Glacier: Definition, Types and Glaciated Areas

1 year ago

Atiqur Rahman

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A glacier is a creeping mass of ice. It moves very slowly. The immediate apparent movement of a glacier is difficult to perceive. It takes a longer time to see the movement. The movement happens under the influence of gravity in the downslope direction.

Since the glaciers are solid mass, they have an enormous capacity to erode the rock and transport the rock fragments. In this process, they sculpt significant features creating distinct landscapes.

Types of Glaciers

Mountain Glacier

The accumulation of ice over the mountain slope covering large areas is called a mountain glacier. It is the outward flow of ice from the ice fields encompassing several peaks of the surrounding areas. It is mostly narrow and long because it occupies the preexisting river valley.

At a higher altitude, the temperature is very low, but as long as it comes down, the temperature keeps on increasing. This leads to the ablation or breaking of glaciers into ice pieces and ultimately melting.

They have generally termed glaciers which are found in the mountains of tropical and temperate regions. Glaciers are also found in the mountains of the polar region, but generally, they are termed polar glaciers because they occupy a big continuous area of ice accumulation.

Valley Glacier

A Valley glacier is a narrow strip of ice accumulation confined within the two walls of the preexisting river valley. Valley glaciers are also found on the mountain slopes. Sometimes, both of them are used as synonyms, but they have a slight difference.

Mountain glaciers are huge in size, whereas the valley glaciers are small in size, and the ice is restricted within the two banks of the previously carved-out river valleys. The downside of terminating glaciers is tongue-shaped, i.e., smoothened round in appearance. Both of them are also known as Alpine glaciers.

In fact, Alpine glaciers originate from the mountain summits and descend through the mountain valleys. Valley glaciers are very short in comparison to continental glaciers. The longest of this type is less than 80km long (Table). The smallest may be a few hundred meters.

Five Longest Non-Polar Glaciers in the World

Rank	Name of the Glacier	Location	Length in km
1	Fedchenko Glacier	Tajikistan	77
2	Siachin Glacier	India	76
3	Biafo Glacier	India (POK)	67
4	Bruggen Glacier	Chile	66
5	Baltoro Glacier	India (POK)	63

Source

Piedmont Glacier

When the ice mass moving through the steep surface of the mountain reaches the foothills or the plain area, it creates a Piedmont glacier. Piedmont means an area from the foothills to the flat plain land. The confined ice of the valley glacier is forced to spread over a larger area because of the lowering of the slope. It takes the shape of bulb-like lobes (Figure).

Continental Glacier

A continuous sheet of ice occupying a very large area is known as a continental glacier. The movement of the continental glacier is normally from the centre to outward in all directions (Figure).

Relatively small-sized continental glaciers are known as ice fields. Similarly, an ice sheet is a big continental mass of glaciers covering an enormous area. Almost the whole of the Antarctic and Greenland is covered with ice sheets.

A thick mass of ice and snow (Figure) forming a glacier over a great deal of area is termed an ice cap. It may develop over the continental or on mountain glaciers.

Continental glaciers are very long and large in comparison to valley glaciers. The longest continental polar glacier is more than 500 km long (Table).

Five Longest Continental Polar Glaciers in the World

Rank	Name of the Glacier	Location	Length in Km
1	Lambert-Fisher Glacier	Antarctica	77
2	Novaya Zemlya Glacier	Russia	76
3	Artic Institute Glacier	Antarctica	67
4	Nimrod-Lennox-King Glacier	Antarctica	66
5	Denman Glacier	Antarctica	63

Source

Anatomy of Alpine or Valley Glaciers

Alpine glaciers are concerned with mountain glaciers found on different continents at varying altitudes.

The uppermost section is characterized by a zone of ice accumulation due to extreme cold conditions. Intermediaries are characterized by greater rock plucking from the glacial valley and abrasion (Figure). A steep slope is associated with cracks in ice blocks called crevasses.

A lowermost zone is accompanied by the melting of the ice due to an increase in temperature. This is known as the zone of ablation. In this zone, the load carried by the glacier is deposited, popularly known as moraine. Over the years, a sort of equilibrium of ice accumulation has been maintained.

Glaciated Areas in the World

Glaciers are found on all continents except Australia. Their widespread existence is in polar areas because of favourable conditions for ice accumulation.

Since the Arctic is an ocean around the North Pole, the amount of glacial ice is widely variable with changing seasons, but the ice survives throughout the year. The land parts in the periphery of the Arctic Ocean, like northern Canada, Alaska, Greenland and the northern Eurasian region, have sustaining glaciers. These land masses have glaciers throughout the year. The direction of the flow of ice is outward as per the slope of the area (Figure).

Almost the whole of the Antarctic continent is situated south of the Arctic Circle. Its 98 per cent area is covered with ice, and only 2 per cent of bare rocks are found. Antarctica has an ice sheet with an average thickness of about 2.16 Kilometers. The maximum thickness at Terre Adelie is recorded to be 4776 meters.

Almost half of the coastal fringe areas are free from ice. Huge icebergs float on the ocean waters, particularly in the summer season (November to February) in the southern hemisphere. About 80 per cent area of Greenland is under ice cover (Figure). The cross-section drawn on the maps of Greenland and the Antarctic has been drawn, and the thickness of the ice over them is clearly seen.

We know that the effect of temperature is progressively reduced with increasing altitudes. The highest air temperature recorded at sea level keeps declining with increasing height. The temperature distribution is also affected by the inclination of the sun’s rays. Due to this reason, the air temperature keeps on declining with increasing latitudes.

That is why the permanent snow line is different at different latitudes. Therefore, altitudes at various places where the ice cover is found differ with changing latitudes.

In Polar Regions, it is available at the ground level. It is found five kilometres above the mean sea level in the equatorial zone, whereas, in the temperate zone, it is one km to five kilometres (Figure).

In central Africa, at Kilimanjaro, it is found to be about 5500 meters; in the Himalayas, it is between 4500 to 6000 meters and in the Alps, it is 2800 meters above mean sea level. Therefore, glaciers are found at higher altitudes of the mountain ranges, even in the tropical and temperate regions of the world.

Height of Snowline at Different Latitudes

The entire frozen water of the globe is termed a cryosphere. The cryosphere consists of ice and snow occupying the earth’s surface, mountains, rivers, lakes and oceans. The total amount of water stored in the cryosphere is about two per cent of the total hydrosphere.

Out of the total area under the ice, 85.30 per cent is in Antarctica and 13.27 per cent in the Arctic region. Both constitute 98.57 per cent of the glaciated area of the globe. The rest of, about 1.5 per cent of the glaciated area is in other parts of the world. The details of the distribution of glaciers are given in the Table.

Area and Approximate Volume of Present-day Glaciation

Area/Region	Glaciated Area in km²	Glaciated Area in %	Volume of Ice km³	Volume of Ice in %
Antarctic	13,500,000	85.30	29,500,000	89.03
Arctic	2,100,000	13.27	3,200,000	9.66
Asia	114,000	0.72	220,000	0.66
North America	78,000	0.49	150,000	0.45
South America	25,000	0.16	48,000	0.14
Europe	9000	0.0569	16,000	0.05
New Zealand	1000	0.0063	1800	0.0054
Africa	25	0.0002	35	0.0001
New Guinea	15	0.00009	25	0.00008
Total	15,827,040	100.00	33,135,860	100.00

Source: Encyclopedia of Life Support System

Glacier: Definition, Types and Glaciated Areas