Beta (β) decay. Nuclear decay in which a β particle (an electron ejected from a radioactive nucleus) is emitted or in which orbital electron capture occurs.

Breccia. A coarse-grained clastic rock, composed of angular broken rock fragments held together by a mineral cement or in a fine-grained matrix; it differs from conglomerate in that the fragments have sharp edges and unworn corners.

Calcrete. A term for a pedogenic calcareous soil, for example, limestone consisting of surficial sand and gravel cemented into a hard mass by calcium carbonate precipitated from solution and redeposited through the agency of infiltrating waters.

Caldera. A large, basin-shaped volcanic depression, more or less circular or cirquelike in form, formed by collapse during an eruption.

Carbonate. Sediments or rocks formed by the biotic or abiotic precipitation from aqueous solution of carbonates of calcium, magnesium, or iron, for example, limestone and dolomite. Aqueous carbonate species include CO2, H2CO3, and the HCO3 and CO32– ions.

Cataclasite. A fine-grained, cohesive rock with angular fragments that have been produced by the crushing and fracturing of preexisting rocks as a result of mechanical forces in the crust, normally lacking a penetrative foliation or microfabric.

Cohort. A group of individuals having a statistical factor (such as age or risk) in common.

Compaction. Any process, such as burial or desiccation, by which a soil mass loses pore space and becomes denser; or the densification of a soil by mechanical means, accomplished by rolling, tamping, or vibrating, usually at controlled water content.

Conglomerate. A coarse-grained clastic sedimentary rock, composed of rounded to subangular fragments larger than 2 mm in diameter (granules, pebbles, cobbles, boulders) typically containing fine-grained particles (sand, silt, clay) in the interstices, and commonly cemented by calcium carbonate, iron oxide, silica, or hardened clay.

Dewatering. The removal of water from a drowned shaft or waterlogged workings by pumping or drainage as a safety measure or as a preliminary step to resumption of development in the area.

Diagenesis. The sum of all chemical and physical changes in minerals during and after their initial accumulation, a process limited on the high-temperature, high-pressure side by the lowest grade of metamorphism.

Dike. A tabular igneous intrusion that cuts across the bedding or foliation of the country rock.

Dissolved load. The part of the total stream load that is carried in solution, such as chemical ions yielded by erosion of the landmass during the return of rainwater to the ocean.



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