GEOL-1010 Lecture Notes - Lecture 14: Isostatic Depression, Sea Level Rise, Thermohaline Circulation

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5 Feb 2018
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Geology 1010
Lecture 14 Glaciers
4/11/2017
Geology in the news:
Permafrost stays frozen year round thawing in Canada is so extensive it’s changing the
landscape all the way to the coastlines.
Google earth of Canada is showing changes all the way across Canada not just where the
permafrost is located.
Effects of Glaciers
Sea level change
Melt all glaciers = sea level rise of ~ 65 m (~200ft)
(Flooded almost all of Florida and up the coast line)
)f melting continues to completion, that’s how much flooding you will have to deal with.
Glaciers and sea level changes
o Glaciers trap huge amounts of water.
o As the melt and expand they dramatically change the amount of sea level.
Coastline during the ice age
o Light blue = above water (look at map)
Isostatic depression adding enough weight to the material that everything in the median
begins to sink.
E. Antarctic ice sheet has caused up to 2.5 km of isostatic depression.
o Ex. Glacier -> crust subsidence moves downward
Isostatic rebound (opposite) crust tries to return to its normal elevation
o Ex. Crust rebound, upward movement
Alters thermohaline circulation, big effects on ocean circulation patterns
Drinking water & irrigation
Ex. Washington gets ~ 470 billion gallons/yr
*Study Hint*
o Melting glaciers do not provide MORE drinking water
o The glacier gets smaller every year, so there is less and less ice to melt.
Glaciers Basics
Glacier has to be in motion (similar to a sand dune)
Ice on earth
o Currently covers ~9% of Earth’s land area
Antarctica (85%)
Greenland (10%)
5% is spread around the world
o Ice on Antarctica exceeds 4,200 m (2.5 miles) in max thickness
Forming a glacier
o 1 - Start out with basic snowflake
o 2 granular snow (more compacted)
o 3 firn (denser more compact form)
o 4 Glacial ice (different from every day ice, has a different density)
o minimum of 50meters in thickness to be considered a glacier
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o *Requires time, cold, and precipitation*
o
Types of Glaciers
o Valley Glaciers
Aka Mountain, alpine
You can find them all over the world.
Ex. Mt Kilmanjar (Africa; ca 20,000Ft)
Located right on the equator, do not have to be in Antarctica or Greenland to
study glaciers.
o Continental Glacier
Aka ice sheet
Really large
Buries everything on the landscape
o Glacial Advance and Retreat
Accumulation temperature is cooler, bigger area that collects more snow/ice
Ablation warmer, harder to add material to the glacier, lost some ice.
Firn Line equilibrium line, add two inches a year and you melt two inches a
year. Important to know where this line is at.
Ex. Valley glacier
o Glacial movement
Speed varies
Different sections of the glaciers move at different speed.
Due to friction
Ice closer to the valley walls experience more friction than the ice
located in the middle.
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