hot spring

A hot spring is a concentrated discharge of groundwater to the surface. Unlike springs in general, the emergence of hot springs, also known as thermal springs, is enhanced by the pressure created from the heat of warm rocks within the Earth. Thus, such springs are most common in tectonically active regions. The temperature at which a spring becomes “hot” is an anthropomorphic ninety-eight degrees Fahrenheit. Hot springs are relatively common in the Americas. They may contain mineral properties thought to be beneficial to health, and in some locations their waters are contained and deployed as spas. In 1804, President Jefferson sent William Dunbar and George Hunter to explore what would become the Hot Springs Reservation in Arkansas (the oldest area in the National Park system). Dunbar reported that “the temperature of their waters is from 130 to 150˚ of Farheneits’ [sic] thermometer. . . . I found by the aid of an excellent microscope, both Vegetable and animal life, the first a species of moss, the latter a testaceous bivalve of the size of the minutest grain of Sand.” Of his mid-nineteenth-century sojourn in the region of the Yellowstone River, Osborne Russell, in Journal of a Trapper, observes: “Near where we encamped were several hot springs which boil perpetually.”

John Keeble