Of, or relating to hot water. / (geology) Of or relating to emanations of hot water that are rich in minerals, or to the rocks formed from them.

(geology) the presence of hydrothermal activity / The commercial usage of hydrothermal streams

By hydrothermal means

Alternative form of hydrothermal

a hot spring, on the floor of the ocean, mostly along the central axes of the mid-ocean ridges, where heated fluids emerge from fissures in the Earth's crust.

plural of hydrothermal vent