Erosional landforms created by glaciers result from the powerful erosive action of ice as it moves across the landscape. These landforms are characterized by their unique shapes and structures, which provide insight into the history and dynamics of glacial movement.
Cirques
Cirques are amphitheater-like valleys with steep walls, formed at the head of a glacier.
Formation Process:
- Accumulation Zone: Snow and ice accumulate in a depression or hollow, often on the leeward side of a mountain.
- Erosion: The rotational movement of the glacier, along with freeze-thaw cycles and plucking, deepens and enlarges the hollow into a bowl-shaped depression.
- Headwall: Steep headwalls are formed as the glacier erodes the rock face.
Examples:
- Kareri Lake, India: Located in the Dhauladhar range of the Himalayas, Kareri Lake is a cirque lake formed by glacial erosion.
- Glendalough, Ireland: The Upper Lake in Glendalough is situated in a classic glacial cirque.
Horns
Horns are sharp, pyramid-shaped peaks formed by the headward erosion of several cirques converging on a single point.
Formation Process:
- Multiple Cirques: Cirques erode the sides of a mountain from different directions.
- Sharpening: Continued glacial erosion sharpens the peak into a distinctive horn shape.
Examples:
- The Matterhorn, Switzerland: One of the most famous examples of a glacial horn, formed by the convergence of several glacial cirques.
- Mount Assiniboine, Canada: Another iconic horn-shaped peak formed by glacial erosion.
Arêtes
Arêtes are narrow, knife-edge ridges formed between two adjacent glacial valleys or cirques.
Formation Process:
- Cirque Formation: Two glaciers erode parallel valleys or cirques.
- Ridge Creation: The glaciers erode the sides of the ridges between them, sharpening the ridge into a narrow arête.
Examples:
- Striding Edge, England: A famous arête in the Lake District, formed between two glacial valleys.
- Garden Wall, Glacier National Park, USA: An arête that provides a dramatic view and is a remnant of glacial erosion.
Glacial Valleys
Glacial Valleys (also known as U-shaped valleys) are valleys with a characteristic U-shape, steep walls, and a flat bottom.
Formation Process:
- River Valley: Originally, a V-shaped river valley exists.
- Glacial Erosion: As a glacier moves through the valley, it erodes the valley floor and sides uniformly, transforming it into a U-shaped profile.
Examples:
- Yosemite Valley, USA: A classic U-shaped valley formed by glacial activity in the Sierra Nevada.
- Kashmir Valley, India: A U-shaped valley formed by the movement of glaciers in the Himalayas.
Fjords
Fjords are deep, glacially carved valleys that have been inundated by the sea.
Formation Process:
- Glacial Carving: Glaciers carve deep valleys below sea level as they advance.
- Sea Inundation: After the glaciers retreat, seawater floods the valley, creating a fjord.
Examples:
- Sognefjord, Norway: One of the longest and deepest fjords in the world, carved by glaciers during the last Ice Age.
- Milford Sound, New Zealand: A famous fjord formed by glacial erosion, located in Fiordland National Park.
Additional Erosional Landforms
Hanging Valleys:
- Description: Smaller glacial valleys that join a main valley at a higher elevation, often leading to waterfalls.
- Formation Process: Formed when tributary glaciers erode their valleys less deeply than the main glacier, leaving them “hanging” above the main valley.
- Example: Yosemite Falls, USA: The falls descend from a hanging valley into the main Yosemite Valley.
Roche Moutonnée:
- Description: A rock formation created by glacial abrasion and plucking, with a smooth, gently sloping side and a rough, steep side.
- Formation Process: Formed as a glacier moves over bedrock, smoothing the up-glacier side and plucking rock from the down-glacier side.
- Example: Roche Moutonnée in the Alps: Common features in glaciated regions of the Alps.
Summary
Erosional landforms created by glaciers are diverse and dramatic, resulting from the immense power of ice as it moves and reshapes the landscape. Cirques, horns, arêtes, glacial valleys, and fjords each provide unique insights into the processes of glacial erosion and the climatic conditions of the past. These landforms are found in glaciated regions worldwide, from the Himalayas to the Alps, and from North America to New Zealand, showcasing the global impact of glacial activity on Earth’s topography.
