Annually, there is more than a half meter rain and snow in Yellowstone. The water sinks into the porous soil. The high temperature of the magma heated the water, and that searches in the form of a geyser, a hot spring, a mudpot or a steamhole another way out. Under the ground in Yellowstone is a large channels and tubing. Depending on this system is the form determines how the heated water comes to the surface.