soft coal . (a) A syn. of bituminous coal. Cf: hard coal. (b) Outside the U.S., the term is sometimes used for brown coal and/or lignite, or for any coal with a calorific value of 23.86 MJ/kg (10,260 BTU/lb) or less on a moist, mineral-matter-free basis.
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.
welded dike . A secundine dike whose boundaries have become obscured by continued mineral growth of the granitic country rock into the intrusion.
base-height ratio . The ratio between the air base and the flight height of a stereoscopic pair of aerial photographs.
centrum [paleont] (cen'-trum). (a) A differentiated central part of a sponge spicule. (b) The substance of a stem plate (columnal or cirral) of a crinoid, including luminal flanges. (c) The cylindrical part of a vertebra that chondrifies or ossifies around the notochord. Pl: centra.
vitroclastic (vit-ro-clas'-tic). Pertaining to a pyroclastic rock structure characterized by fragmented bits of glass; also, said of a rock having such a structure.
neft-gil (neft'-gil). A mixture of paraffins and a resin found in the Caspian area on Cheleken Island; it is related to pietricikite. Syn: neftdegil.
trough [sed struc] . The part of a ripple with an elevation of less than half its total height (Blatt et al., 1980).
ice lens [permafrost] . A discontinuous layer of ground ice tapering at the periphery; ice lenses in soil commonly occur parallel to each other in repeated layers.
flowage (flow'-age). (a) An act of flowing or flooding, such as the overflowing of a stream onto adjacent land; the state of being flooded. (b) A body of water resulting from flowage; the floodwater of a stream. The term is used locally in Wisconsin for the backwater of an artificial lake. (c) The area affected by a previous flooding.
pyroxene syenite . In Tobi's classification of the charnockite series (1971, p.202), a quartz-poor member having more microperthite than plagioclase; a mangerite-syenite.
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