Cold enviroments landforms Flashcards
What are the 3 main processes of erosion/weathering by and around glaciers
Plucking, abrasion and frost shattering
What are the grooves left behind after abrasion called?
Striations
What is the difference between erosion and weathering?
Weathering occurs in situ whereas erosion occurs by movement
What process occurs on north/east facing slopes under snow?
Nivation
Describe the process of nivation
Snow builds up on north/east facing slopes away from the sun. Beneath the snow, frost shattering occurs causing the rock to disintegrate. A nivation hollow can be formed.
Describe the features of a corries
An enlarged armchair like hollow with a steep back wall and an over deepened basin. A tarn often forms in the basin due to the raised lip and deep base.
Describe how a corrie is formed
Corries often form as a result of deepening pre exsisting nivation hollows on north/east facing slopes. As the hollows get deeper, névé is formed under the snow. This build up more and more and eventually turns to ice. The ice moves and rotates plucking material from the back wall and abrading the floor of the hollow. The rock lip forms as the thinner ice erodes slower.
What other landforms are a result of corries?
Arêtes and pyramidal peaks
Descibe the features of a glacial trough
A U shaped valley with a wide floor and steep sides, often with misfit streams, ribbon lakes, truncated spurs and hanging valleys
How are ribbon lakes formed?
Compressional and extenstional flow in the glacier mean that the rock under the glacier is eroded at different rates forming rock basins. This occurs even more where the geology changes resulting the softer rock being eroded faster. Post glaciation this is often filled with water forming the ribbon lake.
What are the 2 landforms found on the valley floor as a result of glacial erosion on hard rocks?
Roche mountonées and crag and tails
Describe a roche mountonée
They have a sloping stoss side in the direction of ice movement and a steep lee side where the hard outcrop of rock ends. On the stoss side there are striations showing abrasion and on the lee side the rock is broken and rough showing plucking
Describe a crag and tail
A crag and tail has a steep crag/stoss side made of hard rock and a sloping tail/lee side made of softer rock which is protected from the glacial erosion by the hard rock.
What are the 3 places glaciers can transport material?
On top of the glacier - supraglacial
In the glacier - englacial
Under the glacier - subglacial
What are the 2 types of deposited material by the glacier?
Till and fluvioglacial material
What are the main differences between till and fluvioglacial material?
Till is unsorted, angular material that has been dropped by the glacier
Fluvioglacial material is sorted and eroded material which has entered meltwater streams beneath the glacier
What are erratics?
Fragments of rock carried by the glacier that have been deposited, they often have a different geology to the area as they may have moved hundered of miles
What are the 5 types of morraine and where are they found
Lateral - edge of a glacier
Medial - between a confluence of glaciers
Terminal/end - the furthest point the glacier reached
Recessional - behind and parallel to end morraines
Push - the new furthest point the glacier reached
What is the gap between the valley side and the glacier called?
The bergshrund crevasse
What is another name for the outwash plain?
The sandur
What is and esker and how is it formed?
An esker is a ridge of sediment which runs down the outwash plain. It is formed when a meltwater stream in the glacier deposits sediment in the channel. As the streams have high carrying capacities large amounts of sediment can be dropped. As the glacier retreats and the ice melts the river bed fills up with water building up the ridges of sediment
What are the 3 types of kame?
Crevasse kames, terrace kames and kame deltas
How are kame terraces formed?
When meltwater streams run down the side of glaciers the carry sediment from the glacier which are eroded and sorted. When the glacier melts the sediment left being lines the edge of the valley like terraces. These are similar to lateral moraines except kames are sorted and eroded.
How are crevasse kames formed?
Sediment runs into crevasses by meltwater stream on top of the glaciers. When the glacier melts the sediment is deposited on the valley floor.
How are delta kames formed?
When a meltwater stream enters a glacial lake it deposited it’s sediment. This forms eyots typically associated with braiding and deltas. When the ice melts only the kames are left.
Why are braided streams very common around glaciers?
Because they have a high amount of variable discharge and a large carrying capacity to carry sediment.
How are kettle holes formed?
When calving occurs and large pieces of ice fall off the end of the snout of the glacier they become embedded in the outwash plain. They eventually become covered in material and buried. When the temperature warms up they melt leaving a hole where they were which often fill with water.
How can varves be used to understand changes in temperature?
The warmer a year is, the more meltwater runs out of a glacier, this means there will be more sediment deposited in pro glacial lakes. By looking at the deposits for each year we can tell how warm or cold the year was
How does patterned ground form?
Small pockets of water in the ground are insulated by large rocks above it. This means they stay frozen as ice lens’ while the land around it thaws. This causes frost heave which pushes the large rocks about it up. The gaps left are filled with sediment. The rocks are eventually pushed out the ground to the surface.
How to solifluction lobes form?
When there is a large active layer above permafrost the melted soil will saturate the ground. This large amount of water reduced friction in the soil allowing it to creep forward creating the ridges/lobes
How are open system pingos formed?
In areas of discontinuous permafrost water collects in talik between areas of permafrost. When temperatures drop the advancing permafrost pushes water in the talik together where it freezes forming a large ice core. This pushes the ground above it up forming the pingo.
How are closed system pingos formed?
These are formed from periglacial lakes with continuous permafrost. The lake insulates the ground rom permafrost however as it is filled by sediment the ground and ground water collected freezes. This forms the ice core and pushes up the ground forming the pingo.
How are ice wedge polygons formed?
The active layer freezes in winter which causes it to contract, this pulls the ground apart in some areas which allows wedges in the ground to form. In spring frost shattering can occur which forces the wedges wider. This occurs over 100s of years enough to form wedges 8-10m deep. They often form polygon shapes.
What are loess’ and how do they form?
Loess’ are a collection of loose sediment from periglacial areas that have been collected after being eroded by wind action and abrasion and blown across long distances before an obstacle blocks its path.
Define a periglacial area
Periglacial areas are areas that while not glaciated, experience very cold climates and intense frost action and the development of permafrost.
