Geomorphology

Topography created by glaciers

Introduction to glaciers

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1 Introduction to glaciers

1.1 Types of Glaciers:

1.2 1. U-Shaped Valleys:

1.3 2. Cirques:

1.4 3. Arêtes:

1.5 4. Horns:

1.6 6. Fjords:

2 Depositional topography created by glaciers

2.1 1. Moraines

2.2 2. Drumlins

2.3 5. Kames

A glacier is a large, persistent mass of ice that forms from the accumulation and compaction of snow over long periods of time. These frozen rivers of ice can be found in mountainous regions and polar areas, where cold temperatures allow snow to accumulate faster than it melts. Glaciers play a crucial role in shaping the landscape, eroding rock, and carving out valleys. Due to the fact that temperature and precipitation patterns can affect their size and movement, they also store a significant amount of freshwater and are crucial indicators of climate change.

Types of Glaciers:

1. Alpine Glaciers:

Alpine glaciers, also known as mountain or valley glaciers, are found in high mountain valleys, flowing downhill through the landscape. They carve the terrain into sharp peaks and steep valleys as they move.

2. Continental Glaciers:

Continental glaciers are vast ice sheets that cover large land areas, particularly in polar regions like Antarctica and Greenland. They are not confined to mountain valleys and can spread over thousands of square kilometers, significantly shaping the underlying topography.

3. Piedmont Glaciers:

Piedmont glaciers occur when steep valley glaciers spill out onto relatively flat plains, spreading out in a bulb-like shape. They are often found at the base of mountain ranges.

4. Hanging Glaciers

Hanging glaciers are sections of ice that cling to steep mountainsides, often feeding larger glaciers below but not reaching the valley floor themselves, creating a distinctive appearance as if “hanging” on the slopes.

5. Cirque Glaciers

Cirque glaciers are small, bowl-shaped glaciers that form within cirques, which are hollows on the side of mountains. They contribute to the deepening and widening of these cirques through their erosional force.

6. Ice Caps:

Ice caps are miniature ice sheets covering less than 50,000 square kilometers. They mostly form in polar and subpolar regions but are not topographically limited, covering the landscape with a dome of ice.

Erosional topography created by glaciers

1. U-Shaped Valleys:

U-Shaped valleys are formed by the erosive action of glaciers as they slide down mountainous regions. Unlike the V-shaped valleys formed by rivers, the glacier widens and deepens the valley floor and sides, creating a broad, flat bottom and steep sides, resembling the shape of a ‘U’. This distinctive topography is a clear indicator of past glacial activity.

2. Cirques:

Cirques are bowl-shaped, amphitheater-like depressions that glaciers carve into mountains and highlands. They typically reside at the top of a glacial valley that has formed as a result of the erosive action of ice and water as the glacier moves and accumulates. The back wall is steep and often overhanging, while the floor is concave, leading down from the open side of the bowl. After the glacier retreats, these cirques may contain small lakes, known as tarns, formed by melting glacial ice.

The key parts of cirques include the headwall (steep, back wall), sidewalls, and a basin or floor that may hold a tarn (a small lake) after the glacier has melted. These components create the bowl-like shape characteristic of cirques.

3. Arêtes:

Arêtes are sharp ridges that form between two adjacent cirques or glacial valleys. As glaciers erode the sides of mountains, the intersecting point of two glaciers erodes more aggressively, creating a narrow, knife-edge ridge. These dramatic landforms are emblematic of glacially sculpted terrain, often extending like spines along the mountain.

4. Horns:

Horns are sharp, pyramid-like peaks that form when several cirques or glaciers erode a mountain from different sides. The most famous example is the Matterhorn in the Swiss Alps. As the glaciers retreat, they leave behind these prominent, pointed peaks, sculpted and sharpened by the erosive forces of ice on all sides.

5. Hanging Valleys:

Hanging valleys are formed when a main glacier cuts off a tributary glacier, creating an elevated valley with one end significantly higher than the other. These valleys are left hanging above the main valley floor, often leading to dramatic waterfalls as streams from the hanging valley drop to the lower level of the main valley. They are a common feature in glacial regions, indicating areas where smaller glaciers flowed into a larger valley glacier.

6. Fjords:

Fjords are deep, narrow, and elongated sea inlets carved by the movement of glaciers. They are formed when a glacier retreats after carving its typical U-shaped valley and the sea fills in the valley floor, creating steep-sided inlets often with dramatic cliffs. Fjords are typically found in locations with current or recent glacial activity and steep topography near the coast.

7. Glacial Striations:

Glacial striations are long, deep scratches or grooves left in bedrock by rocks and debris embedded in the bottom and sides of moving glaciers. As the glacier flows, this material acts like sandpaper, grinding and scratching the rock surface beneath. These striations are valuable to scientists, as they reveal the direction of glacier movement and the nature of the landscape over which it traveled.

Depositional topography created by glaciers

1. Moraines

Moraines are clumps of dirt and rocks that have accumulated on the glacier’s surface or that the glacier has pushed along as it moves. These materials are then deposited as the glacier recedes, forming various types of moraines, such as lateral, medial, terminal, and ground moraines, each with a unique formation and location relative to the glacier’s path. These features are often seen as ridges or mounds on the landscape and are significant indicators of past glacial movement.

2. Drumlins

Drumlins are smooth, elongated, teardrop-shaped hills of glacial deposits. They usually appear in groups, known as drumlin fields, indicating the direction of ice movement. The tapered end points to the glacier’s movement direction. Drumlins are formed beneath glaciers as they move over and reshape accumulations of till or older drift.

3. Eskers

Eskers are long, winding ridges of sand and gravel that form within or under glaciers. As a glacier melts, streams flowing within or beneath it deposit sediment, resulting in their creation. These ridges can be several kilometers long and stand out in the landscape after the ice has retreated. Eskers often appear as narrow, winding, elevated tracks of land.

4. Outwash Plains:

Outwash plains are broad expanses of flat land composed of sediments like sand and gravel, deposited by meltwater flowing from a melting glacier. Rivers and streams carry this sediment away from the glacier, forming a plain of sorted material in front of or beyond the glacier’s edge. These plains are often characterized by their smooth, flat surfaces and can cover extensive areas.

5. Kames

Kames are small, rounded hills or mounds composed of sand and gravel, deposited by meltwater pouring off the glacier into depressions or areas of ice stagnation. They represent the remnants of sediment accumulation once resting on or within the ice.

6. Kettle Lakes:

Kettle lakes are depressions or holes left in an outwash plain or other glacial deposit. They are formed by large blocks of ice that are buried in glacial drift and then melt, leaving behind a hole that fills with water. These lakes are often irregularly shaped and can be found in groups in areas that were heavily glaciated.

Topography created by glaciers