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Tidewater Glaciers

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Title: Tidewater Glaciers


1
Tidewater Glaciers Glacial Landscapes Glacier
Bay
Chris Larsen, GI-UAF
2
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
3
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
4
Glacier Bay Isostatic Rebound
Chris Larsen, GI-UAF
1750
Today
5
Glacier Bay Isostatic Rebound
Chris Larsen, GI-UAF
6
Glacier Bay Isostatic Rebound
Chris Larsen, GI-UAF
Glacier Bay area andsurrounding parts of SE
Alaska rise by as much as 3 cm/year!
7
Glacier Bay Isostatic Rebound
Chris Larsen, GI-UAF
Glacier Bay area andsurrounding parts of SE
Alaska rise by as much as 3 cm/year!
8
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

9
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
10
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
11
Esker
12
Drumlin
13
Drumlin
14
Kettle holes
15
Kames
16
Glacial erosion Plucking, scratching etc.
Scratchmarks
17
Regelation
18
Larger erosional features Roches moutonnées
19
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
20
Glacial valleys
in contrast with river valleys, whichare
typically deeply incised (V-shaped), glacial
valleys have a flatter bottom withsteeper sides
(U-shape)
21
Glacial valleys
after complete melting of valley glaciers, the
tributary glaciers oftenleave behind hanging
valleys
22
Glacial valleys
after complete melting of valley glaciers, the
tributary glaciers oftenleave behind hanging
valleys
23
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
24
Lateral and medial moraines
25
Medial moraines and tributary glaciers
26
Ground moraine
27
Very old ground moraine
28
Terminal (end) moraine
29
Terminal (end) moraine Glacial lakes
30
Terminal (end) moraine Glacial lakes
31
Terminal (end) moraine Advance vs. retreat
32
Terminal (end) moraine Advance vs. retreat
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