Hydrothermal features located throughout Yellowstone provide a visual reminder that the powerful volcanic forces which shaped this unique land are still very active today. Snow melt and rain water permeate below the earth's surface, where it is superheated by an immense magma reservoir, which at places is located only a couple miles beneath the earth’s crust. The water, reaching temperatures above 400ºF, then makes the journey back to the surface, resulting in geysers, hot springs, and thermal runoff.