core.
The right side shows another theory that the Yellowstone hotspot
originates at a much shallower depth. Select Yellowstone's Hotspot
to learn more.