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Geological Terms Beginning With "H"



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Half-Life

Half-Life

The time required for one half of a radioactive substance to decay into its daughter material.

Halite

Halite

The mineral name for "rock salt". A chemical sedimentary rock that forms from the evaporation of ocean or saline lake waters. It is rarely found at Earth's surface, except in areas of very arid climate. It is often mined for use in the chemical industry or for use as a winter highway treatment. Some halite is processed for use as a seasoning for food.

hand lens

Hand Lens

A small magnifying glass of about 10x power that is used in the field, office and laboratory by geologists to examine rock, mineral, fossil and other specimens. It is usually a folding device with a metal cover that, when closed, protects the lens from scratches and impact. Also known as a "hand magnifier", "pocket magnifier" or a "pocket lens". See this item in the Geology.com Store.

Hanging Valley

Hanging Valley

A tributary to a U-shaped glacial valley which, instead of entering the valley at the same level as the main stream, enters at a higher elevation, frequently as a waterfall. These different stream levels are a result of the rapid downcutting of the glacier being much faster than the slower downcutting of the tributary stream.

Hard Water

Hard Water

Water that has a significant amount of dissolved calcium and magnesium ions. This water performs poorly with most soaps and detergents and leaves a scaly deposit in containers where it is heated or evaporates. It can frequently be improved through the use of home-based water treatment systems.

Hardness

Hardness

The resistance of a mineral to being scratched. Typically measured using the Mohs Hardness Scale.

head

Head

The upper part of a landslide's moving mass. It is located immediately below the scarp. Often when the scarp of a landslide becomes visible people will place soil on the head area to reestablish a smooth slope. This can be a mistake because it adds weight to the head and drives the slide.

Headwater(s)

Headwater(s)

The upper portions of a drainage basin where the tributaries of a stream first begin flow.

Heat Flow

Heat Flow

The movement of heat energy from the core of the Earth towards the surface.

Heliodor

Heliodor

Heliodor is the name given to yellow to yellow-green gems of the beryl mineral group. They can be attractive, durable, high-clarity stones with a relatively low price. Surprisingly, they are infrequently seen in jewelry.

Hematite

Hematite

An iron oxide mineral with a chemical composition of Fe2O3. It is the world's most important ore of iron. When crushed it forms a red powder that has been used as a pigment for thousands of years.

Hemimorphite

Hemimorphite

Hemimorphite is a zinc silicate mineral that occurs in white, blue and greenish blue colors. It is a minor ore of zinc. It is sometimes cut as a gemstone. These lack durability and are used as a collector's gem or in jewelry that will be subject to light wear.

hessonite garnet

Hessonite Garnet

Hessonite is a variety of grossular garnet that is rich in iron and manganese. It has an orange to red-orange to reddish brown color and is sometimes called "cinnamon stone." It is occasionally cut into faceted stones and used in jewelry.

Hogback

Hogback

A narrow ridge with steeply inclined sides of nearly equal slopes. Formed by differential erosion of steeply dipping rock units.

hoodoo

Hoodoo

An unusual pillar of rock that remains after the differental weathering or erosion of horizontal rock layers of varying physical properties. These structures can be caused by weathering along joints, less resistant rock units being selectively weathered, remnants from stream erosion and other processes. The name has an African origin where people imagined hoodoos being evil spirits or creatures in the form of stone.

Hornfels

Hornfels

A nonfoliated metamorphic rock that is typically formed by contact metamorphism around igneous intrusions.

hoodoo

Hornito

A small spatter cone that forms on the solidified surface of a lava flow where hot lava is still flowing below. An opening in the roof of the flow and pressure within can force a spattering of lava out of the opening. This lava can build up into a structure with a very unusual shape.

Horst

Horst

An elongated block of high topographic relief that is bounded on two sides by steep normal faults. Produced in an area of crustal extension.

host rock

Host Rock

The barren rock that surrounds a mineral deposit. It is a term that is more specific and less geographically extensive than "country rock". Shown in the photo is gold in a quartz vein (right side) enclosed in basalt (left side).

Hot Spot

Hot Spot

A volcanic center located within a lithospheric plate that is thought to be caused by a plume of hot mantle material rising from depth and located above a "hot spot" on the outer core.

Hot Spring

Hot Spring

A natural spring that delivers water to the surface that is of higher temperature than the human body.

Humus

Humus

The dark portion of a soil that consists of organic material that is well enough decayed that the original source material can not be identified.

Hydraulic Conductivity

Hydraulic Conductivity

The ability of a porous material to transmit a fluid. Permeability.

Hydrocarbon

Hydrocarbon

Any organic chemical compound (gaseous, liquid or solid) that is composed of carbon and hydrogen. The term is frequently used in reference to fossil fuels, specifically crude oil and natural gas.

Hydroelectric power

Hydroelectric power

The production of electrical energy through the use of flowing or falling water.

Hydrograph

Hydrograph

A graph that shows the change of a water-related variable over time. Example: A stream discharge hydrograph shows the change in discharge of a stream over time.

Hydrologic Cycle

Hydrologic Cycle

The natural cycling of Earth's water between the atmosphere, surface and subsurface through the processes of evaporation, transpiration, percolation, infiltration, runoff and precipitation.

Hydrology

Hydrology

The science of Earth's water, its movement, abundance, chemistry and distribution on, above and below Earth's surface.

Hydrolysis

Hydrolysis

A chemical reaction involving water that results in the breakdown of mineral material.

Hydrothermal

Hydrothermal

Pertaining to hot water, the actions of hot water or the products produced by the actions of hot water.

Hydrothermal Deposits

Hydrothermal Deposits

Mineral deposits that are formed by the actions of hot water or gases associated with a magmatic source.

Hydrothermal Metamorphism

Hydrothermal Metamorphism

Alteration of rock by hot waters or gases associated with a magmatic source.

Hydrothermal Vein

Hydrothermal Vein

A deposit of minerals precipitated in a fracture by the actions of hot water or gases associated with a magmatic source.

Hypocenter

Hypocenter

A point beneath earth's surface where the vibrations of an earthquake are thought to have originated. Also known as the focus.

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