Glaciology
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Glaciology is the study of glaciers, or more generally the study of ice and natural phenomena that involve ice.
It is an interdisciplinary earth science that integrates geology, climatology, meteorology, hydrology, biology, and ecology. The discipline also forms a part of physical geography. The presence of ice on Mars and Europa brings in an extraterrestrial component to the field.
The word glacier is derived from the Latin glacies, meaning ice or frost.
Overview
A glacier is an extended mass of ice formed from snow falling and accumulating over a long period of time; glaciers move very slowly, either descending from high mountains, as in valley glaciers, or moving outward from centers of accumulation, as in continental glaciers.
Areas of study within glaciology include glacial history and the reconstruction of past glaciation. A glaciologist is a person who studies glaciers. A glacial geologist studies glacial deposits and glacial erosive features on the landscape. Glaciology and glacial geology are key areas of polar research.
Types
Glaciers can be identified by their geometry and the relationship to the surrounding topography. 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 arętes.
- Continental – an ice sheet found today, only in high latitudes (Greenland/Antarctica), thousands of square kilometers in area and thousands of meters thick. These tend to smooth out the landscapes.
Glacial Terminology
- Ablation
- Wastage of the glacier through sublimation, ice melting and iceberg calving.
- Ablation zone
- Area of a glacier in which the annual loss of ice through ablation exceeds the annual gain from precipitation.
- Aręte
- an acute ridge of rock where two cirques meet.
- Bergschrund
- 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 moves faster than the edges.
- Horn
- Spire of rock, also known as a pyramidal peak, formed by the headward erosion of three or more cirques around a single mountain. It is an extreme case of an aręte.
- 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 post-glacial lake in a cirque.
- Tunnel valley
- The tunnel that is 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.