Hydrothermal /(?)/

Hy·dro·ther·mal

Hydrothermal

a.
  1. Of or pertaining to hot water; -- used esp. with reference to the action of heated waters in dissolving, redepositing, and otherwise producing mineral changes within the crust of the globe.
  2. of, pertaining to, or using the hot waters or steam found at special locations within the earth's crust; as, hydrothermal power generation.