Landforms of glacial deposition - Ice marginal moraines Flashcards
What are ice-marginal moraines?
Ice marginal moraines are landforms deposited at the margins of glaciers.
Why do ice-marginal moraines form?
Ice-marginal moraines form as the result of ablation along the edges of a glacier.
How are ice-marginal moraines classified?
The basis for classification is the location of the material in relation to the glacier snout.
What are the five types of ice-marginal moraines?
- Terminal or end moraine
- Recessional moraine
- Push moraine
- Hummocky or disintegration moraine
- Rogen/flute moraine
What are the characteristics of a terminal moraine?
- Arcuate shaped (curved) ridge of moraine extending across the valley marking the furthest point reached by the glacier
- They are transverse to ice flow
- They typically vary between 30 meters to 60 meters high
Describe the formation of a terminal moraine?
Advancing ice transports debris forward and deposits it at the point of maximum advance by ablation. The up-valley (ice-contact) side is generally steeper than the other side as the advancing ice supports the debris.
Describe the characteristics of a recessional moraine?
A series of ridges transverse to ice flow, located behind the terminal moraine.
Describe the formation of a recessional moraine?
Each recessional moraine, and there may be many, represents ablation associated with a stillstand (when the margin of the ice sheet is stationary) during ice recession. They are smaller than terminal moraines and indicative of the cycles of advance and recession that many glaciers experience.
Describe the characteristics of a push moraine?
- A ridge of moraine with stones tilted upwards
- Transverse to ice flow
Describe the formation of a push moraine?
Any morainic material at the glacier snout will be pushed forward during ice advance. The faster the velocity of advance, the steeper the angle of tilt of stones.
Describe the characteristics of a hummocky moraine?
- Chaotic jumble of till mounds
- Limited orientation
Describe the formation of a hummocky moraine?
Associated with polythermal glaciers with thick debris-rich basal ice layers in their lower areas, with meltwater channels at their margin and underneath, producing a jumble of mounds.
Describe the characteristics of a rogen/flute moraine?
- Irregular landforms 10-20 meters high, 50-1,000 meters wide and 1-2 km long
- Arcuate in appearance and concave in the up-ice direction, they are separated by lakes and often mark the transition to drumlins
- Transverse to ice flow
Describe the formation of a rogen/flute moraine?
It is thought that rogen moraines were deposited in water at the ice-margin during ice recession.
