3.1.4.4 Glacial Deposition Landforms Flashcards
2 ways debris transported by a glacier will eventually be deposited
- when it’s released by ice melting at snout
- when ice becomes overloaded with material
What’s the most common till
Ablation till at snout
What’s the name for subglacial debris till
Lodgement till
What are the 4 landforms formed by glacial deposition
Drumlins
Erratics
Moraines
Till plains
What’s a drumlin
Smooth egg-shaped hill up to 1.5km length + 50-60m in height
What are the 2 ends of drumlins like
What do they show
Steeper ‘upstream’ end + gently sloping ‘downstream’ end
Show direction of ice advance
Where are drumlins formed
Beneath glaciers
What’s the most popular theory of how a drumlin forms
The glacier being overloaded by moraine compared to the energy it has, so struggled to cope with transporting the amount in the lower parts of the course and so deposits it
What end of the drumlins means what
Blunt end - facing oncoming in
Tapered end - is the lee
2 other theories of how drumlins form
Obstacles (resistant rock) in glaciers path encourage deposited material to be moulded into the drumlin shape
Glacial meltwater is responsible for eroding large hollows beneath ice and then infilling causing drumlins
What are erratics
Rocks picked up + carried by ice, often for many kilometres and then deposited in areas of completely different lithology (rock type)
What can you track by erratics
Track ice movements, by determining where rocks originated from
What are moraines
Lines/series of mounds of material mainly running across glacial valleys
What moraine is found at the snout
Terminal/end moraine
Describe terminal moraine
Steep-sided
Can reach up to 50-60m high
Often moulded to the form of the snout
When do terminal moraines form
When ice melts during snout standstill, when its reached its furthest point down a valley + material has been deposited
When can recessional moraines be formed along the length of the valley
As the glacier retreats
What are till plains
Wide areas of flat relief created by a till sheet (thick glacial till, sand + gravel)
Where are rill plains often found
Behind a terminal moraine/towards former ice sheet margins
Why are till plains usually poorly drained with bigs, lakes and slow moving meandering streams
As depth can vary and a lot of material tends to be compacted
When are till plains formed
When ice melts leaving a layer of till behind
What’s drift
All glacial deposits (subdivided into till + glacifluvial material)
What’s till
Unsorted mixture of rocks,clay and sand mainly transported as supraglacial + englacial debris and then deposited
(all material deposited by glacier itself)
What’s glacifluvial material
All material deposited by meltwater streams
