Other Energy and Geologic GLOSSARIES

aquifer
Layer of underground sand, gravel, or permeable rock in which water collects. Aquifers may lie close to the surface or at great depths. Aquifers can be hundreds of miles long and wide or narrow, shallow veins running through rock.

 

Anthracite
The highest rank of coal; used primarily for residential and commercial space heating. It is a hard, brittle, and black lustrous coal, often referred to as hard coal, containing a high percentage of fixed carbon and a low percentage of volatile matter.

bituminous coal
Middle rank coal (between subbituminous and anthracite) formed by additional pressure and heat on lignite. Usually has a high Btu value and may be referred to as "soft coal."

Btu (British thermal unit)  
The amount of heat needed to raise the temperature of 1 pound of water by 1 degree fahrenheit. The Btu is a convenient measure by which to compare the energy content of various fuels.

Cambrian
A period in the geologic time scale that spans from 570 to 505 million years ago.

carbon
A chemical element found in all living things.

carbon dioxide (CO2)
A colorless, odorless, incombustible gas formed during combustion in fossil-fuel electric generation plants.

cleat
The vertical cleavage of coal seams. The main set of joints along which coal breaks when mined.

coal
A readily combustible black or brownish-black rock whose composition, including inherent moisture, consists of more than 50 percent by weight and more than 70 percent by volume of carbonaceous material. It is formed from plant remains that have been compacted, hardened, chemically altered, and metamorphosed by heat and pressure over geologic time.

coke (coal)
A solid carbonaceous residue derived from low-ash, low-sulfur bituminous coal from which the volatile constituents are driven off by baking in an oven at temperatures as high as 2,000 degrees Fahrenheit so that the fixed carbon and residual ash are fused together. Coke is used as a fuel and as a reducing agent in smelting iron ore in a blast furnace. Coke from coal is grey, hard, and porous and has a heating value of 24.8 million Btu per short ton.

coke (petroleum)
A residue high in carbon content and low in hydrogen that is the final product of thermal decomposition in the condensation process in cracking. This product is reported as marketable coke or catalyst coke. The conversion is 5 barrels (of 42 U.S. gallons each) per short ton. Coke from petroleum has a heating value of 6.024 million Btu per barrel.

deposit
Mineral deposit or ore deposit is used to designate a natural occurrence of a useful mineral, or an ore, in sufficient extent and degree of concentration to invite exploitation.

drainage
The process of removing surplus ground or surface water either by artificial means or by gravity flow.

fossil
The remains of a plant or animal that lived long ago. Fossils are found in sedimentary rocks.

fossil fuel
A substance found in the layers of the Earth that can be burned and is formed by the remains of plants and animals that lived millions of years ago. Oil, natural gas, peat, and coal are fossil fuels.

geology
The scientific study of the origin, history, behavior, and structure of the Earth.

global warming
An increase in the average temperature of the Earth's surface, which occurs following an increase in greenhouse gases.

greenhouse effect
A complex natural process that takes place when gases in the Earth's atmosphere, including water vapor, allow heat energy from the Sun to pass through to the land and oceans. Heat energy radiating from the Earth's surface is absorbed by atmospheric gases, known as greenhouse gases, and is re-radiated back to Earth instead of escaping into space. This natural process may be affected by human activities, such as emitting large quantities of carbon dioxide into the atmosphere.

greenhouse gases
Gases that absorb heat re-radiated from the surface of the Earth. The greenhouse gases are carbon dioxide, chlorofluorocarbons (CFCs), methane, nitrous oxide, ozone, and water vapor.

kerosene
A light petroleum distillate that is used in space heaters, cook stoves, and water heaters and is suitable for use as a light source when burned in wick-fed lamps.

methane
A colorless, odorless gas composed of carbon and hydrogen. Methane occurs naturally in marshes, rice paddies, oil wells, and volcanoes. Methane is also formed in the digestive track of cattle and termites. Methane is a greenhouse gas in the atmosphere because it absorbs long-wavelength radiation from the Earth's surface.

mineral
A naturally occurring inorganic element or compound having an orderly internal structure and characteristic chemical composition.

recoverability
In reference to accessible coal resources, the condition of being physically, technologically, and economically minable. Recovery rates and recovery factors may be determined or estimated for coal resources without certain knowledge of their economic minability; therefore, the availability of recovery rates or factors does not predict recoverability.

Links to other glossaries:

Department of Energy Glossary
USGS Glossary
Geologic Glossary