Tidewater Glaciers

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Tidewater Glaciers Glacial Landscapes Glacier
Bay
Chris Larsen, GI-UAF
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Glacier Bay
Glaciers retreating in Glacier Bay Since first
recordings during Russian exploration in late
18th century Most of the retreat part of
natural advance-retreat cycle typical of
tide-water glaciers
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Glacier Bay
Glaciers retreating in Glacier Bay Since first
recordings during Russian exploration in late
18th century Most of the retreat part of
natural advance-retreat cycle typical of
tide-water glaciers
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Glacier Bay Isostatic Rebound
Chris Larsen, GI-UAF
1750
Today
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Glacier Bay Isostatic Rebound
Chris Larsen, GI-UAF
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Glacier Bay Isostatic Rebound
Chris Larsen, GI-UAF
Glacier Bay area andsurrounding parts of SE
Alaska rise by as much as 3 cm/year!
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Glacier Bay Isostatic Rebound
Chris Larsen, GI-UAF
Glacier Bay area andsurrounding parts of SE
Alaska rise by as much as 3 cm/year!
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GEOS120 Glaciers, volcanoes earthquakes

• Course outline
• 1. Introduction and overview
• - Glaciers What are they? Where do they occur?
  Why do we study them?
• 2. Ice, glaciers and landscapes
• - The building blocks of a glacier Snow, firn
  and ice
• - Anatomy and flow of a glacier
• - Glacier types
• - Ice sheets, ice streams and ice shelves
• - Periglacial phenomena and the glacial
  landscape
• 3. Ice ages and climate
• - Glaciation and the ice ages
• - Glaciers, ice sheets and global climate change
  
• - Ice cores as an archive of past climate

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Glacial deposits and the glacial landscape
Moraines - glacial landscape features composed of
till (i.e., rocks and sediments eroded and
deposited by glacier) U-shaped glacial
valleys Ground moraine blanket of sediments at
base of glacier Lateral moraine along sides of
glacier valley wall Medial moraine lateral
moraine displaced by tributary glacier
Terminal/end moraine build-up at terminus (end)
of glacier
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Glacial deposits and the glacial landscape
Sediment deposits - outwash plain built up by
melt-water deposition of sediments - kettle hole
left behind by melting detached pieces of ice -
esker long, winding, sandy ridge deposited at
glacier bottom - kame layered deposit of
sediment accumulating in voids such as between
glacier and valley wall - drumlin asymmetric
hill formed at base of glacier or ice sheet
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Esker
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Drumlin
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Drumlin
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Kettle holes
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Kames
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Glacial erosion Plucking, scratching etc.
Scratchmarks
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Regelation
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Larger erosional features Roches moutonnées
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Horns Aretes
Glaciers carving out cirques from mountain
eventually create a horn, with well
developedridges (aretes) separating the
hollowed-out faces of the mountain
Matterhorn, Switzerland
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Glacial valleys
in contrast with river valleys, whichare
typically deeply incised (V-shaped), glacial
valleys have a flatter bottom withsteeper sides
(U-shape)
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Glacial valleys
after complete melting of valley glaciers, the
tributary glaciers oftenleave behind hanging
valleys
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Glacial valleys
after complete melting of valley glaciers, the
tributary glaciers oftenleave behind hanging
valleys
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Till the stuff that moraines are made of
poorly sorted sediments (big boulders next to
sand grainsnext to clay) often highly
consolidated dueto ice load
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Lateral and medial moraines
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Medial moraines and tributary glaciers
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Ground moraine
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Very old ground moraine
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Terminal (end) moraine
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Terminal (end) moraine Glacial lakes
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Terminal (end) moraine Glacial lakes
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Terminal (end) moraine Advance vs. retreat
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Terminal (end) moraine Advance vs. retreat