Sridhar D Iyer and Ankeeta Amonkar

When groundwater is heated by shallow-seated magma bodies, as in active volcanic areas, or if the water penetrates through cracks in the rocks and gets heated geothermally, the hot water that results and flows on the earth’s surface is called a “hot spring,” “geothermal spring” or “hydrothermal spring.” The water is warm to hot in contrast to the usually cold and cool springs and those at ambient temperatures. The hot water flows as small seeps, streams, forming a pond or a lake, and even flows as a river! The 6.4 km long Shanay-Timpishka River, a tributary of the Amazon River in Peru, South America, is the only boiling river in the world with temperatures between 45°C and 100°C. In India, hot springs are diverted into ponds called “kund,” where people immerse themselves and check if eggs and rice get cooked!

Geothermal heat is largely derived from the decay of radioactive elements that are present in the earth’s mantle. It is estimated that 45% to 90% of the heat that escapes from the earth is because of radioactive decay. The other source of heat is in areas of active volcanoes…read more on NOPR