GL 4 Flashcards
What is fluvial glacial transport?
Transport of debris by meltwater
What does entrained rock debris mean?
Rock debris inside the glacier
What are the four locations of debris
Surface (supraglacial) , Within (englacial), Base (subglacial), Front (proglacial)
What is an erratic?
Different rock types to the bedrock
What is an example of an erratic?
Canadian Rockies, transported over 300km and weigh over 16 000 tones
How can debris mover from one area to another. What does some of this this depend on?
Supra -> englacial, snow covers supra debris, making it englacial, this causes layers of debris and ice
Englacial -> Supra, glacier melts top layer
Depending on the topography of the ground,
extensional flow, causes debris to flow into crevasses, becoming englacial
compressional flow, sub or englacial material is moved towards the surface (supra)
What landforms are deposited by glacial ice, where are these found?
Drumlins, Terminal moraines, recessional moraines, Lateral moraines, medial moraines, push moraines.
These are found in the till planes
What landforms are deposited by meltwater (fluvioglacial), Where are these found? Why?
Eskers, Kames, Kame terraces, Kettle Holes, Kettle Lakes, Varves. These are found in sandurs, or outwash plains, because the glacier has never reached
What is glacial deposition called?
Glacial till
What is Lodgement till?
What is lodgement till composed of?
How is till orientated?
Till that is plastered into the surface.
Rounded, compacted boulders, matrix of sand, mud and clay.
Orientated facing in one direction, the long axis shows direction of moment (aligned with the ice flow)
What is an example of lodgement till?
Aberogwen
What is Ablation till?
What is it composed of?
Where is this usually found?
Material is deposited due to ablation.
Composed of compacted, unsorted, unstratified material, meltwater removes finer (clay particles)
Found at the snout, ablation occurs, so glacier drops all the sediment, like a conveyer belt
What is deformation till?
Wat is it composed of?
How is it formed/
sediment if folded, into well compacted shapes, composed of man materials.
Formed when a glacier re advances over a previously deposited till
What is a moraine?
Accumulation of debris, left behind by a glacier after it retreats.
What is a till plain?
Size?
Example
Flat area, formed by a glacial moraine, up to 50m thick.
East Anglia
What is a drumlin?
Where/how is it formed?
How can the direction of glacial ice be seen?
Why may it be hard to distinguish drumlins, what is multiple drumlins called?
Elongated hill, streamlined tail.
Formed sub glacially
Fluvial theory - Formed from subglacial meltwater flooding, deposits are then streamlined by glacial ice
Deformational theory - (accepted), glacier moves over an obstacle, till is plastered around it, becoming streamlined
Movement is seen by the direction of the long axis
Vegetation has grown over drumlins, making them harder to see
What is an Example of a Drumlin?
Found throughout Conwy valley
What is a lateral moraine?
What margin is it?
How is it formed?
Moraine that forms on the edge of a glacier
Ice-Marginal Landform
Rocks from freeze thaw weathering on rocks above the glacier fall on the sides of the glacier, or debris is wind blown.
What is a medial moraine?
What margin is it?
How is it formed?
Can it be seen after glacier retreat?
Moraine that form in the middle of a glacier
Ice marginal landform
Two valley glaciers meet (confluence). Two lateral moraines merge.
Cannot be seen after glacier melts?
What is a terminal moraine?
How is it formed?
Moraine that marks the furthest advance of a glacier. (Snout)
Glacier has a negative mass balance, so is retreating, causing the deposition of debris and boulders. After the glacier has fully retreated a terminal, crescent shaped moraine is left
What can terminal moraines act as for meltwater?
Act as a dam for proglacial lakes
What is a recessional Moraine?
How is it formed?
Where are they found?
Representation of where a glacier has paused for a time during retreat.
Formed in the same way as terminal
Found behind the terminal moraine, in bands
What is a push moraine?
What is the orientation of clasts, due to the formation
Glacier advances over existing moraine.
Clasts orientate themselves vertically
Not permanent
Why is glacial debris more angular when transported englacial then subglacial?
Englacial - few changes, position is fixed
Subglacial - Abrasion occurs, forming rock flour.