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Flashcards in Glacial transportation and deposition Deck (22)
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What is supraglacial debris?

Debris that is carried on the surface of a glacier either as the sides of the ice, or as a medial moraine.
Normally derived from rockfalls.
Tends to be angular in character.


What is englacial debris?

Debris that is found in the main body of the glacier that has been covered from subsequent snow fall.


What is subglacial debris?

Moved along under the ice by subglacial melt water channels.
May include rock fragments that have fallen down crevasses and material eroded at the base.


What is a till?

Valleys covered by deposition.
Transported as supraglacial or englacial debris.
Ice melts - deposition.
Unsorted mixture of clay and rocks.
Individual rocks tend to be angular/sub-angular.


What is an example of a till?

Till of South Lancashire.
Can find rocks from the Lake District (shap granite) and rocks from southern Scotland here.


What's the difference between glacial landforms and fluvioglacial landforms?

Glacial landforms have been created or shaped by ice.
Fluvioglacial landforms have been created or shaped by glacial meltwater, created by abrasion.


What is the difference between glacial and fluvioglacial deposits?

GLACIAL - unstratified (difficult to identify the layers), angular material, unsorted.
FLUVIOGLACIAL - stratified (vertical layering due to seasonal/annual layers of sediment accumulation), smooth, sorted.


What is a lodgement till?

Subglacial material that was deposited by the actively moving glacier.
E.g. where a glacier is so overloaded with debris, it smears onto the valley floor.
An increase in ice thickness can also increase friction beneath the ice, causing lodgement.
A drumlin is a typical feature.


What is an ablation till?

Ice melts and deposits unsorted material.
Melting - solar radiation/geothermal heating.
Glacier retreats due to ablation at the snout - material is left behind.
Terminal, push and recessional morianes are typical features.


What is an erratic?

A large block of rock that has been moved from one area and deposited in another - has very different geology.
EXAMPLE - Norber Erratics, Yorkshire Dales.


What is a drumlin?

Smooth, oval-shaped hills.
1.5km long.
50-60m in height.
They have a steep end (STOSS) and a gently sloping end (LEE).
Found in groups known as swarms.
Deposition features.


How are drumlins formed?

Formed from unsorted till.
Subglacial landform.
Result of overload ice debris at the base.
Reduced the carrying capacity - deposition occurs at the base of the ice.
Moraine shunts the material.
The material deposited is also stream-lined by further ice advance - shaped and moulded rather than dumped.


What are the two types of drumlins?

ROCK drumlins and TILL Drumlins.
A Till Drumlin is a hill of compact, unstratified glacial drift or till.
A rock drumlin has a central core of rock.


What is an example of a swarm of drumlins?

Vale of Appleby - Yorkshire.
300m long.
500m high.


What is a lateral moraine?

Huge ridges of unsorted glacier sediment along the sides of the glacial valley - created by frost shatter and plucking.
Forms at the edges of the glacier.
It is mostly scree that has fallen off of the valley sides.
EXAMPLE: Surprise Glacier, Alaska.
2.5km long.
130m high.


What is a medial moraine?

Found in the middle of the trough, formed by two lateral moraines meeting together.
EXAMPLE: Surprise Glacier, Alaska.
5km long.


What is a recessional moraine?

Marks where the ice has paused in its retreat, and has deposited a huge ridge of material.
EXAMPLE: Surprise Glacier, Alaska.
50km high, several km in length.


What is a terminal moraine?

Marks the furthest point of glacial movement.
Unsorted, ridge, ablation material.
Elongated at right angles to the direction of ice advance.
Often crescent shaped.
Huge amounts of pile up at the snout.
Often steep-sided - 50-60m in height.
EXAMPLE: Athabasca glacier.


What is a push moraine?

If the climate cools for some time, it leads to a glacial advance.
A previously deposited moraine may be shunted up into a mound.
EXAMPLE: Surprise Glacier, Alaska.


What is a ground moraine?

Material which was dragged underneath the glacier and is simply left behind when the ice melts.
Forms uneven ground at a lodgement till.
Temperate glaciers - found between the two lateral moraines.
EXAMPLE: Grinnell Glacier, USA.


What are all the glacial deposits?

Lateral, medial, recessional, push, terminal and ground moraine.
Till - ablation and lodgement tills.


What is the definition of a moraine, and what are the 6 types?

Angular material transported and then deposited by the ice.
Lateral, medial, recessional, terminal, push and ground.