Glacial Erosion: How does Ice Change Landform?

Key Concepts

• Erosion
• Glaciers

Introduction: 

A glacier is a thick layer of ice that covers up a huge area of land. About 10% of the world’s land area is covered by glaciers. There are three conditions that affect the development of glaciers: temperature, location, and formation. Most glaciers form near the poles, i.e., the north and south poles, but glaciers also occur on mountains located at high elevations. These are locations with very low temperatures. 

Formation of glacier: 

Glaciers are formed from snow. It can take many years for a large glacier to form. Glaciers can only grow if the amount of snow that falls is more than the amount of snow that melts. If this ratio does not work properly, then glaciers will shrink instead of expanding. 

When temperatures are warm, the snow starts to melt. As the temperature goes down, the melted snow starts freezing. In perfect weather, when it starts snowing, the next layer of snow accumulates on the ice. Depending on the temperature, this new layer of snow also melts and freezes. This process becomes a cycle of snowing, melting, and freezing. When these layers of snow grow heavy, the constant process of melting(thawing) and freezing, and the weight, will convert the snow layers into an ice block. 

While the weight of all the snow layers pushes it down, the glacier will start to spread out, and gravity will pull it downwards. This causes the glaciers to cover more and more land. This spreading out of glaciers is nothing but glacial ice moving. As snow continues to fall, glaciers will continue to grow and spread, and so the process continues. 

The Earth goes through cooling cycles, which means that for considerable periods of time, there will be more snow falling on the Earth than melting. When the Earth enters these cooling cycles, snow falls faster on the ground than it can melt. This extra snow and lack of melting process cause glaciers to cover a huge surface of Earth with ice. 

The ice can change landforms. Most landforms take a long period of time to change. Running water, wind, waves, and ice change the landforms. These changes take place due to weathering, erosion, and deposition. 

How does ice change landform? 

When glaciers form, the bottom of the ice becomes fluid-like and starts flowing down the hill. Due to the weight of the glaciers, it moves slowly downhill by the force of gravity. The speed of movement of glaciers varies widely. Some glaciers move very slowly, like a few feet per year, whereas some glaciers may move a bit faster, like several feet per day. 

When glaciers move, they cover larger and larger areas over time and can change the land by creating very interesting landforms. When glaciers move, the ice present at the bottom and on the sides of a glacier freezes onto rocks. As glaciers move continuously, it causes the breakdown of rocks from the ground and sometimes even from the sides of a valley. The movement of the ice causes erosion of the land below the glacier. This is called glacial erosion or ice erosion. Glacial erosion is the shaping of the land present below the moving glacier. 

Processes of glacial erosion: 

The two important processes of glacial erosion are plucking and abrasion. 

Plucking: 

It is the erosion and transportation of pieces of rocks. In this process, glaciers expand over large areas of Earth’s surface; while going through this process, some ice melts, and water percolates into the cracks present in the rocks below the glacier. This water will undergo a snow cycle, i.e., freezing, melting, freezing, and so on. This cycle creates big cracks in the rocks, and slowly the rock breaks into pieces

Abrasion: 

It is erosion that occurs when broken rock particles rub against each other. The huge volume of the glacier, along with broken rock particles and sediments, generally rub and carve the surface of the rock present below the glacier. So, when glaciers move along with rock and sediment, it leaves behind scratch marks on the rock’s surface, giving the indication that once glaciers covered the land and formed various landforms. 

Various landforms formed by glacier erosion: 

U- shaped valleys (Glacial troughs): 

Glacial erosion converts the narrow and V-shaped valleys created by rivers and streams into U-shaped valleys by broadening the sides of the valleys and deepening the bottoms of the valleys. The small pieces of rock transported by the glaciers can be seen deposited throughout the bottom of the valley. 

Horn – When many glaciers erode the same mountain top, a pointed shape mountain peak is created, called a horn. 

Cirques: 

A bowl-shaped depression carved by glaciers into mountains and valleys with sidewalls at high elevations. 

Moraine: 

A moraine is a glacial depositional feature consisting of accumulated rocks, dirt, and other rubble that have been deposited by a glacier. 

Arête: 

It is a sharp-pointed rock formed between adjacent cirque glaciers. 

Summary

• Natural features on Earth’s surface are called landforms.
• There are three conditions that affect the development of glaciers: temperature, location, and formation
• A glacier is a thick layer of ice that covers up a huge area of land.
• B Glacial erosion is the shaping of the land present below the moving glacier.
• The two important processes of glacial erosion are plucking and abrasion.
• U-shaped valleys, horns, moraine, etc., are some of the landforms formed by glacier erosion.