GeoWord of the Day

The GeoWord of the Day is a free service of the American Geosciences Institute. All of the terms and definitions are from the Glossary of Geology, 5th Edition Revised.

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submarine volcano . A volcano on the ocean floor, commonly of basalt. See also: volcanic island.

hyaline element . A conodont element that lacks white matter except, perhaps, along thin growth axes in cusp or denticles; contrasts with albid element; typical fibrous elements are also hyaline, but it is not clear that all hyaline elements are fibrous in structure (TIP, 1981, pt. W, supp.2).

silhydrite (sil-hy'-drite). A white orthorhombic mineral: 3SiO2•H2O .

subsystem [chem] (sub-sys'-tem). Any part of a system that may be treated as an independent system.

trail of a fault . Crushed material along the fault surface that is used, often erroneously, as an indication of the direction of displacement. Such material can be a source of mineral deposits ( drag ore ). Little used.

longitudinal ridge . One of many closely spaced continuous ridges elongated parallel to the current and developed rhythmically on all or part of a stream bed. Ridges are separated by regularly spaced longitudinal furrows, the separation ranging from 3 mm to as much as 5 cm (Dzulynski and Walton, 1965, p.61). Cf: rib and furrow.

sechron (se'-chron). The maximum interval of geologic time occupied by a given depositional sequence, defined at the points where the boundaries of the sequence change laterally from unconformities to conformities along which there is no significant hiatus (Mitchum, 1977, p.210).

Pierson-Moskowitz wave spectrum . An idealized form of the wave spectrum, which represents the ocean waves generated by a constant, homogeneous wind blowing for many days over the ocean.

gastrovascular cavity (gas'-tro-vas'-cu-lar). The interior space ( coelenteron ) of a coral polyp, radially partitioned by septa, and functioning in both digestion and circulation.

intercision (in-ter-ci'-sion). (a) A type of capture characterized by sidewise swinging of mature streams (Lobeck, 1939, p.201). (b) A type of diversion accomplished by the cutting back of bluffs along a lake shore such that the lake advances inland and cuts into a bend of a river valley some distance above its mouth (Goldthwait, 1908).


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