Glaciers
An Introduction to a Powerful Force
That Has Shaped the Earth.
Glaciers Have Sculpted the Earth
Around You….
How Do Glaciers Shape the Earth?
What Is a Glacier?
• A mass of moving
ice created from
accumulation of
snow over many
years that
compresses into
large, thickened
ice masses
• A glacier moves
like a very slow
river eroding and
shaping the land
beneath it
What’s important about Glaciers?
• Glaciers are the second largest reservoir of
water on earth.
o
• A 5 C increase in global average temperature
would likely cause all glaciers to melt, raising
sea level by 50-70 m.
• Glaciers represent permanent ice (does not
melt each summer) - so they reflect climatic
conditions, not variations in weather.
What’s important about Glaciers?
• Glaciers are an important agent of erosion
and formed much of the landscape of
Michigan.
• Form deposits of sediment that have
distinctive characteristics (drift and till).
• Most recent glacial period culminated at the
end of the Pleistocene, about 15,000-20,000
years ago.
How do Glaciers form?
• Starts with abundant winter snowfall that
doesn’t melt away (snowline - altitude above
which snow is permanent)
• Snow is converted to glacial ice under
overlying weight of accumulating snow
• 2 Major requirements:
– Low Temperatures
– Adequate amounts of snow
FIRN
• Grainy ice
created from
the partial
melting and
refreezing of
snow crystals.
Requirements for
Glacier
Formation:
•Temperatures low
enough to retain snow
year round (High
Altitude and High
Latitude).
•Sufficient Snow: Some
polar climates are very
dry, so glaciers do not
•develop.
A Brief Overview of Glacier Formation
• Select this button to
access the story of a
Glacier….
Loading the web site may take a
moment, please be patient….
Types of Glaciers
Categorized by:
• Size
• Where they
formed
Two Types:
• Valley Glacier
• Continental
Glacier or Ice
Sheet
VALLEY GLACIER
• A Glacier formed
in mountainous
areas when ice
moves down a
valley. It
produces a long,
narrow, wedgeshaped mass of
ice.
Continental Glacier
Ice Sheets
• A Glacier covering a
large land mass
(millions of square kilometers).
The type of Glacier
occurring during the
ice age and in
present day
Greenland and
Antarctica.
Movement of Glaciers
• When ice accumulation is thick enough it will
begin to flow.
• Speed and Amount of flow depends on slope
and weight.
• Two Movement Types:
– Basal Slip
– Internal Plastic Flow
Basal Slip
• The weight of overlying ice exerts enough
pressure to melt some ice at the base of the
glacier.
• The melting ice creates a slippery surface for
the overlying glacier to slide over.
Internal Plastic Flow
• Solid ice crystals throughout the glacier
slipping over each other
• Creates a slow forward motion
• Like a river, not all parts of the glacier flows
at the same speed. Where would it flow
fastest? Slowest? And Why?
Valley Glacier
Landforms
Cirque and Aretes
Cirque
• A bowl shaped
depression
Aretes ‘Spine’
• Sharp, jagged
ridges between
cirque
Horn
•Several Aretes joined to form a
sharp, pyramid peak
Hanging Valley
• A small tributary
glacial valley
suspended on a
higher portion of
a mountain.
• Ice melt flows
over the cliff as a
waterfall.
U-Shaped Valley
• As the valley
walls and floor
are scraped
away by a
glacier, the
original V-shape
valley is
changed into a
U-shape.
Moraine
• Landforms
made from
glacial till
Photo depicts a ground moraine.
•Ridges of unsorted rock material on
the ground or on the glacier
Lateral Moraines
• Strips of dirt
and rock that
flow with the
ice along the
sides of valley
glaciers.
Medial Moraines
• When a segment
of the glacier
merges into a
larger ice mass,
the lateral
moraines create
debris in the
middle of the
larger flow.
Continental Glacier
Landforms
• Erode by leveling existing landforms,
producing relatively smooth, rounded
landscapes.
• Features are exposed as the glacier
retreats.
Moraine
• Landforms
made from
glacial till
Photo depicts a ground moraine.
•Ridges of unsorted rock material on
the ground or on the glacier
Ground Moraine
• A mantle of till
deposited
underneath the
ice
• Often very
rocky
Ground Moraine
• Farmers and
people putting
in a new yard
uncover the
many rocks
deposited from
the last ice
The soil of Ohio west to Montana
and age.
North
to Canada is ground moraine
Terminal Moraine
• Hilly ridges
composed of a
mixture of rock,
sand, and clay
• Marks the
farthest
•Cape Cod and Long advance of the
Island are examples of ice.
Terminal Moraines
Till
• The result of
glacial drift
• Contain various
sizes of sediment
that is not sorted
or layered
Outwash
• Glacial till that
has been
transported,
sorted and
deposited by
glacial
meltwater
Kame
• Small hills of
sand and
gravel
• Formed from
outwash.
Esker
• Long, narrow ridges
of sand and gravel in
the middle of ground
moraine
•Form from melt water
streams flowing in tunnels
along the bottom of the
melting glacier.
• They wind for
kilometers roughly
parallel to the
direction the ice
moved.
Gravel Pits
• Today, Kames
and Eskers
created
during the
last ice age
are frequently
exploited as
gravel pits.
Erratic
• A large boulder
deposited by a
glacier.
• Typically a different
rock type than the
material in which it
is deposited.
Kettle
A Kettle Lake
• The result of a
very large block
of ice being left
behind as a
glacier recedes.
The melting ice
forms potholes
which are
sometimes filled
with water in a
glacier, till, or
outwash plain.
Vegetation may
grow up around
kettles.
Drumlins
• Long, low, tear
shaped mounds
of till
Drumlins
have the
shape of an
inverted
spoon
• The long axes of
the drumlins are
parallel to the
direction of glacial
movement
Roches Moutonnees
• Rounded knobs
of rock created
by a glacier
• The glacier
polishes and
smooths out
the top of
The glacier plucks chunks of
existing rock as
the rock out as it passes by
creating a rough surface on the it passes over
side
Dangers of Glaciers
Icebergs
Crevasses
Iceberg• Pieces of ice that
break off of a
glacier.
• The ice sheet on
Greenland is the
primary source of
icebergs in the
North Atlantic.
• Create a hazard for
ships.
Crevasses
• Large cracks
formed in the
surface of a
glacier
• Often covered
with snow and
extending 30 m
downward
The Ice Age
• A long period of
climatic cooling
during which
continental ice
sheets cover
large areas of
the earth’s
surface.
The Ice Age
• It is believed that
the world has
gone through
several periods of
glacial ice age
advancement and
retreat.
• It will occur
again….
Causes for an Ice Age
Milankovitch
Theory
• Small, regular
changes in earth’s
orbit and tilt
which cause
changes in the
amount of solar
energy reaching
earth’s surface
Causes for an Ice Age
3 Periodic Changes
Milankovitch
Theory
• A more elliptical orbit
• Tilt ranging from 21.50 24.50
• Circular motion of
precession
Useful web sites for Glaciers
http://www.asf.alaska.edu:2222/how_form/glacier_form_begin.
html
http://www.uwsp.edu/geo/faculty/lemke/alpine_glacial_glossary
http://www.davison.k12.mi.us/bentley/glaciers.html
http://nsidc.org/glaciers/story/page1.html
http://wrgis.wr.usgs.gov/docs/parks/glacier/uvalley.html
www.nps.gov/olym/edglac.html
http://www.eoascientific.com/interactive/glaciers/glaciers.html