How glaciers transport material over large distances

Glaciers are powerful agents of transportation, moving a variety of materials such as sand, clay, and rocks across vast distances. As they flow, they carry debris along their paths.

Methods of material transportation by glaciers

• Frozen within the ice - Material becomes embedded and frozen inside the glacier, carried along as the ice moves.
• Carried on the surface - Debris falls onto the glacier from surrounding slopes or is deposited by wind, resting on top as the glacier advances.
• Pushed ahead (bulldozing) - Rocks and sediment are shoved forward at the front of the glacier, accumulating as it progresses.

The nature of glacial deposits and till

When a glacier melts, the material it has been carrying is released and deposited onto the valley floor. These deposits have distinct characteristics that set them apart from other types of sediment.

Characteristics of glacial deposits

• Unsorted mixture called till - Glacial deposits, known as till, consist of an unsorted blend of materials of all sizes, from fine clay to large boulders.
• Lack of size sorting - Unlike river deposits, which are often sorted by size and weight, glacial deposits show no such organisation.
• Varied rock shapes and sizes - The till contains rocks of all shapes and sizes mixed together without any pattern.

Types of moraines formed by glacial deposition

Moraines are specific landforms created by the deposition of material carried by glaciers. They vary depending on where the material is deposited relative to the glacier's position.

Different forms of moraines

• Ground moraines - These form from eroded material dragged along the base of the glacier, spread over a wide area of the valley floor as the ice melts.
• Terminal moraines - Found at the snout, or end, of the glacier, these mark the furthest point the ice has reached. They appear as semicircular mounds when the glacier retreats.

Formation and characteristics of drumlins

Drumlins are distinctive elongated hills formed from till that has been transported and shaped by a glacier. They provide insight into the direction of past ice flow.

Process of drumlin formation

1. Material accumulates at the base of the glacier, having been eroded from other locations.
2. As the ice at the bottom melts, this material is deposited on the valley floor.
3. Over time, the deposited material builds up into small hills beneath the glacier.
4. Continued ice movement moulds these hills into their final streamlined shape.

Distinctive shape of drumlins

• Upstream end (stoss side) - Rounded, blunt, and steep, facing the direction from which the glacier came.
• Downstream end (lee side) - Tapered, pointed, and gently sloping, indicating the direction of ice flow.

Formation and features of crags and tails

Crags and tails are unique landforms resulting from the differential erosion and deposition around resistant and softer rock outcrops as a glacier passes over them.

Components and formation of crags and tails

• Crag formation - Composed of resistant rock, the crag is the first part to encounter the glacier (stoss side). The ice erodes material around it, leaving a steep, prominent hill.
• Tail formation - Made of softer rock sheltered behind the crag, the tail is protected from intense erosion. As the glacier moves past, the tail is shaped into a smooth, sloping incline.
• Depositional tails - In some cases, the tail forms from till deposited by the glacier after it passes the crag, which is then smoothed by the continuing ice flow.