Includes temperature differences related to the Earth's internal heat, commonly observed as springs or vents discharging hot water or steam, or through geothermal wells positioned to extract heat. Distributions are direct observations of the temperature and flow volume of springs, vents, or deep-lying heat sources, as well as geologic and hydraulic models that estimate the location, temperature, and flow rate of hot water. Assessments evaluate geothermal energy potential, risks, and effects on other resources and uses. Predictions are the results of models or projections of future energy potential, risks, and effects; these data include predicted changes due to economic, regulatory, technological, and environmental changes.