A geyser is the result of underground water under the combined conditions of high temperatures and increased pressure the surface of the earth. Since temperature rises approximately 10F for every sixty feet under the earth’s surface, and pressure increases with depth, water that seeps down in cracks and fissures until reaches very hot rocks in the earth’s interior becomes heated to a temperature in excess of 2900F. Because of the greater pressure, it shoots out of the surface in the form of steam and hot water. The result is a geyser.

In order to function, than, a geyser must have a source of heat, a reservoir where water can be stored until the temperature rises to an unstable point, an opening through which of the hot water and steam can escape, and underground channels for resupplying water after an eruption.

Favorable conditions for geyser exist in regions of geologically recent volcanic activity, especially in areas of more than average precipitation.

For the most part, geysers are located in three regions of the world: New Zealand, Iceland, and the Yellowstone National Park area of the United State. The most famous geyser in the world is old faithful in Yellowstone Park. Old Faithful erupts almost every hour, rising to a height of 125 to 170 feet and expelling more than ten thousand gallons during each eruption.