Heat exchanger A device or engineered system that is used to transfer thermal energy in soil, rock or produced fluid...

Heat Mining The process of extracting geothermal heat by the heating of initially cold water that flows through...

Helium Isotopes Helium gas is a trace constituent of groundwater and thermal fluids, and the ratio of 3He to 4He can...

Hot Dry Rock Hot crystalline rock with essentially no porosity and lacking producible hot water. Geothermal production...

Hydraulic Fracture A rock-hosted tensile fracture that is created by injection of fluid under high pressure.

Hydraulic Gradient The slope on the water table which promotes horizontal fluid flow in permeable rock units.

Hydrothermal Eruption Rare explosive discharge of hot water and steam that is powerful enough to excavate a crater and...

Illite A potassium-bearing mica-like clay mineral that is a product of hydrothermal alteration. It commonly replaces...

INSAR Interferometric synthetic aperture radar is a technique that is deployed from aircraft or satellites in order to...

Interlayered Clay A mixture of different clays such as illite, chlorite, and montmorillonite that are structurally...

Lava Flow A product of an erupting volcanic cone or fissure made up of liquid molten rock that flows downhill and...

Liquid-Dominated Reservoir Typical of the large proportion of conventional geothermal resources in which wells are...