Dynamic Surface L12 Flashcards
What is the snowline?
The lower topographic limit of permanent ice and snow
What is the main effect on snowline?
Latitude
What is snow’s crystal structure?
Hexagonal
What is ice’s crystal structure?
Cubic
What is glacier ice’s crystal system?
Hexagonal
What is frazil ice?
Ice that forms in supercooled turbulent water
At what temperature does frazil turn into sea ice?
-1.8C
What is pack ice?
Consolidated sea ice
How do icebergs affect sedimentation?
Icebergs contain sediment from the continent and float considerable distances away from their source depositing sediment when they melt.
Describe the crystal structure of ice.
H2O molecules are arranged in tetrahedral patterns that form hexagonal rings of oxygen atoms. A single crystal of ice consists of stacked layers of these rings.
What is the basal plane?
The plane of hexagonal rings in ice
What is the c-axis of ice?
The direction of stacking of the layers of hexagonal rings in ice
What is polycrystalline ice?
Ice that contains many grains with different orientations of their c-axes.
What determines the fabric of ice?
The way in which the c-axes are orientated relative to each other
What is basal glide?
The deformation of a single crystal when shear stress is applied along its basal plane
What does the pressure on ice needed for it to flow depend on?
Gradient
How does cold dry ice flow?
By internal deformation
How does meltwater and wet sediment help ice to flow?
By acting as lubricants between the ice and the bedrock
What are the 4 types of glacial environments?
Ice sheets
Valley glaciers
Tidewater glaciers
Piedmont glaciers
What is a tidewater glacier?
Where a glacier meets the sea
What is a piedmont glacier?
A glacier that is found at the foot of a mountain and forms from the amalgamation of several valley glaciers
What is the ablation zone?
The zone along a glacier in which ice loss is greater than ice gain
What is the accumulation zone?
The zone along a glacier in which ice gain is greater than ice loss
When does a glacier retreat?
When ablation > accumulation
When does a glacier advance?
When accumulation > ablation
How does a temperate glacier flow?
Ice moves over the bedrock
How does a polythermal glacier move?
Ice moves by internal shearing but over the bedrock during glacial surges
What is a moraine?
Piles of disturbed unsorted material at the sides or front of the glacier
Is moraine well or poorly sorted?
Poorly sorted
What is a drumlin?
Oval shaped hill composed of ground moraine that form below the glacier in the direction of ice flow
What is terminal moraine?
Sediment that has been deposited at the nose of the glacier at its maximum extent
What is a kettle hole?
Ice dropped off at the nose of the glacier into the moraine eventually melts leaving behind a pond of melt water
What is an esker?
A sinuous deposit of sorted sediment that forms when subglacial streams drop their sediment.
What is a lateral margin stream?
Streams of water that flow between the valley side and the glacier that often deposit sediment forming kame terraces.
What is a kame terrace?
Sediment deposited by lateral margin streams at the sides of the glacier.
What is a sandur?
An outwash plain formed by glacial meltwaters
What are some features of sandurs in the geological record?
Sandstone dykes
Frozen sand clasts
What are glacial dropstones?
Large pieces of sediment that have been carried out to sea by icebergs and dropped to the sea floor during melting
What are glacial varves?
A very thin annual layer of sediment deposited during cycles of melting
What is isostatic rebound?
The rising of the lithosphere which has previously been depressed by the weight of glacial ice
