The formation of hot springs can generally be divided into two types:
One is formed by magmatism in the crust, or accompanied by volcanic eruptions. The extinct volcanic terrain area that has undergone volcanic activity, the surface uplifted by the movement of the crustal plates, and the uncooled magma beneath it will continue to Release a large amount of heat energy. Because of the concentration of heat from such heat sources, as long as there are pores nearby, the water-bearing rock formation will not only be heated into high-temperature hot water, but most of it will boil into steam, mostly sulfate springs.
The second is formed by the circulation of surface water. That is to say, when rainwater drops to the surface and penetrates downwards, the aquifers deep in the crust form groundwater (sandstone, conglomerate, volcanic rock, these good aquifers). Groundwater is heated by the geothermal below to become hot water. Most of the deep hot water contains gas, which is mainly carbon dioxide. When the temperature of the hot water rises, if there is a dense, impermeable rock layer above it, the pressure will become higher and higher. , So that the hot water and steam are in a high-pressure state, and cracks will rush up. As the hot water rises, the pressure gradually decreases as it approaches the surface. As the pressure gradually decreases, the contained gas gradually expands, reducing the density of the hot water. These expanded vapors are more conducive to the rise of the hot water. The rising hot water and the late sinking cold water produced by the pressure (hydrostatic pressure difference) repeatedly circulate to produce convection. When the resistance of the open fissure is small, the hot water will rise through the fissure and gush out of the ground. That is, it will rise continuously and eventually flow out of the ground to form a hot spring. With the combination of high mountain and deep valley topography, the surface water at the bottom of the valley may be higher than the mountain, and the water level in the middle and ground is low. Therefore, the bottom of the deep valley may be the place where the hydrostatic pressure difference is the largest. The hot water upwelling should also be the most likely to gush from the valley bottom. Occurs on the riverbed in the valley.