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Atmosphere of Earth

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.

Bylot Island glacier, Sirmilik National ParkNunavut. This mountain glacier is one of many coming down from the interior ice cap on top of the Byam Martin Mountains.

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 arêtes.
  • 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.