hot spring, natural discharge of groundwater having an elevated temperature. Most hot springs result from the emergence of groundwater that has passed through or near recently formed, hot, igneous rocks. Iceland, Yellowstone Park in the United States, and North Island of New Zealand are noted for their hot springs. In recent years the depletion of fossil fuels has resulted in a renewed interest in utilizing the energy contained in hot springs. This type of geothermal energy is already being utilized in California, Italy, and Iceland. See energy, sources of.

or thermal spring

Spring that issues water at temperatures substantially higher than the air temperature of the surrounding region. Most hot springs result from the interaction of groundwater with magma or with solid but still-hot igneous rocks. Some, however, are not related to volcanic activity. In such cases, deep circulation of water is thought to carry the water to the lower parts of the Earth's crust, where the temperature of the rocks is high.

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