Earth Sciences 1022A/B Lecture Notes - Lecture 17: Plate Tectonics, Global Cooling, Continental Drift
10 Jan 2017
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Document Summary
Glaciers form by compaction, re crystallization of snow eventually turns into ice. Ice sheet are radial spreading large ice masses on continents (e. g. antarctica) Valley in mountains, commonly flow down old stream valleys. An upper brittle zone of fracture (50 m thick) rides on a lower zone of plastic flow. The glacier may also slide over its bed. Budget of a glacier involves two zones of accumulation (gain of snow and ice) and ablation (wastage or loss by melting, evaporation, icebergs calving in water (i. e. breaking off the glacier)) If accumulation > ablation, the glacier terminus commonly advances. If accumulation < ablation, its terminus usually retreats. Internal movement within a glacier is always toward the front, even during retreat. Occurs by plucking (freeze on of loose bedrock); and abrasion (using the glacier load to scrape, scour, gouge the sub glacial floor and sides) Striations (scratches) and grooves form by particles in ice scraping over bedrock.
