volcanic rock

volcanic rock . (a) A generally finely crystalline or glassy igneous rock resulting from volcanic action at or near the Earth's surface, either ejected explosively or extruded as lava; e.g. basalt. The term includes near-surface intrusions that form a part of the volcanic structure. See also: volcanics. Cf: plutonic rock. (b) A general term proposed by Read (1944) to include the effusive rocks and associated high-level intrusive rocks; they are dominantly basic. Cf: neptunic rock; plutonic rock.


mesonorm (mes'-o-norm). Theoretical calculation of normative minerals in metamorphic rocks of the mesozone from chemical analyses (Barth, 1959). Cf: catanorm; epinorm. See also: Niggli molecular norm.

foot [geol]

foot [geol] . (a) The bottom of a slope, grade, or declivity. Cf: head [geomorph]. (b) That portion of the displaced material of a landslide that lies downslope from the toe of the surface of rupture (Varnes, 1978). (c) The lower bend of a fold or structural terrace. Syn: lower break.


hause . An English term for a pass, or a ridge connecting two higher elevations, or a narrow gorge (Whitney, 1888, p.137). Cf: hals. Syn: haws.


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