There is huge heat energy in the center of the earth. When rainwater seeps into the ground or groundwater flows through the high-temperature and high-pressure areas at different depths inside the earth, the water will be heated into hot water or steam by the hot rock and released outward through the thick stratum. The energy generated by this "earth heat flow" is called geothermal energy. If the conditions for development and utilization are met, it will become a geothermal resource with development significance.
Geothermal resources can be divided into high temperature, medium temperature and low temperature according to temperature. Geothermal with temperature greater than 150 ℃ exists in the form of steam, which is called high-temperature geothermal; Geothermal at 90 ℃ ~ 150 ℃ exists in the form of a mixture of water and steam, which is called medium temperature geothermal; Geothermal below 90 ℃ exists in the form of water, which is called low-temperature geothermal.
In the Yarlung Zangbo River Valley in Tibet, magmatic activity is very frequent. There are many cracks underground. Water and steam with high temperature reach the surface through the cracks and release a lot of geothermal energy. Therefore, this place has become the most abundant place of geothermal resources in China.