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GEG 120
Peter Muller

GLACIAL DEGRADATIONAL AND AGGRADATION INTRODUCTION TO GLACIAL GEOMORPHOLOGY -Cryosphere: all forms of frozen water in the vicinity n Earth's surface -All types of glaciers and snow cover -Ice Floating atop water bodies -Permanently frozen ground (permafrost) -Our focus is on glaciers as powerful agents of landscape transformation -High latitude and high altitude regions -Degradational landforms -Aggradational landforms -Glacier: body of ice, formed on land that is in motion (they do not move but very slowly and not easy to observe) TWO MAJOR CATEGORIES OF GLACIERS -Mountain (Alpine) Glaciers -Confined in valleys -Very steep slopes -Alaska and Switzerland Alps -Continental Glaciers (Ice Sheets) -Huge masses of unconfined ice -Bury entire country sides -Slowest-moving glaciers -Antarctica and Greenland GLACIERS OF THE PAST -Yield valuable evidence of environmental dynamics -Past ad Preset climate change (Units 20) Accompanying rise and fall of global sea levels -Geographic hallmarks of earths periodic ice ages -Lowered global temperatures trigger expansion of glacial expansion in higher latitudes and high altitudes everywhere -Can endure for millions of year -Marked by alternating cooling and warming stages Glaciation- cooler period of ice expansion (continental and alpine) -Deglaciation: warmer period of ice contraction -Interglacial period of warmer worldwide temps between the last deglaciation and the onset of the next glaciation WHAT CAUSES ICE AGES -Many questions about periodicity and terrestrial vs. solar-system conditions - but no scientific consensus -Seven current theories -Continental drift towards higher latitudes -Coastal bulging from plate collisions -Global impacts of volcanic activity -Variation in greenhouse gases -Large-scale expansion and contraction of vegetation -changing oceanic circulation (North Atlantic Drift) -Earth-sun dynamics (eg fluctuations) fluctuations FFORMATION OF GLACIAL ICE -Glacial Ice: compacted, recrystalized snow -forms where snowpack does not melt in warm season (as above the snow line in high mountain zones) -That snow is slowly converted into ice in stages FLAKE -> FIRN (weeks) Firn: (granular, compacted, old snow) undergoes compression and recrystallization that slowly squeezes at the open spaces between THE GLACIER AS A SYSTEM -Open system -Input (precipitation {snow}) -Output (melting and evaporation) Gain: new snow added in its upper zone of accumulation Loss: melting/evaporation in lower zone of ablatio
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