Difference between revisions of "Glaciology" - New World Encyclopedia

From New World Encyclopedia
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; [[Ablation]] : In glaciology, ablation means wastage (depletion) of a glacier (or ice or iceberg) through such processes as sublimation, melting, and iceberg calving.
 
; [[Ablation]] : In glaciology, ablation means wastage (depletion) of a glacier (or ice or iceberg) through such processes as sublimation, melting, and iceberg calving.
 
; [[Arête]] : An arête is a thin, almost knife-like, ridge of [[Rock (geology)|rock]] that is typically formed when two [[glacier]]s erode adjacent, [[U-shaped valley]]s. It may also be formed when two glacial cirques erode headwards toward each other.
 
; [[Arête]] : An arête is a thin, almost knife-like, ridge of [[Rock (geology)|rock]] that is typically formed when two [[glacier]]s erode adjacent, [[U-shaped valley]]s. It may also be formed when two glacial cirques erode headwards toward each other.
; [[Bergshrund]] : crevasse formed near the head of a glacier, where the mass of ice has rotated, sheared and torn itself apart in the manner of a geological fault.
+
; [[Bergshrund]] : A crevasse formed near the head of a glacier, where the moving ice has torn itself apart from stationary ice, in the manner of a geological fault.
 
; [[Cirque (landform)|Cirque]] (coombe, combe, or corrie) : A bowl-shaped depression excavated by the head of a glacier.
 
; [[Cirque (landform)|Cirque]] (coombe, combe, or corrie) : A bowl-shaped depression excavated by the head of a glacier.
 
; [[Creep (deformation)|Creep]] : adjustment to [[Stress (physics)|stress]] at a [[Molecule|molecular]] level.
 
; [[Creep (deformation)|Creep]] : adjustment to [[Stress (physics)|stress]] at a [[Molecule|molecular]] level.
Line 32: Line 32:
 
; [[Fracture]] : brittle failure (breaking of ice) under the stress raised when movement is too rapid to be accommodated by creep. It happens for example, as the central part of a glacier movinges faster than the edges.
 
; [[Fracture]] : brittle failure (breaking of ice) under the stress raised when movement is too rapid to be accommodated by creep. It happens for example, as the central part of a glacier movinges faster than the edges.
 
; [[Pyramidal peak|Horn]] : spire of rock formed by the [[headward erosion]] of a ring of cirques around a single mountain. It is an extreme case of an arête.
 
; [[Pyramidal peak|Horn]] : spire of rock formed by the [[headward erosion]] of a ring of cirques around a single mountain. It is an extreme case of an arête.
; [[Plucking (glaciation)|Plucking]]/Quarrying : where the [[adhesion]] of the ice to the rock is stronger than the [[cohesion]] of the rock, part of the rock leaves with the flowing ice.
+
; [[Plucking (glaciation)|Plucking]] (or quarrying) : where the [[adhesion]] of the ice to the rock is stronger than the [[cohesion]] of the rock, part of the rock leaves with the flowing ice.
 
; [[Tarn (lake)|Tarn]] : a lake formed at the bottom of a cirque when the glacier has melted.
 
; [[Tarn (lake)|Tarn]] : a lake formed at the bottom of a cirque when the glacier has melted.
 
; [[Tunnel valley]] : The tunnel is that formed by hydraulic erosion of ice and rock below an ice sheet margin. The tunnel valley is what remains of it in the underlying rock when the ice sheet has melted.
 
; [[Tunnel valley]] : The tunnel is that formed by hydraulic erosion of ice and rock below an ice sheet margin. The tunnel valley is what remains of it in the underlying rock when the ice sheet has melted.

Revision as of 20:26, 7 August 2008

Lateral moraine on a glacier joining the Gorner Glacier in Zermatt, Switzerland. The moraine is the high bank of debris on the left side of the image.

Glaciology is the study of natural forms of ice, particularly glaciers, and phenomena related to ice. It includes the study of how glaciers are formed and depleted, how they move, and how they affect the physical landscape, the climate, and living organisms. It is one of the key areas of polar research. It also involves research into glacial history and the reconstruction of past glaciation, thus providing insights into the ice ages. The apparent presence of ice on Mars and Jupiter's moon Europa brings in an extraterrestrial component to the field.

Thus, glaciology is an interdisciplinary earth science, integrating geophysics, geology, physical geography, geomorphology, climatology, meteorology, hydrology, biology, and ecology. The impact of glaciers on humans adds the fields of human geography and anthropology. A person who studies glaciers is called a glaciologist.

Etymology

The word glacier can be traced to the Middle French dialect (Franco-Provençal) term glace, meaning "ice," derived from the Latin term glacies, meaning "frost" or "ice." The word "glaciology" is formed by combining this root with the Greek word λόγος (logos), meaning "speech" or "word."

Types

The process of glaciation is placed in two general categories, described below.

  • Alpine glaciation: It corresponds to accumulations or "rivers of ice" confined to valleys. As ice flows down the slopes of mountainous areas, it forms a "tongue" moving toward the plains below. Alpine glaciers tend to make the topography more rugged.
  • Continental glaciation: It corresponds to unrestricted ice sheets that once covered much of the northern continents but are now found only at high latitudes, such as in Greenland and Antarctica. The sheets are thousands of square kilometers wide and thousands of meters thick. They tend to smooth out the landscape.

Zones of glaciers

  • Accumulation zone: A zone where ice is formed faster than it is removed or lost.
  • Wastage or Ablation zone: A zone where the sum of melting and evaporation (sublimation) of ice is greater than the amount of snow added each year.

Terminology related to glacial movements and their effects

Striding Edge, an arête viewed from Helvellyn with the corrie Red Tarn to the left and Nethermost Cove to the right.
Ablation
In glaciology, ablation means wastage (depletion) of a glacier (or ice or iceberg) through such processes as sublimation, melting, and iceberg calving.
Arête
An arête is a thin, almost knife-like, ridge of rock that is typically formed when two glaciers erode adjacent, U-shaped valleys. It may also be formed when two glacial cirques erode headwards toward each other.
Bergshrund
A crevasse formed near the head of a glacier, where the moving ice has torn itself apart from stationary ice, in the manner of a geological fault.
Cirque (coombe, combe, or corrie)
A bowl-shaped depression excavated by the head of a glacier.
Creep
adjustment to stress at a molecular level.
Flow
movement (of ice) in a constant direction.
Fracture
brittle failure (breaking of ice) under the stress raised when movement is too rapid to be accommodated by creep. It happens for example, as the central part of a glacier movinges faster than the edges.
Horn
spire of rock formed by the headward erosion of a ring of cirques around a single mountain. It is an extreme case of an arête.
Plucking (or quarrying)
where the adhesion of the ice to the rock is stronger than the cohesion of the rock, part of the rock leaves with the flowing ice.
Tarn
a lake formed at the bottom of a cirque when the glacier has melted.
Tunnel valley
The tunnel is that formed by hydraulic erosion of ice and rock below an ice sheet margin. The tunnel valley is what remains of it in the underlying rock when the ice sheet has melted.

Glacial deposits

Stratified

Outwash sand/gravel
from front of glaciers, found on a plain
Kettles
block of stagnant ice leaves a depression or pit
Eskers
steep sided ridges of gravel/sand, possibly caused by streams running under stagnant ice
Kames
stratified drift builds up low steep hills
Varves
alternating thin sedimentary beds (coarse and fine) of a proglacial lake. Summer conditions deposit more and coarser material and those of the winter, less and finer.

Unstratified

Till-unsorted
(glacial flour to boulders) deposited by receding/advancing glaciers, forming moraines, and drumlins
Moraines
(Terminal) material deposited at the end; (Ground) material deposited as glacier melts; (lateral) material deposited along the sides.
Drumlins
smooth, elongated hills composed of till.
Ribbed moraines
large subglacial elongated hills, transverse to former ice flow.

See also

References
ISBN links support NWE through referral fees

  • Benn, Douglas I., and David J. A. Evans. 1998. Glaciers & Glaciation. London: Arnold. ISBN 0340584319.
  • Bennett, Matthew, and Neil F. Glasser. 1996. Glacial Geology: Ice Sheets and Landforms. Chichester: Wiley. ISBN 0471963453.
  • Hambrey, M. J., and Jürg Alean. 2004. Glaciers. 2nd ed. Cambridge, UK: Cambridge University Press. ISBN 978-0521828086.
  • Hooke, Roger LeB. 2005. Principles of Glacier Mechanics. 2nd ed. Cambridge, UK: Cambridge University Press. ISBN 978-0521836098.
  • Knight, Peter. 1999. Glaciers. Cheltenham: Stanley Thornes. ISBN 0748740007.

External links

General subfields within the earth sciences
Atmospheric sciences | Geodesy | Geology | Geophysics | Glaciology
Hydrology | Oceanography | Soil science


 Physical geography
Land ocean ice cloud 1024.jpg Biogeography · Climatology & paleoclimatology · Coastal/Marine studies · Geodesy · Geomorphology · Glaciology · Hydrology & Hydrography · Landscape ecology · Limnology · Oceanography · Palaeogeography · Pedology · Quaternary Studies

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