Geysers - Old Faithful Virtual Visitor Center

A geyser's eruption is a chain reaction that follows a specific order of events. Launch an

interactive feature that explains the eruption process.

A tall column of steam and water rise from Steamboat Geyser

Superheated water rises through the underground plumbing system.

Pressure from overlying rock and water prevents most of the water in the system from boiling, although steam begins to form and expand.

Geysers often have constrictions in their natural plumbing system, usually near the surface. The steam bubbles, being too large and numerous to pass through a tight spot, become trapped behind such a constriction.

The temperature and pressure within the system increase. The trapped bubbles move about violently—so violently that some of the underlying water is lifted above the bubbles and shoved through the constriction.

This causes an instant decrease in pressure and much of the water within the system flashes into steam. The steam takes up so much space that the remaining water is forcefully thrown from the geyser’s vent and an eruption begins. The eruption stops when the water reservoir is depleted or when the system cools.