How hot are geysers?
A geyser eruption starts as the cooler water at the surface reaches the boiling point. The boiling point of a liquid is dependent upon the pressure. The boiling point of pure water 212 degrees Fahrenheit (100 degrees Celsius) at sea level. In Yellowstone the elevation is about 7,500 feet, the pressure is lower, and the boiling point of water is only about 199 degrees Fahrenheit (93 degrees Celsius). The rising water coming from the volcanic source at depth is superheated to temperatures well above 200 degrees. At the surface most geysers are 199 to 215 degrees Fahrenheit which is at or just above the boiling point just before and during an eruption. For geysers to erupt the water must be at or above the boiling point.
