Geog A Level Notes on Periglaciation

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  • Created on: 27-11-12 07:03
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1. What does periglacial mean? Where are the main areas subject to periglacialtion today?
Periglacial describes the land adjacent to glacial areas. This land does not have glacial charactaritcs of
ice sheets or glaciers, but instead key landforms due to displacement of soil materials, migration of
groundwater, all created by intense frost action, and temperatures below 2C for a large part of the year.
According to certain definitions of periglacation, large areas in Siberia, Canada and Alaska and smaller
areas in Fennoscandia,Tibet, Iceland, Greenland, Antarctica and the Andes are periglaciated.
2. What are the main characteristics of periglacial areas?
Periglacial landforms can be subdivided into two main groups: slope landforms and
patterned ground landforms. Slope landforms include cryoplanation terraces, gelifluction
terraces, and cryopediments. These slope landforms are similar to slope landforms found in
other warmer, semiarid environments. Patterned ground landforms include thermokarsts,
pingos, palsas, earth hummocks, and polygonal ground. Most of the patterned ground landforms
are completely unique to the periglacial environment.
Coombe and head deposits Coombe deposits are chalk deposits found below chalk
escarpments in Southern England. Head deposits are more common below outcrops of granite
on Dartmoor.
Patterned Ground is stones which form circles, polygons and stripes. Local topography affects
which of these are expressed. A process called frost heaving is responsible for these features.
Solifluction lobes are formed when waterlogged soil slips down a slope due to gravity forming
U shaped lobes.
Blockfields or Felsenmeer are areas covered by large angular blocks, traditionally believed to
have been created by freezethaw action. A good example of a blockfield can be found in
the Snowdonia National Park, Wales. Blockfields are common in the unglaciated parts of the
Appalachian Mountains in the northeastern United States, such as at the River of
Rocks or Hickory Run Boulder Field, Lehigh County, Pennsylvania.

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What is permafrost and what are the different types? Outline their characteristics.
Get a map to show the distribution of permafrost in North America. Describe and
explain the distribution.
Permafrost is defined on the basis of temperature, as soil or rock that remains below 0°C throughout
the year, and forms when the ground cools sufficiently in winter to produce a frozen layer that persists
throughout the following summer. Permafrost underlies more than 50% of the ground surface of
Canada.…read more

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Isolated Patches. The only occurrence of Subsea Permafrost is a small area on the coast of
Northern Canada, nearing the Arctic Circle.
4. What is the active layer ­ what happens to this through the year? What is talik?
The active layer is the upper zone of soil in higher latitude locations that experiences daily
and seasonal freezethaw cycles.
An unfrozen section of ground found above, below, or within a layer of
discontinuous permafrost.…read more


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