World Geography:Landforms of Glaciation

Today, only 2 major ice caps are present in this world – Antarctica & Greenland, along with many highlands above the snowline surviving in the world.

• The peaks of the loftiest mountains projecting above the ice surface are known as Nunataks
• Ice from ice cap creeps out in all directions to escape as glaciers
• When the ice sheets reaches down to the sea they float as ice shelves in polar waters.
• When ice sheets breaks into individual blocks, these are called icebergs.
• While afloat in the sea, only 1/9th of the iceberg’s mass is visible above the surface.

• They diminish in size when reaching warm waters & eventually melted, dropping the rock debris that was frozen inside them on the sea bed.
• Permanent snowfield is sustained by heavy snowfall in winters & ineffective snow melting & evaporation in summers as part of snow that melt during the day is refrozen during the night.
• This refreezing process repeats until it forms a hard, granular substance known as neve or firn.
• Owing to the gravitational forces, neve of the upland snowfield is drawn towards the valley below, which marks the beginning of the flow of glacier (river of ice).

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Glaciers

• Glaciers normally assume the shape of a tongue, broadest at the source & becoming narrower downhill.
• Though glacier is not liquid, but it moves gradually under the continual pressure from the snow accumulated above.
• Rate of movement is greatest in the middle where there is little obstruction
• The sides & bottom are held back by the frictions due to valley sides & valley floors.
• If a row of stakes is planted across a glacier in a straight line, they will eventually take a curved shape down the valley, showing that glacier moves faster at the centre than at sides.

Types of Glaciers

Piedmont Glacier	At the foot of the mountain ranges, several glaciers may converge to form an extensive ice mass
Cirque Glacier	Formed in a cirque, a bowl-shaped depression on the side of or near mountains Snow and ice accumulation in corries often occurs as the result of avalanching from higher surrounding slopes
Valley Glacier	Streams of flowing ice that are confined within steep walled valleys, often following the course of an ancient river valley