text: Rain water percolated down through the upper layers of the Earth's crust until it hits bedrock. Normally, it collects there and gradually move downhill into the nearest aquifer.\n\nIf the bedrock is being heated by underlying areas of magma, the pressure builds up and the water finds its way to the surface, where it is released as hot springs, hot mineral pools or geysers. Yellowstone Park is the largest of these areas in the United States. However, there are literally hundreds of areas that have hot springs.