(3) types of glacier and their formation/flows

• what is the name of the process that forms glaciers

  diagenesis
• explain the formation of glaciers


  each new fall of snow compresses and compacts the layer underneath, causing air to be expelled and converting low density snow into higher density ice
• what is an ice cap


  an area fewer than 50,000 square kilometres covered by ice
• what is an ice sheet


  a mass of glacial ice more than 50,000 square kilometres
• what is an ice shelf


  tongues of ice that extend from glaciers grounded on land
• what is a valley glacier


  streams of flowing ice that are confined within steep-walled valleys
• what is a piedmont glacier


  when valley glaciers spread out onto low-lying areas and merge to form a single ice mass
• what is a corrie


  an armchair shaped hollow found on the side of a mountain
• what is a niche glacier


  small patches of glacier ice found on upland slopes
• why do glaciers move in general

  a glacier is a pile of ice and therefore deforms under the force of gravity.
• why do glaciers move downslope

  they accumulate mass in their upper portions from precipitation and wind-blown snow and ablate in their lower portions
• why do glaciers move backwards


  a receding or shrinking glacier still flows (though very slowly), it just melts faster than it accumulates mass in its upper reaches. as a result, the glacier will get thinner and the snout position will recede backwards
• what are the two types of glacier temperatures

  warm and cold based
• features of warm based glaciers


  • rises above 0 degrees in summer, allowing surface melting
  • temperatures allow for some melting of ice
  • basal temperatures at or above pressure melting point
  • landforms of erosion and fluvioglacial origin
  • rapid rates of movement
  • high altitude location
  • steep relief
  • below the surface, pressure of ice allows melting
  • meltwater acts as a lubricant
  • greater erosive power
  • large volumes of ice transferred across the equilibrium line
• features of cold based glaciers

  • move slower
  • limited summer melting
  • no pressure melting
  • often froze to bedrock
  • less erosive power
  • high latitude locations
  • low relief
  • basal temperatures below pressure melting point, so movement is limited
• what are the three ways that glaciers can move

  • internal deformation
  • basal sliding
  • soft bed subglacial deformation
• explain internal deformation


  • response of ice grains to pressure
  • increased ice thickness/surface slope angle may cause more internal deformation
  • elongation of ice crystals and displacement of ice crystals relative to each other
  • movement along slip planes that form within and between ice grains
  • small-scale displacement translates into large-scale motion
  • sometimes, ice faulting occurs, resulting in separation and displacement of large blocks of ice
• what is extending flow


  when the gradient becomes steeper, velocity increases and ice becomes thinner as stretched
• what is compressing flow


  when the gradient is reduced, velocity reduces and ice catches up with ice in front, compression occurs and the ice thickens
• what is a crevasse


  a deep, v-shaped cleft in upper, brittle parts of the glacier due to ongoing extension, where ice is subjected to tension

  can get longitudinal crevasses where the glacier becomes wider
• what is a serac


  tower of unstable ice that forms between crevasses, commonly found in areas of accelerated flow
• explain basal sliding


  • warm based glaciers mainly move by basal sliding
  • glacier can slide across layers of meltwater as a lubricant
  • movement causes friction, which enhances melting
  • most effective on steep slopes
• what is regelation slip


  if the glacier bed is rough during basal sliding, this increases pressure melting and ice flow
• what is soft bed subglacial deformation


  as soft sediment flows below the glacier deforms and the ice sheet moves with it
• what is surging


  • rapid movement
  • occurs due to large levels of inputs or large amounts of meltwater
  • a short-lived phase of accelerated flow
  • glacier surface can be broken up into a maze of crevasses
• what is icefall


  a steep, heavily crevassed section of a glacier where it flows over a step in the bedrock
• what is rotational flow


  relates to the ice pivoting around a central point and moving in a circular way so that it deepens the area away from the lip