Heat from the molten rock of the earth's interior is transmitted up through the solid rock of the earth's crust. Ground water circulating through these rocks becomes heated and follows cracks and fissures upward. Where the hot water can escape at the ground surface, a hot spring is formed.

Hot water is a better solvent than cooler water; it dissolves large amounts of silica, the major element of these volcanic rocks. That turns the area white. It looks like snow from a distance but it's really a rough sand.