Glacial Depositional Landforms Types of moraine and drumlins

Processes of Glacial transport As well as eroding the rock over which it flows, a valley glacier is also capable of transporting large amounts of debris. Some of this may be derived from rockfalls on the valley side. It is then transported on the surface of the glacier (supraglacial debris) or buried within the ice (englacial) Material found at the base of the glacier is known as subglacial.

Transport of debris - supraglacial

Glacier sole The lower few metres of a glacier that contain debris picked up from the bed. Rhonegletscher, Swiss Alps. blue ice of the glacier sole bedrock with some loose debris deposited on it

Small parts of the glacier bed are visible inside an ice cave at the front of Rhone Glacier, Switzerland. The ice is moving from left to right. Glacier bed Bedrock, or debris, over which the glacier flows.

Subglacial debris Debris which has been released from ice at the base of a glacier. Individual stones usually show signs of rounding as a result of abrasion at the contact between ice and bedrock. Taylor Glacier, Victoria Land, Antarctica, showing the formation of subglacial debris (basal till) that has melted out from the dark striped basal ice layer

Different types of moraines Moraine is a type of landform which develops when the debris carried by a glacier is deposited.

Lateral moraine Lateral moraine Debris deposited along the side of a glacier, comprising both rockfall debris from above and debris ground up by ice-marginal processes. A pair of lateral moraines Vadret da Tschierva, Grisons, Switzerland

Medial moraine Medial moraine Distinct ridge of debris occurring on the surface of a glacier where two streams of ice merge. Medial moraines on a tributary of the Kaskawulsh Glacier, Icefield Ranges, Yukon, Canada.

Terminal moraine Terminal moraine A prominent ridge of glacial debris formed when a glacier reached its maximum limit during a sustained advance. A massive terminal moraine marks the greatest advance of a glacier, during the last centuries, in Cordillera Huyhuash, Peru. A lake has formed between the terminal moraine and the glacier front.

Recessional moraine Recessional moraine Ridge of debris representing a stationary phase during otherwise general retreat. Recessional moraines deposited in the 1920s by Steigletscher, Bernese Alps, Switzerland act as a dam for the lake in the centre of the photo.

Push moraine A complex landform ranging from a few metres to tens of metres in height comprising assorted debris that has been pushed up by a glacier during an advance. Push moraine in front of Thompson Glacier, Axel Heiberg Island, Canadian Arctic.

Summary It is possible to recognise 5 types of moraine Lateral moraine Lateral moraine Medial moraine Medial moraine Terminal moraine Terminal moraine Recessional moraine Recessional moraine Push moraine Push moraine

Erratic A boulder or large block of bedrock that is being, or has been, transported away from its source by a glacier Huge erratics near Bremgarten, Canton Aargau, Switzerland which were deposited during the last glaciation

Till Till A poorly sorted mixture of mud, sand and gravel-sized material deposited directly from glacier ice. Basal till from the last major glaciation in Britain, c. 18,000 years ago; north shore of Loch Torridon, NW Scotland.

Erratics Moraines Drumlins

Direction ( o ) Number of stones The rose diagram shows the orientation between 0º and 210º of the long axes of stones obtained from a sample of till. The table shows some of the remaining orientations.

Drumlin A streamlined hillock, commonly elongated parallel to the former ice flow direction, composed of glacial debris, and sometimes having a bedrock core; formed beneath an actively flowing glacier. Group of drumlins near Hirzel Pass, Swiss Plateau

Crag-and-tail Crag-and-tail - A glacially eroded rocky hill with a tail of till formed down-glacier of it. Hohentwiel, a volcanic neck on the outskirts of Singen, southern Germany. Ice flow was from right to left