glaciers / types
thick mass of ice originating on land from the accumulation, compaction, and recrystallization of snow
-hydrologic cycle and rock cycle
valley: confined to flow down a mountain valey
ice sheet
very large thick mass of glacier ice flowing outward in all directions from one of more accumlation center, large
antarctic ice sheet
contains 80% of earths ice and 66 of fresh water. covers almost 150 of the area of the US. if melted the global sea level would RISE
formation of a glacier
glaciers form in areas where more snow is added than melts or evaporates
formation of glacial ice
-snowflakes becomes smaller thicker and more spherical
-air is forced out of pore spaces
-snowflakes recrystallized into denser masses of small grains
-under pressure firn fuses into solid mass
glacial flow
accumulation of snow and ice at high elevation causes glacial ice to flow downslope because of the pull of gravity
types of glacial flow
basal slip- mechanism of glacial movement in which the ice mass slides over the surface below
plastic flow- movement of ice within a glacier when, under pressure, ice behaves as a plastic material
surface of a glacier
zone of fracture: the upper brittle part of a glacier where tension causes crevasses to form brittle ice
crevasses: deep crack in the brittle surface of a glacier
rate of glacial movement
can move up to several meters per day: surges= rapid movement
calving
wastage of a glacier that occurs when large pieces of ice break off
zone of accumlation
area where there is an accumulation of snow and ice
zone of wastage
area where there is a net loss to the glacier due to melting of carving
snowline
lower limit of snow accumulation, the elevation of the snowline can vary greatly
glacial budget
balance between accumulation a the upper and lower end
-advance: accumulation exceeds loss
-retreat: loss exceeds accumulation
-balance: approx the same
glacial erosion: role of meltwater
types
forms and refreezes because of pressure varaiation at the base of the glacier
plucking: lifting rocks by ice
abrasion: rocks within ice act like sandpaper
products of glacial abrasion
glacial polish-polished bedrock surface
glacial striations-grooves in the bedrock
rock flour-finely pulverized rock
glacial landforms
glacial trough
hanging valley
paternoster lakes
cirque
tarn
arete
hor
fjord
glacial deposits
glacial drift
till
stratified drift
tillite
varves
glacial erratics
drumlin
drumlin field
outwash plain
valley train
kettle holes
loess
moraines
layers or ridges of stony debris deposited along margins of or beneath a glacier
types of moraines
lateral moraine
medical moraine
terminal moraine
ground moraine
ice contact deposits
accumulationof stratified drift deposited by melt water flowing over within, or at the base of motionless ice
kame
steep sided hill created when stratified drift collects in openings within stagnant glacial ice
kame terrace
narrow terrace like mass of stratified drift deposited between glacier and adjacent valley
esker
sinuous ridge of stratified drift deposited by a stream flowing in a tunnel beneath a glacier near its terminus
glaciation effects
crustal subsidence and rebound results from the addition and removal of the immense weight of continental ice sheets
*sea level change
* drainage systems