Introduction
A glacier is a large, perennial body of ice and snow that is deforming under its own weight, resulting in the transport of ice from higher to lower elevations. The body of ice and snow must be several tens of meters thick for this to take place. The movement of the ice always forms the upper part of the glacier towards the lower end, regardless of whether the glacier is advancing or retreating. Glaciers are also one of the most powerful forces shaping the earth's surface.They slice bedrock and are prime creators of sediments. They form distinctive shapes and landforms. Glacial episodes also took place hundreds of millions of years ago.
Glacier Distribution
Existing glaciers occupy 16 million sq km, roughly 10% of the earth’s surface. Out of that, 12.5 million sq km is located in Antarctica. The giant Antarctic ice sheet may be as much as 10 million years old. Part of it is 4 km thick. The weight of ice has depressed the surface of the continental lithosphere more than a km below sea level. Today, however, the land is slowly rising. It shows that in the past, the ice was much thicker than it is now. The second-largest ice sheet is the Greenland ice sheet, which covers about two million sq km. Other important ice sheets are in Iceland, Novaya Zemlya in the USSR, IceCaps in Canada and Alaska.
Modern Glaciers: The Different Types and Locations of Modern Glaciers
There are mainly three types of glaciers. They are called valley (Alpine) glaciers, piedmont glaciers, and continental glaciers as they increase in size. Valley Glaciers are located on the entire world’s mountains whose peaks lie above the snow line. They flow from a high altitude down the valley. Piedmont glaciers are formed by the flowing together of two or more valley glaciers. It is third-hand snow. Some piedmont glaciers are enormous. In Alaska, Malaspina Glacier is the product of several separate piedmonts that have joined together to cover a large area. The world's largest glacier today belongs to the category of continental glacier ice sheets. The glaciers flow outward in all directions, forming relatively smooth surfaces.
Some general curiosity about glaciers
Our country is also called a Himalayan country. About 17% of our country is covered by mountains. There are many tall and world-famous mountains, including Mt. Everest, which lies in the northern part of our country. Unfortunately, the people of our country do not know the fundamentals of mountains and glaciers. The glacier is a subject which is directly linked to us in different aspects. It is the pride of Nepalis and humankind. So, here are some frequently asked questions and their short answers are given. I hope that will help to understand the basic idea and process of the glacier.
Why does a glacier transport ice?
A glacier can be divided into an accumulation zone and an ablation zone. In the accumulation zone, in the upper part of the glacier, more snow falls than melts during the course of a year. The result is a net gain in the form of snow. In the ablation zone, in the lower part of the glacier, more ice and snow melts than accumulates during the course of the year. The result is a net loss of snow and ice. With the help of gravity, the lost ice in the ablation zone is replaced by ice from the accumulation zone through the transport of ice from the upper part to the lower part. The accumulation is determined by the deposition of snowfall, and snow and ice avalanches onto the glacial surface. The amount of ablation is determined by air temperature and solar radiation, which causes melting and evaporation. Accumulation normally increases with increasing altitude, while melting increases with decreasing altitude.
What is the mass balance?
The glacier mass balance is the difference between the total accumulation of snow on the glacier and the total ablation of ice and snow calculated over a year. The glacier mass balance can be positive, negative, or zero. If the accumulation is substantially higher than the ablation over a number of years, then the glacier will grow in mass. If the ablation is substantially larger than the accumulation over a number of years, the glacier will reduce its mass.
Why do glaciers grow and shrink?
A glacier is a form of frozen storage of water. For storage to be in equilibrium, the precipitation at the accumulation zone and the melting at the ablation zone should be equal. In other words, the mass balance is zero. The balance can be altered by varying the amount of snowfall (less or more) and the amount of ice/snow melting.
What is a moraine?
The glacier may also transport a loose mix of rock debris, including anything from boulders to sand clay, inside or on top of the ice. In the ablation zone, this debris becomes exposed at the surface as the ice melts. The debris layer becomes thicker towards the glacier's last stop. This debris will eventually be deposited as moraine along the side or front edge of the glacier, forming moraine ridges. A terminal marine ridge is formed when a glacier ends at about the same position over an extended period of time.
What factors affect the length of a glacier?
If the glacier mass is accumulating faster than it is melting, It will normally result in the glacier snout advancing. Similarly, if the glacier mass is accumulating lower than it is melting, then it will normally result in the glacier snout retreating. Some glaciers show so-called surging behavior. Such glaciers do not have a straight relationship between mass balance and snout position. They may have a stagnant position for many years, followed by a large and rapid advance, which is then followed by a retreat.This might lead to some glaciers advancing simply because more of the ice mass moves down slope without any change, or even with a reduction, in the total ice mass. The change is thought to be due to increased elasticity resulting from an increased internal temperature of the ice. The glacier then becomes longer but thinner.
Are glaciers good indicators of climate change?
Climate change includes rising or falling temperatures, which cause increased or decreased melting, as well as changes in the amount and timing of precipitation, which cause changes in the amount of accumulation.In general, changes in the position of the glacier snout are a good indicator of the mass balance and, thereby, of the climate. However, the snout position is only a general indicator. Fluctuation in a glacier terminus is an indirect, delayed, and filtered signal of climate change. Measurements of the mass balance, on the other hand, provide direct evidence of glacier volume increasing or decreasing with annual resolution. Mass balance data constitutes a direct and undelayed signal of climate change. Observation of a single glacier or group of glaciers in a single small region should not be used to make generalized statements about climate change.
Does glacial advance or glacial retreat mean that a glacier has more or less ice?
In general, change in the position of the glacier snout is a good indication of change taking place in the total amount of ice in the glacier, but the relationship ship is not direct. The position of the snout is only an indicator; it does not give exact information about changes in the amount of ice in the glacier.
What do the Himalayan glaciers tell us about climate change?
The overall changes in Himalayan glaciers, with the loss of small glaciers and the retreat of others, are consistent with an increase in the average temperatures and possibly changes in precipitation patterns. Observation of a single glacier (whether small or large) cannot be used to extrapolate any general statements on climate change as there are too many site-specific factors that can affect the behavior of a specific glacier. To draw a clear, scientifically justified conclusion about the changes that are occurring, it is critical to compare and summarize observations from a number of glaciers in different areas, sizes, and altitudes.Direct measurements of Himalayan glaciers are few and far between, and generally restricted to the more accessible glaciers. Remote observations from satellites only show approximate indicators like glacier length, and no comparative images are available of historical periods. A significantly increased level of scientific observation will be needed before changes in Himalayan glaciers can be accurately recorded and reliable predictions made. Statements based on individual glacier behavior may have contributed to recent contradictory interpretations that have appeared in the media.
Conclusion
A glacier is a form of frozen storage of water. They are one of the most powerful forces shaping the earth's surface. Existing world glaciers occupy 16 million sq km, roughly 10% of the earth’s surface. There are mainly three types of glaciers. They are called valley (Alpine) glaciers, piedmont glaciers, and continental glaciers as they increase in size. The glacier is an intriguing subject in and of itself, and understanding its behavior is even more intriguing and important to us.The northern parts of our country are occupied by alpine glaciers. Also, for this reason, we should be familiar with glaciers and the events caused by them. Scientists in the modern world have been concentrating on the topic of glaciers and their effect on climate change. It should study the past history and present condition of world glacier distribution to make a prediction of its effect on climate and human life.
Sudarshon sapkota
B.Sc First year
Reference:
G.B. Mahahapatra, A Textbook of Physical Geology, CBS publication.
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