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8.3 Glaciers
Types of glaciers
AlpineSmall glaciers that form valleys
Ice sheetsEnormous glaciers that can cover entire continents
Glacier FormationDescribe the steps
Thick, dense compacted snowFirn:
Firn compacts into glacial iceGlacial ice:
Advancing: A glacier growing faster than it is melting
Retreating: A glacier melting (receding) at the leading edge faster than its growing. It’s NOT traveling backwards.
Glacier Movements
Plastic Flow
Deep within, there is a huge amount of pressure due to weight of ice pressing down.
50 meters thick of ice creates enough pressure to cause ice to flow through the center of a glacier very slowly.
Describe:
Glacier Movements
Basal Slip
Water beneath glacier acts as a lubricant, so entire glacier can slide. This movement can cause a large crevasse (crack), to form.
Describe:
Rate of movement:
Typically a few meters/ day, but can have faster surges.
Glacial structures from erosionStriation
Long scratch marks found in rocks due abrasion caused by rocks & gravel dragged by glacial movement.
Describe:
U-Shaped ValleysV-shaped valleys that are widened by glaciers.Describe:
Glacial structures from erosionHorn peaks
When several cirques converge, the part that is not cut out looks like a horn sticking out of the ground.
Describe:
Cirques
Valleys that look like giant armchairs because they have 3 steep sides & one open side.
Describe:
Glacial structures from erosionFjords
Very steep inlets to the ocean.Describe:
Roche moutonnees
Landforms w/ 1 rough side & 1 side that has been abraded smooth.
Describe:
The coarsely graded sediment deposited by glaciersDescribe:
Till
Unsorted glacial sedimentDescribe:
Glacial Drift
Big rocks deposited by a glacier into an area w/ a different type of rock.
Describe:
MorrainesPiles of boulders, rocks, pebbles, & clay left behind by a glacier.
Describe:
Structures FormedGlacial Erratics
form at the edge of glaciers.Describe:
DrumlinsSmooth, egg-shaped hills left behind by continental ice sheets.
Describe:
Structures FormedTerminal Moraines
Deposits left by melted water coming off a glacier.Define:
kettlesWhen large blocks of ice get trapped under stratified drift, the ice melts and leaves large holes.
Describe:
Stratified Drift
Structures Formed:
Describe: Winding ridges of sand & gravel left behind by receding glaciers.
Eskers
Earth’s OrbitChange in Earth’s orbit around the sun cause slight temperature variations.
Effects:
Effects: The tilt of Earth’s axis changes over time & can affect the amount of sunlight reaching different parts of earth.
Precession