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Glaciology

2007 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.
   Enlarge
   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 is the study of glaciers, or more generally the study of ice
   and natural phenomena that involve ice. The word glacier is derived
   from the Latin glaciees, meaning ice or frost.

   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 patterns, effects of glaciers on
   climate and vice versa, the dynamics of ice movement, the contributions
   of glaciers to erosion and geomorphology, and lifeforms that live in
   the ice. 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.
     * 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, where the sum of melting and evaporation (sublimation) is
       greater than the amount of snow added each year.

Movement

   Ablation
          wastage through evaporation and melting

   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.

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