Lobby > Exhibits > Why Geysers Erupt > Underlying Geology > Structure of the Earth

The Earth’s lithosphere (crust and upper mantle) is divided into constantly moving plates. Most scientific evidence supports the theory that the plate movement is caused by convection currents in the lower mantle where the temperature is greater than in the mantle’s upper sections. The hottest layers rise, forcing the cooler layers to sink. When those layers become hotter in turn, they trade places again. These convection currents cause the plates to slowly move about like crackers on a bowl of boiling soup. One plate may slide past or override another, or rising volcanic material may push the plates apart at mid-ocean ridges.

This interactive animation demonstrates how plates are thought to have moved over millions of years.

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