9 glacial depositional features

9 glacial depositional features




Glacial depositional features are features resulting from deposition of materials made by valley glacier or ice sheets. The material can be deposited by moving ice or by water from melted ice. 

The following are glacial depositional features

Till

this is material deposited directly by the glacier. till is always unsorted since glacier is not capable of doing so.

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Stratified drift

These are sediments laid down by glacial meltwater.

The main difference between till and stratified drift is that ice cannot sort the sediments it carries hence till is composed of unsorted particle sizes.

Stratified drift is sorted according to the size and weight of fragments




Erratics

these are large boulders or rock which has been carried by glaciers and deposited in the area where it does not belong. For example, it would mean the large boulder of limestone being deposited in an area where the bedrock is made up of granite.

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moraine

The most widespread features of glacier deposition are moraines. moraines are basically ridges of till, there are four main types of moraines.

End moraine and ground moraine are common in both Alpine glaciers and ice sheet.

End moraine forms at the terminal of the glacier. As the glacier begins to recede, the layer of till is laid down, forming a gently undulating surface of the ground moraine.




Alpine or valley glacier also forms two other types of moraines.

The sides of the valley glacier accumulate a large quantity of debris from the valley walls. When the glacier melts these materials are left behind as ridges called lateral moraines.

When two advancing valley glaciers come together to form a single flow, the till that once was carried along their edges is now joined to form medial moraine




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Eskers

these are deposits made by streams flowing in the tunnels underneath the ice, near the terminal of the glacier.

Drumlins

these are streamlined asymmetrical hills composed of till. The steep side faces the direction from which the glacier advances, while the sides point in the direction the ice moved.

It is thought drumlins are formed when glaciers advance over previously deposited materials.




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Outwash plain

it is a gently sloping area ( sometimes fan-shaped) comprising sands and gravels deposited by meltwater streams flowing from stationary margins of glacier or ice sheets.




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Kames

it is a small hill or poorly sorted sand and gravel that accumulates in the crevasses or in ice-caused indentations in the surface.

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Roche mountonnee

this is an asymmetrical hill of exposed bedrock; displaying gently sloping upstream side that has been smoothed and polished by a glacier and an abrupt steep downstream side