Geomorphological Depositional Landforms Flashcards
What are the 4 geomorphological depositional landforms?
1) Drumlins
2) Erratics
3) Moraines
4) Till plains
What is a drumlin?
Oval shaped hill formed beneath a glacier or ice sheet and aligned in the direction of ice flow
How is a drumlin formed? (2)
(Boulton Menzies Theory)
- When a glacier hits an obstacle that cannot be eroded, deposition from underneath the glacier builds up behind the obstacle
- Glacier then moves over the large mound and drags excess deposition over the other side
Steep side = stoss
Gentle slope = lee
What is an erratic?
A large rock that is of a different rock type to surrounding rock
How are erratics formed? (2)
- Boulder is broken off by weathering and erosion
- Then transported by a glacier and deposited when glacier loses energy
What are moraines?
Deposits of eroded material that are transported with the glacier
What is a lateral moraine?
A ridge of moraine along the edge of the valley floor
How is a lateral moraine formed? (3)
- Exposed rock on the valley side is weathered and fragments fall down on to the edge of the glacier
- This is then carried along the valley and deposited when the ice melts
- Parallel to ice flow
What is a medial moraine?
A ridge of moraine down the middle of the valley floor
How is a medial moraine formed? (3)
- When 2 valley glaciers converge, 2 lateral moraines combine to form a medial moraine
- Material is carried and deposited when melting occurs
- Parallel to ice flow
What is terminal moraine?
A ridge of moraine across the valley at the furthest point the glacier reached
How are terminal moraines formed? (3)
- Advancing ice carries moraine forward and deposits it at the point of maximum advance when it retreats
- The up valley side is generally steeper than the other side as the advancing ice rose over the debris
- Transverse to ice flow
What is a recessional moraine?
A series of ridges running across the valley behind the terminal moraine
How are recessional moraines formed? (3)
- Each recessional moraine represents a still stand during ice retreat
- They are good indicators of the cycle of advance and retreat that glaciers experience
- Transverse to ice flow
What is a push moraine?
A ridge of moraine with stones tilted upwards
How are push moraines formed? (3)
- Any morainic material at the glacier snout will be pushed forward during advance
- The faster the velocity of the advance, the steeper the angle of tilt and of clasts
- Transverse to ice flow
What are till plains?
Till is unsourced glacial material formed through erosion and weathering
How are till plains formed?
- When an ice sheet detaches from the main glacier melts
- This causes all of the till on top of and within the glacier to deposit on the valley floor
