X1011584164-00079-19937</DOCNO> Glaciers Geology 1001-section 4 Dr. Dutrow (c) Partial version of overheads Back to Syllabus last updated: 4/01/98 GLACIERS AND GLACIATION Glaciers - a permanent body of recrystallized snow moving due to Found at high landbound ice in motion Mountain glaciers (Alpine) - shape and direction of movement are a function of Cirque glacier - Valley glacier - fills Fjord glacier - occupies Piedmont glacier - broad bowl-shaped glacier Ice cap - covers a Rock glacier - composed of Ice sheets (Continental) - continental-sized Ice shelves - mass of (Note: loss of ice sheets would raise sea level ) General glacier classification based on relative T - controls Temperate (wet) glacier - at the higher pressure of the base of the glacier the temperature characterized by a Polar (dry, cold) glacier - at the higher pressures of the base of the glacier characterized by a Glaciers form from: Conversion of snow to glacial ice - glaciers are with burial, snow - Change in glacier size - Glacial Budget: matter of mass balance - if accumulation exceeds ablation generally activity at the terminus calving forms Glacial Movement Ice moves and carries objects by Maximum velocities at the Typical rates of movement is a Glacier surge - unusually Glaciation - the modification of the land surface by Glacial erosion and sculpture - due to high viscosity and P of ice Erosive features (abrasion) Glacial Striations Scratches from rocks frozen in base of glacier Glacial grooves and polishing Linear depressions or polish due to rocks and fine sand in base of glacier Glaciated mountain landforms Cirques Bowl-like form caused by frost-wedging, plucking and abrasion Tarn Small lake in a cirque Arete Knife-like ridge that forms as 2 cirques erode headward Horn Point that forms as >2 cirques erode headward Glacial Valleys (hanging valleys) U-shaped valley formed from glacial erosion Fjords Valley carved below sea level on the coast Landforms from ice caps Glacial striations Scratches in rock that can indicate direction to center of ice cap Drumlins Streamlined hill, gentle upstream, but steep downstream, depositional and erosional character Transport by glaciers Load is Load tends to be concentrated along Much of the basal load is Glacial Deposits Extremely efficient agent of Collectively called Generally Ice-laid deposits Till - unsorted drift Tillite - lithified till Glacial erratic - rock different from Moraine - deposits with form Ground moraine - widespread drift Terminal moraine - ridge-like accumulations at Lateral moraine - ridge-like accumulations of along (100's feet high) Medial moraine - ridge-like accumulation at Stratified drift - deposits in Outwash - stratified sed deposited in Esker - sinous deposit of due to Deposits with Kame - small hill Kettle - small basin Permafrost - permanently frozen Glacial Ages Louis Agassiz (1837) - hypothesis of continental glaciation - dramatic evidence for Ice Age Glaciers During the Cenozoic the global climate has In the last few million years there are numerous 30,000 years ago 29% of the land lowering of deform the crust due earlier glaciations deep sea records indicate Early and late Early and late\ Little Ice Ages = Causes of Glaciations Interaction of atmosphere, earth, oceans, biosphere and sun Glacier ages relate to Movement of continents Large scale Creation of The boiling point of water is the temperature at which it changes from a liquid to a gas.
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