Glaciers

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Glaciers
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What is a Glacier?
A large mass of compacted snow and ice that moves
under the force of gravity.

• Quick Facts
• 10 of land area is covered with glaciers (32
  during last ice age)
• Store about 75 of worlds fresh water (if all
  melted, sea level would rise 70 meters world
  wide)
• Glacial ice is blue because of density -white
  glaciers have air bubbles
• 90 of an ice berg is under water
• North Americas longest glacier is the Bering
  Glacier in Alaska.

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Where do Glaciers form?
Areas where more snow fall than melts each year
The lowest elevation at which permanent snow
occurs in the summer is called THE SNOW LINE. The
snow line is not the same for all places at a
given latitude.
Most are located in Antarctica and Greenland, but
most continent have them even Africa (10).
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Glacier Types
Valley A glacier that moves within valley
wall (Known also as Alpine Glaciers) EXAMPLES Mu
ldrow Glacier in Denali National Park, Alaska,
Alps, Himalayas, Alaska
Continental A glacier that covers a large part
of a continent. (sometimes called Ice
Caps) EXAMPLES Antarctic, Greenland, Iceland,
Baffin Island, Spitsbergen large island in
Arctic Ocean
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Icebergs When great blocks of glacier breaks off
into the sea.
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How do Glaciers Move?
Gravity
Basal Slip weight causes melting at the base /
this reduces friction allowing the mass of ice to
slide under influence of gravity.
Plastic flow ice on the interior of the glacier
changes shape under the pressure / the bottom
grains are almost flat allowing them to slip past
each other.
Ice Front Glaciers periodically retreat or
advance depending on the snow accumulation each
year. Heavy snows increase pressure on bottom
ise glacier moves faster than normal.
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Glacial Features
Cirques Iceberg Lake, Glacier National Park,
Montana
Aretes
Horn Mount Assiniboine, Canadian Rockies
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Glacial Evidences
Till rock material that is deposited by
retreating glaciers.
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Glacial Evidences
Lateral
terminal
Moraines An accumulation of glacial till.
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Glacial Evidences
Striations Coarse sand, pebbles sharp
boulders scratch the rock below. The scratches
are usually parallel and show the general
direction of the ice movement
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Plucking Blocks of rock are separated from
rocky surface and carried off.
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Plucking out rocks
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Glacial Evidences
Glacial Valleys This is a U-shaped valley with
a smooth floor and nearly vertical walls.
Teton Range, Wyoming
Franconia Notch, New Hampshire
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Glacial Evidences
Cirque A basin that can be found at the head of
a valley glacial. Once melted the cirque might
become a lake. (example Lake Louise in Canadian
Rockies)
Hanging Valleys These are side valleys that
plunge to a main U-shaped valley creating water
falls. (examples Bridalveil Fall in
California.)
Gunsight Pass along the Continental Divide.
Lake Ellen Wilson tumbles over 1,500 feet down
Beaver Chief Falls into Lincoln Lake.
Yosemite National Park
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Glacial Deposits
Outwash Materials deposited by glacier melt
water. Outwash plains a broad flat area.
Erratics Large boulders that have been
transported into an area by a glacier and have a
different composition that the bedrock of that
area.
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Glacial Deposits
Drumlins These are long, smooth, tear shaped
mounds. They are usually found in groups and
point in the direction of glacial movement.
(common in Wisconsin central New York)
Cato, New York
Near Calgary, Canada
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Glacial Deposits
Eskers Subglacial streams that form in winding
tunnels. The tunnels become filled with sand and
gravel. When the glacier melts the deposits
slump down and form long winding ridges. (common
in Mississippi Valley, New York and Maine)
Waterford, Maine
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Glacial Miscellanous
Tarns Where river valleys are blocked by
moraines forming long narrow lakes. (examples -
Lake George the Finger Lakes in New York)
Kettle Kettle Lakes Bowl shaped hollows where
buried blocks of ice melt. Often they become
filled with rainwater forming lakes. (common in
Minnesota, Michigan, Wisconsin, New York and New
England.)