Glacial Landforms Created by Deposition

This section explains how glacial landforms are created by deposition. As glaciers move, they transport vast amounts of material, ranging from fine sediments to large boulders. When a glacier melts, it deposits this material, known as glacial till or boulder clay, across the landscape. These deposits create a range of distinctive landforms, including erratics and drumlins.

Erratics

• Erratics are large rocks or boulders that have been transported and deposited by a glacier in an area where the rock type does not match the local geology.
• This indicates that erratics can be carried long distances from their original location.
• For example, large granite erratics from Scotland can be found in the Midlands of England, having been transported by ice sheets during the last Ice Age.

Drumlins

• Drumlins are elongated, egg-shaped mounds of deposited moraine (glacial debris).
• They can range in size, from a few metres to over 50 metres in height and up to a kilometre in length.
• Drumlins have a steep stoss end, which faces the direction from which the glacier advanced, and a gentler lee slope, which shows the direction in which the glacier moved.
• They often appear in groups, forming a landscape described as a ‘basket of eggs’ topography.
• Large fields of drumlins can be found in areas such as County Mayo in Ireland and the Vale of Eden in Cumbria, England.

Formation of Drumlins

Drumlins form when a glacier loses energy and deposits its moraine. There are several theories about their formation:

Some suggest that drumlins are shaped by the movement of ice over deposited material, moulding it into an elongated shape.

Others believe they form when deposition occurs around an obstacle in the glacier’s path.

It is also possible that variations in ice movement and pressure cause certain areas to experience more deposition than others, leading to drumlin formation.

Glacial deposition is responsible for shaping many lowland landscapes, leaving behind features that provide clues about past ice movement and the powerful forces of glaciation.