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.


hyperconcentrated flow . A gravitationally driven, nonuniform mixture of debris and water, having water content larger than that of a debris flow but less than that of a muddy streamflow (Vallance, 2000).

dihexagonal prism . A crystal form of twelve faces parallel to the symmetry axis, in which any cross section perpendicular to the prism axis is dihexagonal. Its indices are { hk 0} with symmetry 6/ m 2/ m 2/ m .

örebroite (ö-re-bro'-ite). A dark brown trigonal mineral of the welinite group: Mn2+3(Sb5+,Fe3+)(SiO4)(O,OH)3 .

seam [ore dep] . A particular bed or vein in a series of beds; it is usually said of coal but may also pertain to metallic minerals.

mcauslanite (mc-aus'-lan-ite). A yellowish-white triclinic mineral: HFe2+3Al2(PO4)4F•18H2O .

choristopore (cho-ris'-to-pore). The most advanced position of reproductive organs in dasycladacean algae, in which cysts are in gametangia located in the second- or third-order branches (laterals). Cf: cladospore.

phenomenal gem (phe-nom'-e-nal). A gemstone exhibiting an optical phenomenon, such as asterism, chatoyancy, or play of color.

geotectonics (ge''-o-tec-ton'-ics). The term used for tectonics when the features being described are of regional scale or larger. Cf: megatectonics.

primary tectogenesis . Vertical uplift over a geotumor (Haarmann, 1930). Obsolete.

morro (mor'-ro). A term used in Latin America for an isolated hill or ridge, which may or may not be on a coastal plain near the present shoreline; esp. a headland or bluff. Etymol: Spanish and Portuguese.

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