Glacial Erosion

Glacial erosion is the movement of sediments carried by glaciers. These sediments move and scrape rocks creating new landforms and changing landscapes.

What is Glacial Erosion?

Glaciers move from basins and steep mountain valleys.
Ice in the form of glaciers can erode the earth’s surface and create landforms.
As glaciers move across the land (usually downhill on mountains and slopes.) They carry everything in their path (eg. grains of sand, huge boulders).
Debris that glaciers carry scrape along the surface eroding the material and the ground.
During Glacial erosion, there is Scraping of rocks and soil.
Eroded sediments are called moraine (mass of debris carried down by the glacier that can be seen on and around glaciers).

A Brief History

During the ice ages, glaciers covered various parts of the northern hemisphere.
Various landscapes such as northern North America and Europe have been shaped due to glacial erosion during the ice ages.
Today, glaciers exist in various places such as Greenland and Antarctica and continue to erode the Earth.

Types of Glacial Erosion

Glaciers cause erosion in 2 main ways:

Plucking: Plucking is a process in which rocks and various other sediments are carried by glaciers. They freeze on the bottom of the glacier and are carried away by the flowing ice. (Movement of rocks and sediments)
Abrasion: Abrasion is the process in which debris frozen along the glaciers scrape the rock beneath. The sediment and rocks frozen on the bottom of the glacier act like sandpaper wearing away rock leaving scratches and grooves known as glacial striations. Glacial striations show the direction of movement in glaciers.

Examples of Glacial Erosion

Finger Lakes in the united states (New York)
Carved long narrow deep inlets along the coast of Scandinavia
Erosion of Cape Cod Bay in Massachusetts
Fishhook shape of Cape Cod

What is the Impact of Glacial Erosion

Glaciers shear away mountainsides, creating deep valleys with vertical walls. (eg. Yosemite National Park)
Glacial erosion can form narrow valleys that are often U shaped with steep sides and rounded bottoms. Such valleys near coastlines can fill up with seawater to create fjord. (eg. Norway)
Glacial erosion can loosen rocks and soil, move sediments and create new landforms by the scraping and moving of rocks and various other debris.

Landforms Created by Glacial Erosion

Arêtes

Arêtes are jagged narrow ridges that are created when the walls of 2 glaciers meet. This leads to the erosion of both glaciers.

Cirques

Cirques are created when glaciers erode the mountainside creating hollows with steep faces. As the glaciers erode the mountain they form a tilted bowl-like hollow.

Horns

Horns are created when several Cirque glaciers erode the mountain until a steep pointed peek with sharp mountain ridges are created.

Trim Lines

When glaciers move along valleys they leave clear lines on the sides of mountains known as trim lines. The line is visible due to colour changes or changes in vegetation present on the rock.

Roche moutonnée

Roche moutonnée’s are created by the passing of glaciers resulting in symmetrical erosion forms. One side of the mountain is eroded by plucking and the other is by abrasion.

Hanging valley

A hanging valley is a valley that is cut across by a deeper valley or cliff. In other words, it is a valley that leads to another valley below.

Fun Fact

The Matterhorn in Switzerland displays 3 types of glacial erosions

Cirques
Arêtes
Horns