Topic 9 Glaciers Flashcards
What is a glacier?
a slow moving mass or river of ice formed by the accumulation and compaction of snow
How do glaciers form?
When annual snow fall is greater than annual snow melt
What are the two types of glaciers?
Alpine glaciers: glaciers found in mountainous areas
Ice sheets: domed sheets of ice that can cover significant parts of a continent
What are the four main types of Alpine glaciers?
Cirque glacier: found at the head of a valley
Valley glacier: glacier that occupies a mountain valley
Pledmont glacier: lobes of ice that form as a glacier flows onto a flat plain
Ice cap: a large dome of ice that sits over a high mountain
What are tidewater glaciers?
glaciers that terminate in a body of water
Why do glaciers move?
Ice deformation and motion at the base of the glacier
what impacts glacial ice velocity?
Distance from bed and valley sides (friction)
Surface slope
Free water at the bed (lubrication)
describe the velocity characteristics of glaciers
high velocity on the surface layers with low deformation, low velocity near the base with much deformation
Describe the mass balance of a glacier
zone of accumulation is the top half of glaciers, net ice gain above the equilibrium.
equilibrium is where snow fall and melting rates are the same
Zone of ablation is where the net ice loss occurs below the equilibrium
describe glacial advance and retreat
Glacial advance is when the glacier has a positive mass balance
glacial retreat is when the glacier has a negative mass balance
what is the global state of glaciers?
more than 90% of glaciers are retreating in response to global warming
What are the three primary erosion processes in glaciers
plucking: the removal of rock fragements and joint blocks from the bed
Abrasion: the wear of a bedrock surface by rock fragments
Chemical denudation: net dissolved mineral mass loss in solution from underneath the glacier
