What Causes Geysers?
A geyser is a vent in Earth’s surface that periodically ejects a column of hot water and steam. A geyser is caused by boiling water and escaping steam. In a few places in the surface of the Earth, there are tube like cracks that reach down to the hot rock inside. Water collects in these tubes and is heated by the hot rock.
The pressure of the water in the tube prevents the water from boiling until the temperature is far above the water’s usual boiling point. At last, the super-heated water explodes into steam, shooting steam and water high into the air. After the eruption, water refills the geyser hole, in advance of the next eruption.
Even a small geyser is an amazing phenomenon; however some geysers have eruptions that blast thousands of gallons of boiling hot water up to a few hundred feet in the air. Old Faithful is the world’s best known geyser. It is located in Yellowstone National Park (USA). Old Faithful erupts every 60 to 90 minutes and blasts a few thousand gallons of boiling hot water between 100 and 200 feet into the air.
Old Faithful is Getting Slower. Research done at the United States Geological Survey suggests that long-term drought conditions in the Yellowstone area have lengthened the time interval between Old Faithful’s eruptions. The delay is thought to be caused by a smaller water supply. Worldwide there are only about 1000 geysers and most of those are located in Yellowstone National Park (USA).