Denudation - Glacier
Glaciers are large, thick ice masses formed on land when falling snow is compressed into ice over many centuries.
Glaciers grow when snow accumulation surpasses ablation over a long period of time, frequently millennia.
Glaciers as Geomorphological agents have an immense impact.
The force of gravity affects the movement of glaciers.
In contrast to the flow of water, glaciers move slowly.
What are glaciers?
Glaciers are huge ice masses that move under their own weight.
They are usually seen in snow-covered areas.
Glaciers encompass around 10% of the Earth’s geographical area and are the world’s greatest freshwater reserves.
Types of glaciers
1. Continental Glaciers
Continental glaciers are continuous masses of ice that are much larger than alpine glaciers.
There are no mountains or other features that surround these glaciers.
As a result, they tend to spread out and cover everything in their path.
When ice sheets spread out from the centre, they cover entire valleys, plains, and even mountain ranges with snow.
Some examples of continental glaciers are Antarctica, Iceland, Greenland, etc.
The ice caps are the snow and ice covers on mountain ranges that give rise to valley or mountain glaciers.
They can be found at lower elevations as well.
The area of the ice caps is less than 50,000 km square.
3. Piedmont Glaciers
At the foot of the mountains, the piedmont glaciers form a continuous sheet of ice.
A mass of ice that has moved downslope towards low-lying plains is referred to as a Piedmont Glacier.
It spreads out throughout the landscape, forming broad lobes of solid ice.
One of the most well-known instances of this type of glacier is Alaska’s Malaspina Glacier.
4. Valley Glaciers
A valley glacier is a glacier that fills a valley. Valley glaciers, also known as Alpine Glaciers, are located in valleys formed by high mountains such as the Himalayas in India.
Because of their long and narrow, ribbon-like shape, these glaciers are generally simple to spot.
The majority of valley glaciers originate in mountain glaciers and extend to gorges, basins, and, of course, valleys.
1. Glacial Valleys/Troughs
These valleys are trough-like and U-shaped with broad floors and relatively smooth, and steep sides.
The valleys may contain littered debris or debris shaped as moraines with a swampy appearance.
Very deep glacial troughs filled with seawater and making up shorelines (in high latitudes) are called fjords/fiords.
Often are found at the heads of glacial valleys, these are the most common of landforms in glaciated mountains.
They are deep, long, and wide troughs or basins with very steep concave to vertically dropping high walls at their head as well as sides.
A lake of water can be seen quite often within the cirques after the glacier disappears. Such lakes are called cirque lakes or tarn lakes.
1. Glacial Till
The unassorted coarse and fine debris dropped by the melting glaciers is called glacial till.
Some amount of rock debris small enough to be carried by such melt-water streams is washed down and deposited.
Such glaciofluvial deposits are called outwash deposits.
The outwash deposits are roughly stratified and assorted.
They are long ridges of deposits of glacial till.
Terminal moraines are long ridges of debris deposited at the end (toe) of the glaciers.
Lateral moraines form along the sides parallel to the glacial valleys.
Many valley glaciers retreating rapidly leave an irregular sheet of till over their valley floors called ground moraines.
The moraine in the centre of the glacial valley flanked by lateral moraines is called a medial moraine.
They are imperfectly formed as compared to lateral moraines. Sometimes medial moraines are indistinguishable from ground moraines.
These are ridges made of sands and gravels, deposited by glacial meltwater flowing through tunnels within and underneath glaciers, or through meltwater channels on top of glaciers.
Over time, the channel or tunnel gets filled up with sediments. As the ice retreats, the sediments are left behind as a ridge in the landscape.
They are smooth oval-shaped ridge-like features composed mainly of glacial till with some masses of gravel and sand.
The long axes of drumlins are parallel to the direction of ice movement.
They may measure up to 1 km in length and 30 m or so in height.
The drumlin end facing the glacier is called the stoss end and is blunter and steeper than the other end called tail.