Glaciers: Geomorphological Landforms Flashcards
What are the Erosional landforms?
- corries
- arêtes
- glacial trough
- hanging valley
- roches mountonees
What are the depositional landforms?
- till plains
- erratics
- drumlins
- moraines
What are corries?
form when snow continues to build up in a depression/nivation hollow, eventually compacting to form a glacier that is trapped in the hollow, the only movement being rotational slip. The back wall is eroded through plucking and frost shattering and hollow deepened through rotational abrasion. Leaves an armchair-shaped rock hollow, with a steep back wall and an over-deepened basin with a rock lip. Often contains a small lake (a tarn). They last a long time.
What’s an example of a Corrie?
One example is Red Tarn - the Lake District
What are arêtes?
a knife-edged ridge formed between two corries (when the two back walls meet) if three meet, it is called a pyramidal peak.
Whats an example of an arête?
An example of this is the Striding Edge Arête in the Lake District
What’s a glacial trough?
glaciers flow down pre-existing river valleys as they move from upland areas. They straighten, widen and deepen these valleys, changing the original shape from a V to a U or trough shaped valley - typical of glacial erosion. The action of ice, huge amounts of meltwater and sub-glacial debris has a far greater erosive power than the pre-glacial river. It erodes away a rivers interlocking spurs and leaves smooth, but steep truncated spurs on the valley sides. The river than originally flowed, will continue to flow, giving it the name misfit stream due to its small size in comparison to the surroundings.
What’s an example of a glacial trough?
An example is the Glen Geusachan, The Cairngorms.
What is a hanging valley?
a main feature of a glacial trough is a hanging valleys on the side of the main valley. It is a smaller U-shaped valley caused by a tributary glacier. The smaller glacier does not have enough energy to erode to the valley floor, leaving a hanging valley. Waterfalls often form here. Last a long time, yet the waterfalls can erode the hanging valley.
What’s an example of a hanging valley?
An example of this is the Fiordland National Park, New Zealand.
What is a Roches moutonees?
a mound of rock shaped by a glacier flowing over it and eroding it. right (stoss side) and left (lee side). The glacier hits an obstacle that is too large and hard to pluck -so must go over it. This increases fiction and pressure, therefore increasing melting as the lower ice can reach the PMP. The meltwater allows the glacier to slide over the rock, and smaller rocks will abrade the stoss side (right). When it reaches the top, friction and pressure drop and meltwater re-freezes. Frozen rocks are plucked from the lee side - leaving it jagged.
What’s an example of Roches Moutonnees?
An example is Myot Hill, Falkirk, Scotland.
What are till plains?
an extensive flat plain of glacial till - till is material deposited by a glacier, either when the ice melts/retreats (ablation) or is there is too much material for the glacier to transport. It is an unsorted mix of angular rock, clay and sand. Till plains form when an ice sheet detaches from the main glacier and melts, causing all of the till on the top and within the glacier to deposit on the valley floor. They can last a medium to long amount of time, but can be disrupted.
What’s an example of a till plain?
One example of this is Saskatchewan Glacier, Alberta
What’s Erratics?
a large boulder of a different type of rock, that had been broken off by weathering and erosions, then transported by a glacier and deposited when it has been moved to a different location and lost energy.
What’s an example of an erratic?
What’s a drumlin?
when a glacier hits an obstacle that cannot be eroded, deposition from underneath the glacier builds up behind the obstacle. The glacier moves over the mound and drags excess
deposition along the sides - this causes a teardrop shape with a long tampered edge. Can be ap. 1500m long and 100m high. Usually in groups called ‘Swarms’.
What’s an example of a drumlin?
One example is Eureka Drumlin Field, Montana.
What is a moraine?
type of landform which develops when the debris carried by a glacier is deposited.
There are different types.
What’s a lateral moraine?
material deposited on the sides of a glacier, leaving a ridge when the ice melts
What’s a medial moraine?
distinct ridge of debris occurring on the surface of a glacier where two streams of ice merge (two lateral moraines meeting in the middle)
What’s a terminal moraine?
a prominent ridge pf glacial debris formed when a glacier reached its maximum limit during a sustained advance.
What is a recessional moraine?
forms at the end of a glacier, when a retreating glacier stays stationary for a sufficient time. Usually shows smaller, seasonal retreats
What’s a push moraine?
a complex landform ranging from a few metres to tens of metres in height compromising assorted debris that has been pushed up by a glacier during an advance.
Moraines can last a medium amount of time, as they can be displaced.
What’s an example of a moraine?
An example of a moraine is Wrangell-St Elias, Alaska.
