Flashcards in Glacier Land Forms Deck (19)
Describe the formation of a glacier?
As more snow falls the pressure makes the earlier snow melt
Repeated melting and refreezing forms grandes called firm or néve
Further compression firms layer crystals of glacial ice (it can take 30-40 years for snow to form dense glacial ice)
It now moves downslope under its own weight
What is an ice sheet?
A large body of ice over 50,000 km squared in extent
What is an ice cap?
A smaller body of ice (less than 50,000 km squared)
Usually found in mountainous regions
What is a glacier?
A finger (river) of ice usually extending down hill from an ice cap or occupying a valley
Describe the formation of a Corrie?
Snow collects in the hollow and overtime is compressed to form ice
Freeze thaw weathering steepens the back wall and provided material for abrasion
Plucking and abrasion deepen the Hollow as the glacier moves by rotational slip (due to gravity)
Temperatures warm and the glacier melts, some rocks are deposited creating a lip which dams the Corrie and keeps melted water in creating a tarn lake
What is an arête ?
Sharp narrow ridge separating two corries
Formed when two or more corries are back to back / side to side
Describe the formation of at arête?
Formed when two glaciers flow in parallel valleys
The back walls erode towards each other (through freeze thaw weathering and plucking) so the land between them gets narrower
Until a knife edge ridge forms know as an arête
What is an example of an arête?
Striding edge in the Lake District
What is a pyramidal peak?
Angular mountain peak with three or more arêtes found in a glacial valley
Describe the formation of a pyramidal peak?
When three corries are back to back freeze thaw weathering and plucking both steepen and narrow the back wall making the sides steeper and narrower creating a pyramidal peak
Describe the formation of a hanging valley?
They are valleys formed by tributary glaciers that flow into the main glacier r
The glacial trough is eroded (abrasion) much quicker by the larger glacier due to them having a greater erosive power
Thé glacier also bulldozes interlocking spurs creating truncated spurs so when the glacier melts due to increased temperatures the trbituatory valleys are left at a higher level
They are often marker by waterfalls
Describe the formation of a glacial trough?
As the glacier moves through the former river valley a V shaped valley becomes a U shaped valley
Freeze thaw weathering and plucking provide material for abrasion which deepens and widens the valley
Describe the formation of truncated spurs?
As a result of erosional processes and the weight of the glacier the interlocking spurs of the former river valley are bulldozed out of the way to create the steep sides of a glacial trough
The rock left is known as a truncated spur
What are the characteristics of a glacial trough?
Steep valley sided
Wide and flat valley floor
What is a ribbon lake?
A long thin lake that form after a glacier retreats
Describe the formation of a ribbon lake 1?
The glacier finds it difficult to erode hard rock
The glacier easily eroded the soft rock forming a rock basin
When the ice melts the water remains in the hollow created by the soft rock
The ribbon lake is dammed by a rock bar and moraine may be deposited by the glacier also damming the lake
Describe the formation of a ribbon lake 2?
Tributary glacier join the main glacier giving the main glacier additional erosive power at that point
The glacial trough is eroded more deeply here creating the ribbon lake when the glacier melts
What is an erratic?
A glacial erratic is a piece of rock that is different from the size and type of rock in that area