Earth Sciences 1022A/B Lecture Notes - Lecture 10: Glacier Terminus, Continental Drift, Global Cooling
14 Jan 2016
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Document Summary
Glaciers: form by compaction, re-crystallization of snow that eventually turns into ice. Ice sheets that are radial-spreading large ice masses on continents (e. g. antarctica) Valley: continental scale, radial flow from a central area, in mountains, commonly flow down old stream valleys by gravity. Movement of a glacier: cm/day is normal; an upper brittle zone of fracture ~50m thick rides on a lower zone of plastic flow; the glacier may also slide over its bed. Internal movement within a glacier is always toward the front, even during retreat commonly advances. Glacial erosion: occurs by plucking (freeze-on of loose bedrock); and abrasion (using the glacier"s load to scrape, scour, gouge the subglacial floor and sides), results in striations, grooves on rock. Striations (scratches) and grooves form by particles in ice scraping over bedrock. Glaciated valley (u-shaped) become fjords along coasts; Ar tes (sharp ridges) and horns (pyramid-shaped peaks) form where multiple cirque glaciers gnaw into a mountain divide from the sides.
