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Dynamic Planet
Glaciers
| Question | Answer |
|---|---|
| Cirque glaciers | Named for the bowl-like hollows they occupy. Typically, they are found high on mountainsides and tend to be wide rather than long. |
| Piedmont glaciers | Steep valley glaciers spill into relatively flat plains, where they spread out into bulb-like lobes. The Malaspina Glacier in Alaska, covering over 5,000 square kilometers is one of the most famous examples of this type of glacier. |
| Ice field | Similar to ice caps, except that their flow is influenced by the underlying topography, and they are typically smaller than ice caps. |
| Ice sheets | Found only in Antarctica and Greenland, they are enormous masses of glacial ice and snow that cover over 50,000 square kilometers. |
| Head | Top of glacier. |
| Terminus | End or snout of a glacier. |
| Snow line | The minimum elevation of snow lying on the ground or glacier surface. At the end of an ablation season, this marks a glacier’s current equilibrium line. |
| Equilibrium line altitude | The altitude on a glacier where the annual addition (accumulation) of mass is exactly compensated by the annual disappearance (ablation) of mass, induces an immediate step change in specific mass balance (b = total mass change divided by glacier area). |
| Ablation zone | Area or zone of a glacier where snow and ice ablation exceeds accumulation. It generally occurs at lower (warmer) elevations. |
| Lateral moraine | A ridge-shaped moraine deposited at the side of a glacier and composed of material eroded from the valley walls by the moving glacier. |
| Medial moraine | A ridge-shaped moraine in the middle of a glacier originating from a rock outcrop, nunatak, or the converging lateral moraines of two or more ice streams. |
| Moraine | A mound, ridge, or other distinct accumulation of glacial till. |
| Sun cups | Ablation hollows that develop during intense sunshine. |
| Albedo | The fraction of light that is reflected by a body or surface. |
| Erosion | The act or operation of eroding, or eating away. |
| Deposition | The natural process of laying down a deposit of something. |
| Crevasse | An open fissure in the glacier surface |
| Extensional flow | When glacier motion is accelerating down-slope |
| Insolation | The part of the sun's radiation that is transmitted to the surface to the glacier directly; re-emission is the portion of the sun's radiation that is absorbed by particles in the atmosphere and then projected to the earth's surface. |
| Solar variability | Changes in amount of radiation emitted by the sun. |
| Obliquity | Change in angle of earth's axis to plane of earth's orbit; 41,000 year cycle |
| Precession | Cycle of wobble in earth's axis = 23,000 years |
| Epoch | A particular period of history, especially one considered remarkable or noteworthy. |
| Interglacial periods | Times without large ice-sheets |
| Ogives | Alternate bands of light and dark ice seen on a glacier surface |
| Glacial erratic | A large boulder that has been carried to its resting place by glacial ice |
| Glacial striations | Glacial abrasions sometimes are evident in the long scratches and grooves in the bedrock |
| Chatter marks | Marks on a glaciated rock caused by the movement of a glacier |
| Arêtes | Forms when two glaciers work on opposite sides of the same wall, leaving a long narrow ridge |
| Horns | Result when glaciers carve three or more sides of a mountain, often honing it to a pyramid-shaped peak |
| Drumlin | A hilly remnant from the ice ages |
| Calving | Process by which ice breaks off a glacier's terminus |
| Compressing flow | Flow that occurs when glacier motion is decelerating down-slope |
| Creep | A way that snow or ice can move by deforming its internal structure |
| Drift glacier | A glacier that receives nourishment from wind-blown snow |
| Esker | A sinuous ridge of sedimentary material (typically gravel or sand) deposited by streams that cut channels under or through the glacier ice |
| Foliation | Layering in glacier ice that has distinctive crystal sizes and/or number of bubbles |
| Glacial till | Accumulations of unsorted, unstratified mixtures of clay, silt, sand, gravel, and boulders; the usual composition of a moraine |
| Hanging glacier | A glacier that terminates at or near the top of a cliff |
| Headwall | A steep cliff, usually the uppermost part of a cirque |
| Ice quake | A shaking of ice caused by crevasse formation or jerky motion |
| Ice stream | A current of ice in an ice sheet or ice cap that flows faster than the surrounding ice. 2. Sometimes referring to the confluent sections of a branched-valley glacier. 3. Obsolete synonym of valley glaciers. |
| Ice worm | An oligochaete worm that lives on temperate glaciers or perennial snow. There are several species that range in color from yellowish brown to reddish brown or black. They are usually less than 1 millimeter (.04 in) in diameter and average about 3 millimet |
| Iceberg | A piece of ice that has broken off from the end of a glacier that terminates in water |
| Penitents | The extreme relief of ablation hollows found most often at high altitudes in the tropics. The resulting spikes of snow resemble repentant souls. |
| Polar glacier | A glacier whose temperatures are below freezing throughout, except possibly for a thin layer of melt near the surface during summer or near the bed. They are found only in Polar Regions of the globe or at high altitudes. |
| Pothole | A 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. Also called a glacier mill. |
| Pressure melting | Melting that occurs in ice at temperatures colder than normal melting temperature because of added pressure |
| Reconstituted glacier | A glacier that is reconstructed or reconstituted out of other glacier material; usually formed by sercas falling from a hanging glacier then re-adhering |
| Retreat | When the position of a mountain glacier's terminus is farther up-valley than before. Glacial retreat occurs when a glacier ablates more material at its terminus than it transports into that region. |
| Snow worm | An oligochaete worm that lives on temperate glaciers or perennial snow. There are several species that range in color from yellowish brown to reddish brown or black. They are usually less than 1 millimeter (.04 in) in diameter and average about 3 millimet |
| Tarn | A small mountain lake or pool |
| Sublimation | The change of state from ice to water vapor or water vapor to ice |
| Zone of equilibrium | Zone of a glacier in which the amount of precipitation that falls is equal to the amount that melts the following summer |
| Irradiation flux | When short wave radiation first strikes a surface other than the glacier on the ground and then is transmitted to the glacier surface. |
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tbjh
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