differential erosion . Erosion that occurs at irregular or varying rates, caused by the differences in the resistance and hardness of surface materials: softer and weaker rocks are rapidly worn away, whereas harder and more resistant rocks remain to form ridges, hills, or mountains. Syn: etching.
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.
corona [bot] (co-ro'-na). In charophyte algae, the outer layer of the nucule, formed by cells cut off from the sheath cells of the female sex organ.
grease ice . A soupy layer of new ice formed on a water surface (esp. in the sea) by the coagulation of frazil crystals; it reflects little light, giving the sea a matte, greasy appearance. Syn: ice slush.
neutral density . A value assiged to all parcels of water on the same neutral surface. It has units of density. It is a function of salinity, in-situ temperature, pressure, latitude and longitude.
tropical lake . (a) A lake in the tropics. (b) A lake whose surface temperature never falls below the temperature of maximum-density water, about 3.96°C. The appropriateness of this sense of the term has been questioned, since it has identified lakes in Switzerland and Scotland. Cf: polar lake.
model scale . The relationship existing between a distance measured in a model (such as in a stereoscopic image) and the corresponding distance on the Earth.
half-moon cut . A style of gem cutting that produces a stone in the shape of a half circle.
interplanetary dust particles . (a) Submillimeter particles in space. (b) Submillimeter interplanetary particles collected for scientific study (particularly in the stratosphere by impactors carried on aircraft). Abbrev: IDP.
air base . An imaginary line connecting the points in space at which successive photos in a flight strip were taken; specif., the length of such a line (ASP, 1975, p.2064). Cf: photobase.
glaciology (gla-ci-ol'-o-gy). (a) The study of all aspects of snow and ice; the science that treats quantitatively the whole range of processes associated with all forms of solid water. Syn: cryology. (b) The study of existing glaciers and ice sheets, and of their physical properties. This definition is not internationally accepted.
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