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Glaciers (chapter 11 in Summerfield)
• Permanent (on human timescales) body of ice, consisting largely of recrystallized snow, that shows evidence of downslope or outward movement due to pull of gravity.
• ~10% of surface of continents covered by ice today, but ~30% covered as little as ~18,000 years ago (landforms, sediments, isostasy, climate records)
• Glaciers responsible for huge amounts of erosion in high-elevation terrain (although processes tough to observe, poorly understood)
Glaciers (chapter 11 in Summerfield)
• Form depends on competition between accumulation and melting of ice
• Snow accumulates and compacts to form ice, but ice doesn’t sit still… it deforms plastically
(handout)
Types of glaciers
(1) Temperate vs. Polar
(2) Alpine or mountain glaciers• Valley glaciers• Cirque glaciers• Fjord glaciers
Ice caps or ice sheets or continental glaciers• Today, only Greenland and Antarctica• Their combined mass is 95% of ice on Earth• Melt would cause 200 ft sea level rise• Can have ice shelves (floating ice at coast)
Glacial Deposits
Glacial outwash - sediment choked streams from melting glacier form braided streams, deposit poorly sorted, stratified sediment
Iceland
What processes link climate change, glaciers & sea level?
Eastern Juan de Fuca Strait was filled with ice prior to 13,000 years ago (13 ka). The area was isostatically depressed.
When climate warmed and the ice melted ~12 ka, how did local RELATIVE SEA LEVEL change?
time
local sea level
Relative sea level curve, Juan de Fuca Strait (Mosher et al., 2004) Global eustatic sea level curves (Fairbanks, 1989; Peltier, 2002)
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