Glaciology

2008/9 Schools Wikipedia Selection. Related subjects: Climate and the Weather

Lateral moraine on a glacier joining the Gorner Glacier, Zermatt, Switzerland. The moraine is the high bank of debris in the top left hand quarter of the picture. For more explanation, click on the picture.

Glaciology (from Middle French dialect (Franco-Provençal): glace, "ice"; or Latin: glacies, "frost, ice"; and Greek: λόγος, logos, "speech" lit. "to talk about ice") is the study of glaciers, or more generally ice and natural phenomena that involve ice.

Glaciology is an interdisciplinary earth science that integrates 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. The presence of ice on Mars and Europa brings in an extraterrestrial component to the field.

Overview

Areas of study within glaciology include glacial history and the reconstruction of past glaciation. A glaciologist is a person who studies glaciers. Glaciology is one of the key areas of polar research.

Types

There are two general categories of glaciation which glaciologists distinguish: alpine glaciation, accumulations or "rivers of ice" confined to valleys; and continental glaciation, unrestricted accumulations which once covered much of the northern continents.

• Alpine - ice flows down the valleys of mountainous areas and forms a tongue of ice moving towards the plains below. Alpine glaciers tend to make the topography more rugged, by adding and improving the scale of existing features such as large ravines called cirques and ridges where the rims of two cirques meet called arêtes.
• Continental - an ice sheet found today, only in high latitudes (Greenland/Antarctica), thousands of square kilometers wide and thousands of meters thick. These tend to smooth out the landscape.

Zones of glaciers

• Accumulation, where the formation of ice is faster than its removal.
• Wastage or Ablation, where the sum of melting and evaporation (sublimation) is greater than the amount of snow added each year.

Movement

Ablation 

wastage of the glacier through sublimation, ice melting and iceberg calving.

Arête 

an acute ridge of rock where two cirques abut.

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.

Cirque, corrie or cwm 

bowl shaped depression excavated by the source 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/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 in the bottom of a cirque when its 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.