What is the source of natural energy of the hot springs at Manikaran in Himachal Pradesh?

Geothermal energy is the heat energy produced within Earth's surface. Sometimes magma from inside come near to Earth surface heating up the rocks at shallow depth. The rocks instead heat the water body which comes in their contact. Similar tendencies prevail in Himachal Pradesh. Here, hot spring is situated near Parbati river spreading to a distance of 1.3 km.