Glaciers Flashcards
Striations
Long, parallel scratches left on rocks and bedrock by glacial movement
Can tell the direction of glacier movement from them
Glacial valleys
V shaped valley formed by erosion
Sedimentary rock, hills, but mostly very flat
Fertile farm land
Tectonics affect it
Arête
Sharp divide that separates to adjoining cirques
Crevasses
Great fissure/crack in glacier
Cirque
Semicircular basin found at head of a glacial valley formed by a valleyglacier
Drifts
All material of glacial origin (found anywhere)
Erosion, transport, deposit by glaciers
Drumlins
Long, smooth, egg shaped hill usually found in groups, shaped by an advancing glacier Layered Rock/glacial tills Surrounded by bogs/swamps 1-2km long 400-600m wide 15-30m high Composition varies
Eskers
Long, winding ridge formed when sand and gravel fill meltwater tunnels beneath a glacier Ridges of sand and gravel Hundreds of kms Gravel is rich (used to build stuff) Show direction of motion (The drugs drawing)
Erratics
Large Boulder that has been transported into an area by a glacier
Horns
Pyramid shaped peak formed when three or more cirques meet
Kettle lakes
A kettle filled with water
Kettles
Bowl-like hollow in deposits of glacial outwash; formed by the melting of a large block of ice left behind by a glacier
Some partially buried (sediment flowing down)
Some completely buried (sediment collapsing)
Kames
Small Come shaped Sand and gravel Water pulling it off the surface (Unwanted dirt drawing)
Moraine
Deposit of till left behind when a glacier retreats Has forests Wetlands Streams Vegetation Aquifer Woodelts (Burn drawing)
Outwash plains
Broad, stratified gently sloping deposit of sediment formed beyond the terminal moraine by streams from a melting glacier
Flat stuff in front of a glacier
Plucking
Phenomenon responsible for erosion and transportation of individual pieces of bedrock
Valley glaciers
Till
Unsorted and unstratified Rock material deposited directly by glacial ice
Glacier
Large mass of compacted snow and ice that moves under the force of gravity
How do glaciers form?
More snow falls than melts
Firn
Granular snow on the upper part of a glacier that has not yet been compressed into ice
Valley glacier
Within valley walls Go downhill because gravity In mountains May be <2km or >100km Hundreds of m thick Create glacial valleys and cirques
Continental glacier
Covers large part of continent Form because more snow falls than melts Thousands of m thick 3km thick 1.7km^2 in area Create round peaks
Ice cap
A glacier < 50 000 km^2 in area
How do glaciers move
Plastic flow
What part of a glacier moves the faster
Surface and centre
Bottom is slush (ice melts and refreezes)
Basal slip
Meltwater between glacier bottom and surface
Makes less friction so glacier moves faster
Plastic flow
Ice grains deform, can be almost flat and slide past each other
Creates forward movement
Ice front
Ice melting at end of glacier
Connection between icebergs and glaciers
Glaciers become icebergs
When did the Great Lakes form
10 000 years ago
Why are the Great Lake basins so deep
They don’t drain into the sea (so they erode the bottom of the basins)
How deep are the Great Lake basins
Well below sea level (164m, 52m, 105m, 215m)
Michigan and Huron formation
Selective erosion of weak rock layers
Also same as Lake Ontario - but they were connected and going through different isostatic rebound
Ontario and Erie formation
St Lawrence River stuff
Laurentide ice sheet
Ordovician shales (soft)
Superior formation
Mid-continent rift
Warsaw
Fissure caves
Fissure caves
Large caves underground with collapsed roofs
Large limestone blocks tilting down into the collapsed caverns
How were drumlins made?
Who knowsssss -close to ice margins? -same time under ice sheet swathes? -2-stage: fluvially-deposited A good theory: explains full range of observations, variations in shape/scale/composition
Glacial lake Algonquin and Iroquois
Giant lakes where the Great Lakes are now
They drained and that’s how we have the lakes we have today and y’know all the other cool stuff
Karst topography
A landscape characterized by numerous caves, sinkholes, fissures, underground streams
Roches moutonnés
Small, bare outcrop of rock shaped by glacial erosion, with one side smooth and gently sloping and the other steep, rough, irregular