Glaciers
arete
a knife edged ridge formed by two cirques that have eroded towards one another
horn
a pointed mountain peak formed by 3+ cirques that surround a peak
glacial abrasion
a sandpaper effect on substrate striations run parallel to direction of ice movements
zone of ablation
area of net ice loss
zone of accumulation
area of net snow addition
how do glaciers move?
basal sliding: meltwater forms at base of glacier, water decreases friction and ice slides plastic deformation: occurs below about 60m depth, grains of ice slowly change shape, new grains form while old grains disappear, crevasses form at surface, upper zone too brittle to flow
erratics
boulders dropped by glacial ice
cirques
bowl shaped basins high on a mountain
types of mountain glaciers
cirque glaciers:fill mountain top bowls valley glaciers: flow like rivers down valleys mountain ice caps: cover peaks and ridges piedmont glaciers: spread out at the end of a valley
glacier-forming conditions
cold local climate (summer wont melt snow) abundant snow (more fall than melt) snow not removed by avalanche or wind
depositional landforms
end moraines: form at toe of glacier terminal moraines: farthest edge of flow grounds moraine: till left behind by rapid ice retreat kettle lakes: formed from stranded blocks of ice eskers: long channels of gravel and sand
glacial drift
glacial till, erratics, loess
major ice sheets on earth
greenland and antarctica
mountain glaciers
high to low elevation in mountain setting
glacial consequences
ice loading and glacial rebound sea level rise and fall pluvial features- large lakes formed during ice age
causes of glaciation
plate tectonics, atmospheric chemistry, changes in orbital geometry
glacial till
sediment dropped by glacial ice all grain sizes, unsorted, unstratified
how a glacier forms
snow is transformed into ice, buried by later falls, compresses, melts and recrystallizes, interlocks can form over tens or thousands of years
toe
the leading edge of a glacier
why do glaciers flow?
the pull of gravity is strong enough to make ice flow;glaciers move in the direction of its surface slope
glaciers
thick masses of recrystallized ice that last all year long, flow via gravity, and are both mountain and continental presently cover 10% of earth
moraines
unsorted debris deposited by a glacier lateral: forms along flank of a valley glacier medial: mid ice moraines from merging of lateral moraines
continental glaciers
vast ice sheets covering large land areas ice flows outwards from thickest part of sheet
equilibrium line
where the zone of accumulation and zone of ablation meet
loess
wind-transported silt unstratified deposits