Depositional Features

Transportation & Deposition Due to weathering and erosion, there is a huge amount of debris around the glacier. Like with a river, this is moved or transported when the glacier has sufficient energy When the energy reduces, the glacier deposits material. This may occur when the ice meets resistant material, becomes overloaded with material, or the glacier retreats.

Transportation Material can be carried…. - On the surface (Supraglacial) mainly from rock falls - Within the body of ice (Englacial) - On the bottom of the glacier (sub-glacial)

Deposition Any material deposited directly by the ice is known as Boulder Clay or Till. Till is an unsorted mix of rock, clay and sand. The individual rocks are usual angular unlike river deposits.

Deposition Erratic – Rock that does not fit with the local geology in size or rock type. An example of a glacial erratic would be finding a piece of granite in a bed of limestone

Moraines Moraine refers to any glacially formed accumulation of unconsolidated debris which has been deposited by the ice. This debris may have been plucked off the valley floor as a glacier advanced or fallen off the valley walls as a result of frost shattering. Moraines may be composed of silt like glacial flour to large boulders. The debris is typically angular.

Which Moraine? Lateral Medial Complete the crossword to find the names of the different types of moraine. Now label on your diagram…(Think of the name to find the location) Terminal, Medial, Lateral, Recessional, Ground Recessional Ground Terminal

Ground Moraine Ground moraine is till deposited over the valley floor. It has no obvious features and is to be found where the glacier ice meets the rock underneath the glacier. It is left in situ when the glacier melts and retreats.

Lateral Moraine Lateral moraine forms along the edges of the glacier. Material from the valley walls is broken up by frost shattering and falls onto the ice surface. It is then carried along the sides of the glacier. When the ice melts it forms a ridge of material along the valley side.

Medial Moraine Medial moraine is formed from two lateral moraines. When two glaciers merge, the two edges that meet form the centre line of the new glacier. In consequence two lateral moraines find themselves in the middle of the glacier forming a line of material on the glacier surface.

Terminal Moraine The terminal moraine forms at the snout of the glacier. It marks the furthest extent of the ice, and forms across the valley floor. It resembles a large mound of debris, and is usually the feature that marks the end of unsorted deposits and the start of fluvially sorted material.

Recessional & Push Moraine Recessional moraines form at the end of the glacier so they are found across the valley, not along it. They form where a retreating glacier remained stationary for sufficient time to produce a mound of material. The process of formation is the same as for a terminal moraine, but they occur where the retreating ice paused rather than at the furthest extent of the ice. Push moraine is formed when a glacier has retreated, then advances again, pushing the already deposited material in front of it. They look identical to recessional moraine

Drumlins Complete a sketch of the drumlin. Direction of Ice Flow Label the key features Add the labels that just appeared How do drumlins differ from Roche moutonnées? Direction of Ice Flow Lee End Stoss End 50m Up to 1000m

Drumlins For some reason, the glacier loses energy and deposits material This may be confounded by the ice coming up against a obstruction in the ground (huge rock, harder band) The ice carried debris begins to deposit behind the obstruction. As the ice is still moving, it pushes this material over the obstruction and smoothes it into the drumlin shape This is only a theory, and if true, the drumlin should have a hard rock inside it at the highest point Drumlins are often found in swarms