Goh Cheng Leong Chapter 6: Landforms of Glaciation YouTube Lecture Handouts

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Goh Cheng Leong Chapter 6: Landforms Made by Glaciation

Detailed lecture -

Glacial Landforms: 25 Erosional & 3 Depositional Features
Glacial Action, Process, Permafrost & 6 Periglacial Landforms

During Pleistocene period or Ice Ages (30,000 years ago) ice sheets covered temperate latitudes covering 12 million square miles – half of N. America, Europe, Greenland & high mountains of Eurasia

Now, major ice caps – Greenland (720,000 square miles) & Antarctica (5 million square miles)

Marie Byrd Land, Antarctica – ice cap was 14,000 feet thick

From central dome of ice cap, ice creeps in all directions as glaciers. Loftier mountains above surface as nunataks

Ice sheets reach to the sea – extend in polar waters and float as ice shelves. These break into blocks as icebergs (only 1 ⁄ 9th part is visible) . Diminish as comes close to warm waters.

Glaciation varies based on snowline (9,000 ft. for Alps and 17,000 ft. for Mt. Kilimanjaro)

Snow accumulation takes place – melt during day and refreezes at night [repeated to form hard granular mass as neve (French) & firn (German) ] . Due to gravity, neve brought towards valley below (beginning of flow of glacier or river of ice)

Glacier – broadest at source & tongue shaped. It is not liquid but with continued pressure, it moves. Movement is highest in middle where there is little obstruction. Side and bottom are held back by friction. Curves line – glacier moves faster at center.

Rate of movement of glacier

Alps – 3 ft. /day

Greenland – 50 ft. /day

Antarctica – few inches/day

Alestch Galcier in Bernese Oberland, Switzerland – 10 miles long (longest glacier in Europe) but smaller than those in Alaska & Himalayas

Piedmont Glacier – At foot of mountain ranges, they converge to form extensive ice masses. Example, Malaspina Glacier (65 miles long, 25 miles wide and 1,600 square miles)

Landforms of Highland Glaciation

Erosion in highlands and deposition in lowlands

Erosion by plucking (joints and beds drag them away) and abrasion (scratches the valley floor with frozen debris)

Larger fragments bear striation or scratching while finer material produce ground rock flour

Factors affecting rate of erosion

  • Velocity of flow
  • Gradient of slope
  • Weight of glacier
  • Temperature of ice
  • Geological structure of valley

Erosional Features

Corrie, Cirque (Scotland) or Cwm (Wales) – movement of glacier downslope produces shattering of upland slope & depression where fern or neve accumulates.

Deepens depression into steep, horse shoe shaped basin. At the base there is corrie lake or tarn

Erosional Features

Arete or Pyramidal Peak – 2 or more peaks join together to form pyramidal peak. Example, Striding Edge on Helvellyn in Westmorland or Matterhorn, Switzerland

Bergschrund (German) , Rimaye (French) – at head of glacier crack opens - as ice moves out in summer but no new snow to replace it. It acts as obstacle for climbers. On bends or slope, more crevasses are formed.

U – Shaped Trough – It wears away the sides as it moves, it scratches the rocks, removes debris and surface soil – has wide and flat floor. Floor is deepened and interlocking spurs are blunted to form truncated spurs. Loch Ness and Lake Ullswater as trough lakes or Finger Lakes. Finger Lakes lie in former river valleys carved into U-shaped trough.

Hanging Valleys – Main valley is eroded faster than tributary valleys. Ice form tributary hangs above main valley. Form head of water to generate HEP.

Rock Basins and Rock Steps – Glacier erodes the rock basin and rock basins filled by lakes are formed. Steep rocks due to different degree of resistance to glacial erosion and where tributary joins main valley additional weight of ice in main valley cuts deeper into valley floor to form steps

Moraines – rock pieces carried by glaciers – it can be lateral, end (terminal) or medial moraines. Where lower end of trough is drowned by sea it forms steep sided inlet as fjord (Norwegian and South Chilean Coast)

Medical, Lateral and Terminal Moraine

Landforms of Glaciated Lowlands

Depositional mainly brought by valley glaciers (leaves eroded material in restricted areas) and continental ice shelves

1 ⁄ 3rd of Europe and North America formed by Glacial and glacio-fluvial landforms

Roche Moutonnees – resistant residual hummock. Upstream smooth by abrasion and downstream rough by plucking & is steeper. Resembles sheepskin – wig worn in France. Seen in both highland and lowland

Roche Moutonnees

Crag & Tail – made of hardrock with steep slope on upstream & protects soft leeward slope from being worn away by ice. Example, Castle rock in Edinburgh, Scotland

Crag & Tail

Boulder Clay & Glacial Till – Unsorted glacial deposits spreading into sheets and not mounds forming featureless and monotonous landform. Example, East Anglia and Northern Mid-West USA

Erratics – boulders transported by ice that came with advancing sheets of ice but when ice melted, they were left stranded. They are made of different material than that region. Perched block is a large block of local or far-travelled rock which has been left by a melting glacier on top of a moraine or roche moutonnée. Example, Pennines

Drumlins – Oval, elongated whale back hummocks composed of boulder clay with elongation in direction of ice flow. Steeper at onset side and taper off at leeward end. Also known as baskets of egg topography. Example, County Down in North Ireland & around Great Plains in USA

Eskers – long, narrow sinuous ridge of porous sand and gravel which marks sites of sub-glacial melt-water streams. Example, Maine, USA eskers of around 100 miles seen, Punkaharju Esker in Finland. Since made of porous sand it cannot support trees (but in Finland form tree-covered ridge between lakes)

Terminal Moraines – Example, Baltic Heights in North European Plain

Outwash Plains – fluvio-glacial deposits washed from terminal moraines by streams and channels of stagnant ice mass. Kames are small hillocks that might cover the plains. With continuous glacial melting, kame delta collapses onto the land surface forming “kame and kettle” topography.

Kame and Kettle

Impact on Human

  • In mountains of Scandinavia – top soils are removed leaving them bare of vegetation. Has thin soils incapable of agriculture
  • Animal migration type farming seen in transhumance
  • Sandy and gravel outwash plains in North Germany
  • Marshy boulder clay in Central Ireland
  • Barren ice-scoured surface of Canadian and Baltic Shields are infertile
  • Erratics in Canada obstruct farming
  • When lakes are eliminated, old glacial lake beds with rich alluvium support heavy cropping
  • Great Lakes of USA formed by glaciation act as waterways
  • Formation of natural routeways across mountain terrains – Hudson Mohawk Gap links interior with Atlantic Seaboard of USA
  • In areas of dominant drumlins, drainage is poor
  • In outwash plains, eskers and kames excavated to provide sand and gravel for construction. Purest sand to make moulds for metal castings.
  • Scandinavia, Switzerland and Canada – coal, stream and waterfall from hanging valleys used to harness HEP & in industries
  • Skiing, mountain climbing and sight-seeing

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