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Glossary
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a special form of solid clathrate compound in which crystal lattice cages or chambers, consisting of host molecules, enclose guest molecules.
gaugein meteorology, general term for any device that measures strength of wind, pressure, and other parameters; the most widespread gauges on meteorology are balance snow gauge, barometer gauge, density-of-snow gauge, dew gauge, distance gauge, rain-and snow gauge, rain-intensity gauge, standard gauge, wind gauge, etc..
gelifluctionthe slow downslope flow of unfrozen earth materials on a frozen substrate.
general circulationof the atmosphere; complete statistical description of atmospheric motions over the earth.
general circulation modelnumerical representation of the atmosphere and its phenomena over the entire earth, using the equations of motion and including radiation, photochemistry, and the transfer of heat, water vapor, and momentum.
geocryologythe study of earth materials having a temperature below 0 degrees Celsius.
geomagnetic polethe point of intersection of the Earth's surface with the axis of a simple magnetic dipole that best approximates the Earth's actual, more complex magnetic field; if the Earth's magnetic field were a perfect dipole then the field lines would be vertical at the geomagnetic poles, and they would therefore coincide with the magnetic poles: however, the dipole approximation is in fact far from perfect, so in reality the magnetic and geomagnetic poles lie some distance apart.
geostrophic windtheoretical wind which results from the equilibrium between horizontal components of the pressure gradient force and the coriolis force (deviating force) above the friction layer; only these two forces (no frictional force) are supposed to act on the moving air; it blows parallel to straight isobars or contours.
geothermal gradientthe rate of temperature increase with depth in the subsurface.
geothermal heat fluxthe amount of heat moving steadily outward from the interior of the earth through a unit area in unit time.
geyserfountain that develops when water from a conduit is forced up to the surface of a glacier; also called a negative mill.
glacial advancewhen a mountain glacier's terminus extends farther downvalley than before; occurs when a glacier flows downvalley faster than the rate of ablation at its terminus.
glacial erratica boulder swept from its place of origin by glacier advance or retreat and deposited elsewhere as the glacier melted; after glacial melt, the boulder might be stranded in a field or forest where no other rocks of its type or size exist.
grooves or gouges cut into the bedrock by gravel and rocks carried by glacial ice and meltwater; also called glacial striations.
when the position of a mountain glacier's terminus is farther upvalley than before; occurs when a glacier ablates more material at its terminus than it transports into that region.
grooves or gouges cut into the bedrock by gravel and rocks carried by glacial ice and meltwater; also called glacial grooves.
accumulations of unsorted, unstratified mixtures of clay, silt, sand, gravel, and boulders; the usual composition of a moraine.
glacial trougha large u-shaped valley formed from a v-shaped valley by glacial erosion.
land covered in the past by any form of glacier is said to be glaciated.
glaciera mass of ice that originates on land, usually having an area larger than one tenth of a square kilometer; many believe that a glacier must show some type of movement; others believe that a glacier can show evidence of past or present movement.
a cave of ice, usually underneath a glacier and formed by meltwater; cave entrances are often enlarged near a glacier terminus by warm winds; most common on stagnant portions of glaciers.
a phenomenon in which strong reflection of the sun on an icy surface causes a glacier to look like it is on fire.
glacier flooda sudden outburst of water released by a glacier.
glacier floura fine powder of silt- and clay-sized particles that a glacier creates as its rock-laden ice scrapes over bedrock; usually flushed out in meltwater streams and causes water to look powdery gray; lakes and oceans that fill with glacier flour may develop a banded appearance; also called rock flour.
glacier icewell-bonded ice crystals compacted from snow with a bulk density greater than 860 kilograms per cubic-meter (55 pounds per cubic-foot).
glacier milla nearly vertical channel in ice that is formed by flowing water; usually found after a relatively flat section of glacier in a region of transverse crevasses.
glacier potholepotholes formed at the bottom of glaciers through erosion caused by sand and gravel in melt-water; melt-water seeps through crevasses in the glaciers, sometimes forming whirpools; at the bottom of the glacier, the water is under very high pressure, leading to erosion of underlying rocks.
glacier remainiea glacier that is reconstructed or reconstituted out of other glacier material; usually formed by seracs falling from a hanging glacier, then re-adhering; also called reconstituted, reconstructed or regenerated glacier.
glacier snoutthe lowest end of a glacier; also called glacier terminus or toe.
the bottom of the ice of a glacier.
glacier tablea rock that resides on a pedestal of ice; formed by differential ablation between the rock-covered ice and surrounding bare ice.
the lowest end of a glacier; also called glacier snout or toe.
the lowest end of a glacier; also called glacier snout or terminus.
an extension of a glacier or ice stream projecting seaward, usually afloat.
glacier troughu-shaped valleys transformed from v-shaped stream valleys due to erosion caused by passing glaciers.
glacier winda localized current of air occuring as a result of a glacier's melting processes; when the surface of glacial ice melts, the air above the glacier cools and becomes heavier than the surrounding air and flows down the glacial valley; glacier wind can also be wind that flows out of ice caves; a kind of katabatic wind.
glaciereta very small glacier.
land overlaid at present by a glacier is said to be covered; the alternative term glacierized has not found general favour.
glazea coating of ice, generally clear and smooth but usually containing some air pockets, formed on exposed objects by freezing of a film of super-cooled water deposited by rain, drizzle, fog, or possibly condensed from super-cooled water vapor; glaze is denser, harder and more transparent, than either rime or hoarfrost.
global observing systemglobal network of observational stations which is the coordinated system of methods, techniques and facilities for making observations on a world-wide scale in the framework of the World Weather Watch, a World Meteorological Organization program.
the coordinated global system of telecommunication facilities and arrangements for the rapid collection, exchange and distribution of observational data in the framework of the World Weather Watch, a World Meteorological Organization program.
the same as geostrophic wind, but blowing parallel to curved isobars or contours; the curved airflow pattern around a pressure center results from a balance among pressure-gradient force, coriolis force, and centrifugal force.
a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form discrete loosely packed units.
granoidic cryogenic fabrica distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form more or less discrete loosely packed units.
graupelsnowflakes that become rounded pellets due to riming; typical sizes are 2 to 5 millimeters in diameter (0.1 to 0.2 inch); graupel is sometimes mistaken for hail.
gravimetric (total) water contentthe ratio of the mass of the water and ice in a sample to the dry mass of the sample, commonly expressed as a percentage.
gravity wavea wave disturbance in which buoyancy (or reduced gravity) acts as a restoring force on parcels displaced from hydrostatic equilibrium; there is a direct oscillatory conversion between potential and kinetic energy in the wave motion.
a cold wind blowing down an incline; a kind of katabatic wind.
grease icea very thin, soupy layer of frazil crystals clumped together, which makes the ocean surface resemble an oil slick.
the anticyclone that appears to overlie Greenland; analogous to the antarctic anticyclone.
a category of young ice 15 to 30 centimeters (6 to 12 inches) thick, named for its color.
a finite collection of points to which the meteorological variables used in a numerical model, or interpolated from observations, apply; a field of such regular values (points) is termed gridded field.
a general term referring to all types of ice contained in freezing and frozen ground.
ground morainecontinuous layer of till near the edge or underneath a steadily retreating glacier.
growleran iceberg less than 2 meters (6.6 feet) across that floats with less than 1 meter (3.3 feet) showing above water; smaller than a bergy bit.
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