>>41903988‘Water issuing from a hot spring is heated geothermally, that is, with heat produced from the Earth's mantle. In general, the temperature of rocks within the earth increases with depth. The rate of temperature increase with depth is known as the geothermal gradient. If water percolates deeply enough into the crust, it will be heated as it comes into contact with hot rocks. The water from hot springs in non-volcanic areas is heated in this manner.’
https://en.m.wikipedia.org/wiki/Hot_springEducate yourself. Even fucking Wikipedia knows more than you, not to mention the many other sources of info like your high school fucking geography book.
