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).
- 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|
|Valley Glacier||Streams of flowing ice that are confined within steep walled valleys, often following the course of an ancient river valley|