Glacial Transport, Erosion, + Deposition

Define supraglacial transport:

Transport that occurs on top of the glacier.

Define englacial transport:

Transport that occurs within the glacier. 

Define subglacial transport:

Transport that occurs at the base of the glacier.

Define abrasion: 

The erosion of bedrock by scraping of the ice and debris within the ice.

What is the rate of abrasion affected by?

The rate of abrasion is controlled by the volume, shape, and hardness of rock fragments, as well as velocity of the basal ice and the presence of meltwater. 

Define plucking:

The removal and transport of rock from the bedrock. Occurs more in loose or well-jointed rock, where ice can infiltrate and fracture the bed.

Describe the formation + characteristics of a roche moutonnee:

An egg-shaped rock with a smooth gently sloped stoss side and steep fragmented lee side.  

 

As the ice flows over a more resistant rock, it erodes the top surface, striating it. As it flows over the lee side, it freezes to the surface, plucking fragments from it. 

Define an arete:

A narrow ridge between two valleys where two glaciers were side-by-side. An example is Striding Edge, in the Lake District.

Describe the form of a corrie:

It has a steep back and sides from erosion by the ice. The scooped base and lip occur due to rotational erosion by the glacier, as extensional flow out of the corrie reduces erosion at the lip.  

Describe the form of a glacial trough:

A u-shaped valley forms from the erosion of a glacier, as opposed to a v-shaped valley from a river. It will have steep sides and a flat base. 

Define a pyramidal peak:

Formed where at least 3 corries back onto each other, scooping out a pyramid-shaped peak in the mountain.

Define + describe till:

Material deposited by the glacier. 

 

It usually consists of clasts resting in a finer matrix, formed from a variety of materials (including erratics). It often has directionally oriented clasts. 

Define melt-out till:

Formed when the debris-rich basal layer melts. Often preserved best by hard rock cavities.

Define lodgement till:

Where slowing of the glacier dye to friction against hard bedrock allows till to be deposited. It is usually well oriented in the direction of ice flow.

Define deformation till:

Where you have a weak bedrock, till may deform along with the glacier (after it's been deposited).

Give the two types of end moraine:

• Melt-out (supra-glacial debris is deposited at the front of the glacier)

• Push (sub-glacial debris is pushed out the base of the snout.

Define a kettlehole:

Where a chunk of ice is buried below the glacier, then after retreating and melting forms a small pond in the landscape. If the ice reaches the water table, it will become permanent.