The geothermal industry and the U.S. Geological Survey divide hydrothermal systems into two subclasses based on chemically determined maximum subsurface fluid temperatures: (1) high temperature fluids, which are generally defined as those fluids above 90 °C (~195 °F) and may be suitable for the generation of electricity, and (2) low and moderate temperature fluids, which are those that have likely maximum subsurface fluid temperatures below 90 °C (~195 °F). Moderate and low-temperature fluids may be suitable for direct use, such as industrial drying, aquaculture, and space heating. It is worth noting that not all high temperature systems relate to volcanoes. For example, there is no volcanic activity around the Dixie Valley hydrothermal power plant in Nevada (McKenna and Blackwell, 2004; Kennedy and van Soest, 2006).