Geysers are fountains of hot water and superheated steam that may spout up to a height of 150 feet from the earth beneath. The phenomena are associated with a thermal or volcanic region in which the water below is being heated beyond boiling-point. The jet of water is usually emitted with an explosion, and is often triggered off by gases seeping out of the heated rocks. Almost all the world's geysers are confined to three major areas: Iceland, the Rotorua district of North Island, New Zealand and Yellowstone Park of U.S.A. The world's best known geyser is perhaps 'Old Faithful' in Yellowstone National park, Wyoming which erupts at regular intervals- every 63 minutes on the average.