A geyser is jet of boiling water and steam issuing from the earth in a few volcanic regions. The jet of water may persist from a few moments to an hour or more. Beneath the geyser, there is some hot rock and a narrow fissure connects the rock to the mouth of the geyser. Water reaches the rock through this fissure where it is heated to about 100 degree Celsius. Now the steam pressure inside, forces the hot water to come out to the surface of the earth. The flow of hot water continues till such time as cold water does not return to the fissure. The cold water is again converted into steam and as the pressure rises, the hot water is thrown out.
The jet of hot water may rise in the air to a height of 100 meters or more. In some cases it rises to only 1 or 1.5 meters. Geysers are known to exist only in Iceland. New Zealand and Yellowstone national park in the USA. Of these three, Yellowstone has by far the most impressive display of geysers. These geysers are a delightful sight for the viewers and are popular tourist spots.
A Hot Spring in IcelandThe temperature of water of a hot spring is higher than that of ordinary springs. According to scientific findings, ground water temperature rises with increasing depth. The rate of increase in generally about 1 degree centigrade for each 25 meter of increase in depth. When underground hot water flows out regularly through some crack or fissure, it is called a hot spring. In some volcanic regions, the steam formed by the heat of the molten rocks is forced out in the form of hot water.
Many minerals get dissolved in hot spring water. The hot spring water containing dissolved sulphur is good for skin diseases. The water of some springs is very hot.
The Maoris of New Zealand cook their food in the local hot spring water. In Haryana, a place called Sona has a hot spring which is quite famous and Manali also has a number of hot springs. Among the hot springs in Dehradun, the capital of the newly formed state of Uttaranchal, the Tapt Kund is a hot water sulphur spring which is quite famous throughout India. Reference: Children’s Science Library by A.H.Hashmi.