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Several men sit in and near a mud bath at Hot Springs, Montana, ca. 1900. Wood poles have been lashed together to make a frame and some canvas or burlap sheets have been tied to parts of it. Courtesy of the University of Montana-Mansfield Library via Big Sky Country Digital Network.

Hot Springs

Hot springs are geothermally heated groundwater found in locations all over the earth. A hot spring occurs when the water is heated above body temperature and brought to the surface. The temperature of the water is attributed to how far into the crust the water travels and is heated by hot rocks. In active volcanic zones such as Yellowstone National Park, water may be heated by coming into contact with magma. The high temperatures of magma cause the water to boil or become superheated. Hot springs in volcanic areas are often at or near boiling point and are dangerous to swimmers.

Warm springs occur when hot and cold springs mix outside of volcanic areas. Because heated water can hold more dissolved solids, warm and hot springs often have a very high mineral content. Because of folklore and claimed medical value, hot springs are popular tourist destinations and locations for clinics. Some hot springs have resort areas attached to them to offer services to visitors. Bathing in hot springs is thought to help lower blood pressure, improve sleep and joint mobility, and eliminate toxins from the body.