A large, bowl-shaped crater associated with a volcanic vent. A caldera can form from a volcanic blast or the collapse of a volcanic cone into an emptied magma chamber.
A rock made up primarily of carbonate minerals (minerals containing the CO
3 anionic structure). Limestone (made up primarily of calicite - CaCO
3) and dolostone (made up primarily of dolomite - CaMg (CO
3)
2 are the most common examples.
A weak acid (H
2CO
3) that forms from the reaction of water and carbon dioxide. Most rain water is a very weak carbonic acid solution formed by the reaction of rain with small amounts of carbon dioxide in the atmosphere.
The costs incurred by a lessee to retain exploration and property rights after acquisition but before production begins. Carrying costs can include: ad valorem taxes on non-producing mineral properties, shut-in royalties, and delay rentals.
A breccia of powdered rock formed by crushing and shearing during tectonic movements.
A solid precipitate of calcium carbonate, silica, iron oxide, clay minerals or other materials that forms within the pore spaces of a sediment and binds it into a sedimentary rock.
The processes through which chemical precipitates form within the pore spaces of a sediment and help bind it into a sedimentary rock.
A rock that forms from the precipitation of mineral material from solution. Examples are chert and rock salt.
The breaking down of surface rock material by solution or chemical alteration. Common alteration processes are oxidation and hydrolysis.
A microcrystalline or cryptocrystalline sedimentary rock material composed of SiO
2. Occurs as nodules and concretionary masses and less frequently as a layered deposit. Picture of Chert.
The valves, pipes and fittings installed above ground surface at an oil or gas well site. These control and direct the flow of natural gas or oil produced from the well.
The lowest horizon of a soil profile. It is below the B-horizon and is made up of weathered bedrock.
A cone-shaped hill that consists of pyroclastic materials ejected from a volcanic vent.
A bowl-shaped depression with very steep sides that forms at the head of a mountain glacier. Forms from cold-climate weathering processes including frost wedging and plucking.
A sedimentary rock (such as shale, siltstone, sandstone or conglomerate) or sediment (such as mud, silt, sand, or pebbles). An accumulation of transported weathering debris.
A clastic mineral particle of any composition that has a grain size smaller than 1/256 mm. The term is also used in reference to a broad category of hydrous silicate minerals in which the silica tetrahedrons are arranged into sheets.
A brown or black sedimentary rock that forms from accumulated plant debris. A combustible rock that contains at least 50% (by weight) carbon compounds.
The process of converting solid coal into gas, usually by heating. The gas is then used as a fuel or processed into a chemical or liquid fuel.
The process of converting solid coal into a liquid fuel such as synthetic crude oil or methanol.
An area of low relief along a continental margin that is underlain by thick, gently dipping sediments.
A compression process that reorients and reshapes the grains of a sediment in response to the weight of overlying deposits.
A cone-shaped volcanic mountain composed of alternating layers of cinders and lava flows. Also known as a stratovolcano.
A cone-shaped lowering of the water table around a producing well.
A clastic sedimentary rock that contains large (greater then two millimeters in diameter) rounded particles. The space between the pebbles is generally filled with smaller particles and/or a chemical cement that binds the rock together. Picture of Conglomerate.
Alteration of a rock, mainly by heat, which occurs adjacent to a dike, sill, magma chamber or other magma body.
A line on a map that traces locations where the value of a variable is constant. For example, contour lines of elevation trace points of equal elevation across the map. All points on the "ten foot" contour line are ten feet above sea level.
A map that shows the change in value of a variable over a geographic area through the use of contour lines. For example, a contour map of elevation has lines that trace points of equal elevation across the map. See also: contour line and topographic map.
A liquid hydrocarbon produced from natural underground reservoirs. It might also include liquid hydrocarbons produced from tar sands, gilsonite, and oil shale. Crude oil can be refined into a number of petroleum products which include: heating oil, gasoline, diesel fuel, jet fuel, lubricants, asphalt, ethane, propane, butane, and many other products.
A unit of measure frequently used to quantify the rate of flow of a stream. It is equal to a volume of water one foot high and one foot wide moving a linear distance of one foot in one second.