Glacial Deposition

Why does it occur?

1) Direct (or ice contact)- during deglaciation/frictional resistance to flow is high

2) Glacial Meltwater streams

Moraine is one product of deposition. Moraine is defined as lines of loose rock fragments which have been weathered from the valley sides above the ice, and have fallen downslope onto the ice.

Types of Moraine:

1) Supraglacial (surface moraines)

2) Englacial (debris carried within the glacier)

3) Subglacial (basal moraine)

4) Lateral (debris deposited alongside the glacier)

5) Medial (debris deposited between two glaciers)

6) Terminal (debris deposited at the end of a glacier)

Factors affecting moraine;

1) The amount of material carried by the ice 

2) The rate of ice movement

3) The rate of ablation and thus the amount of meltwater

A general term for glacial deposits is 'till' which is sometimes written as 'drift' on some maps. There are two types:

1) Ablation (left in situ)

2) Lodgement (left in lines in the direction of flow)

Words to use when describing till;

Unstratified

Unrounded

Unsorted

Unconsolidated

Landforms:

1.Erratics:

Large boulders foreign to the local geology that have been dumped by the ice, usually on flat areas (can be left stranded in precarious positions as perched blocks).

2.Drumlins:

Where a valley glacier flows into a lowland plain (causing a thinning of ice), the till has been deposited as small, oval mounds.