The Mighty and Majestic “Glaciers”
Glaciers are colossal chunks of ice that can occupy an area of at least 10km2 and heights of at least 10 feet. These glaciers are formed in places where the amount of snow that freezes during winter is more than the amount of snow that melts during summer, accumulating over centuries. Most glaciers are as big as countries. Glaciers are the largest known moving objects on earth. The very presence of glaciers can alter the topography of the area. The pressure exerted by these massive blocks of ice can leave impressions on land. They can form deep trenches which in turn form water bodies, they can dam the rivers forming lakes, they sometimes form on top of dormant volcanoes which when activated cause floods, and they can even grind stone. These days, increasing global warming is causing the glaciers to melt which is leading to the rise in water levels of oceans which are slowly eating away small islands. Let us look into the details of the formation, traits and their geographical and geological effects of glaciers.
A “cool” fact: The land that you walk on today has most probably been shaped by the glaciers which existed during the ice age.
Formation of Glaciers
As discussed earlier, a glacier is formed in places where the melting of snow in summers is less than the freezing of snow in winters, which in turn causes accumulation of layers of snow. Places where such conditions are favourable are either north or south poles and at high altitudes where the atmosphere is thin and temperature mostly below the freezing point.
During the birth of the glacier, the first layer of snow which lasts through the entire summer is formed. This first layer of snow is called the “neve”. During the next year, a new layer of snow is formed on top of the neve. The top layer of snow exerts a certain amount of pressure on the first layer which causes the crystals of snow to compress and eventually solidify into ice as the pressure increases as the snow keeps piling up over the years. As the layers increase, the crystals get compressed even more and harden to a greater extent at the bottom. As the ice compresses, the air is pushed out causing an increase in the weight of the glacier.
- As the glacier forms into a colossal block, its weight becomes so high that at a certain point, it starts spreading out. This movement of the glacier is known as “Spreading”.
- Another way that a glacier can move is when it forms on an inclined surface. The friction between the ground and the base of the glacier causes melting at the bottom layer which forms a slippery layer at the bottom. This mode of movement is known as “Basal Slip”.
The propagation of a glacier may take place through either of the above modes or the combination of both.
Anatomy of a Glacier
The formation of a glacier occurs slowly through the years by compression of snow. The compression of the snow will not be even throughout the glacier. This will lead to an uneven distribution of temperature. The colder part of the glacier where the snow keeps collecting is called the “accumulation area”. The region which meets the surface of the land or ocean is relatively warmer and causes “Basal Slip”, is called the “Ablation” part. Glaciers present near the oceans are under constant force by the tidal waves. This causes chunks of ice to break off into the ocean. These chunks remain afloat on the oceans and are called “Icebergs”. This process is called “Calving”.
Types of Glaciers
Depending on region of formation and temperature of the surroundings, glaciers are classified as:
Alpine Glaciers – These type of glaciers form at high altitudes, generally on mountain tops. When the temperature rises, the ice melts causing fresh water to flow down (called “Melt Water Streams”). This water is fresh and clean. One of the examples can be found on our very own Himalayan Mountain ranges.
Sheet Glaciers – These types of glaciers are enormous in size form in colder areas and occur less frequently. One of the sheet glaciers in our world is present on the continent of Antarctica and another on Greenland. You can just imagine the size of these glaciers when we learn that the sheet glacier which covers Antarctica is six million cubic miles in volume.
Glaciers: The Mighty
The power and influence of glaciers is so large that it can actually change the shape of a planet. In geography class in school, we learn that the earth is not perfectly spherical but slightly flat at the poles. Well, now you can learn that this is because of the glaciers. The weight of the Antarctic glacier is so large that it actually presses down on the earth’s crust at the poles, making it flatter. The North Pole is also pressed down but not to the extent of the South Pole.Therefore the South Pole is slightly flatter than the North Pole.
One more feature of the glaciers is that they have the required force to crush rocks. The rocks get trapped in the glaciers by repeated melting and freezing in the ablation area of the glacier. The stone is compressed so much that it is ground to a fine powder called “Rock flour”. Glaciers tend to leave impressions wherever they pass through. They can widen valleys and deepen the lakes.
Preservation of Glaciers
For many millions of years after the meteor had struck earth, extinguishing the dinosaurs, there was a cooling down period on earth in which the entire earth was covered with sheets glaciers. But gradually as volcanoes began to release carbon dioxide, the ice melted away which finally revealed the land below. This period is referred to as the “Ice Age”.
Interesting fact: We are still living in the ending stages of the ice age. The glacial remnants of Antarctica and Greenland and other alpine glaciers are the evidence to prove this fact.
As mentioned earlier the emission of carbon dioxide into the atmosphere by volcanoes caused the ice to melt. This brings us to our next point “Global Warming”. Global warming is the rise in natural temperature of a region by emission of carbon dioxide into the atmosphere by human or natural anomalies. As the pollution is increasing, the rising global warming is causing the glaciers to melt. This causes a drastic rise in the sea level causing dangerous floods and icebergs. If the current ice content of the earth were to melt, the mean sea level will increase by 200m which would lead to devastating outcomes.