Glaciers Flashcards
What are glaciers
A glacier is a large mass of ice that moves slowly over land. They are often called rivers of ice.
Inputs - snow and rain
Outputs - meltwater and moraine
How do glaciers grow
Glaciers grow when their inputs exceed their outputs.
When they grow (accumulate), the snout of the glacier advances.
When they shrink (ablate), the snout retreats.
What is meltwater
Water under the glacier -
Lubricates the glacier -helps it to move by a process called basal sliding
Meltwater - between ice and ground
If temperatures are cold enough, meltwater can freeze for that period of time, the glacier stops moving
What is moraine
a mass of rocks and sediment carried down and deposited by a glacier
State the glacial processes
freeze-thaw weathering
- erosion – abrasion and plucking
- movement and transportation – rotational slip and bulldozing
- deposition
Explain freeze-thaw weathering as a glacial process
As water enters the cracks in the mountain face it freezes in the cracks and expands by up to 9% which widens the crack , creating a weakness.
This process repeats until parts of the mountain face break off leaving a jagged landscape.
Often takes place at the top of the mountain where conditions are coldest which shapes the landscapes you see in glacial environments
As Glaciers advance, they ____________
As Glaciers advance they erode the landscape in two ways: abrasion and plucking
Explain the process of abrasion as a glacial (erosional) process
Bits of rock which are stuck in the ice grind against the rock below the glacier, wearing it away
Explain the process of plucking as a glacial (erosional) process
Meltwater at the base, back or sides of a glacier freezes onto rock (on the glacier bed). As the glacier moves forward it pulls out pieces of rock
How glaciers transport sediment
Rotational slip
Bulldozing
Describe the process of bulldozing as a movement and transportation process
As a glacier moves downhill it pushes loose sediment ahead of it by sheer force. This pushes the material downhill
Descibe the process of rotational slip as a movement and transportation process
When the glacier moves out of a hollow in a circular motion
Occurs in north facing hollows in uphill areas
Explain the process of deposition
Most of the deposition takes place at the snout of the glacier
If a glacier is overloaded with material, or when the ice melts, the material is deposited on the valley floor, forming landforms such as moraines and drumlins
What is till
Unsorted glacial sediment that forms moraine
What is outwash
This is when fine material such as sand and gravel (deposits of moraine) get washed away from the front of the glacier by small meltwater streams
The streams sort the material by size and deposit it in layers called outwash, in the front of the glacier
It is sorted as the water loses energy