Glaciers
➔ Types:
1. Valley Glaciers
2. Continental Glaciers
Glaciers
➔ Valley Glaciers
aka, Alpine Glaciers: Glaciers found high in
mountain valleys, above the snow-line, that move
downward through the valleys.
Example: Glacier National Park in Montana
➔ Continental Glaciers
aka. ice fields or ice sheet: Glaciers made from large ice
sheets that cover relatively flat ground that flows outward from
where the greatest amounts of snow and ice accumulate.
Greenland’s Continental Glaciers thickness is more than 3000 meters (10,000ft)
and depresses the bedrock below sea level.
Origin/Formation of Glacial Ice
Glaciers form only on land…
water is too warm for glacier
formation.
Firn: Like
packed
snowballs
Why do glaciers form
in the mountains?
Today:
● Glaciers cover about 10% of the land surface on Earth
● In Earth's recent history, glaciers covered as much as
30% of the land surface.
Scientists’ detective work:
● Signs of Glaciers in the past
○ Observe ways the land has been eroded
○ Look at deposits that have been left behind
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Discover the different erosional features formed by alpine glaciers.
Discover the processes by which glaciers change the underlying rocks.
Discover the sorting and types of particles deposited by glaciers as they
advance and recede.
Discover the landforms created by glacial deposits.
Fastest
Glacial Movement
Plastic flow … from ice
pressure
Glacial slip -- glacier slides
over underlying surface.
Movement: factors: 1. amount of ice in field, 2. steepness of the slope,
3. roughness of the ground surface
Where pressure is so great … undergoes plastic flow where lubricated by water
at bottom due to melting.
Erosion from Glacier movement:
abrasion
Scraping of the
underlying bedrock,
produced as ice flows
against it.
plucking
Removal of blocks of
underlying bedrock by
the glacier as meltwater
seeps into cracks and
freezes.
Movement: factors: 1. amount of
ice in field, 2. steepness of the slope, 3.
roughness of the ground surface
Where pressure is so great … undergoes
plastic flow where lubricated by water at
bottom due to melting.
• As a glacier moves, rocks that are stuck in
the ice are dragged across the exposed
bedrock. This causes deep scratches and
gouges in the bedrock called striations
• The direction of the striations shows the
path of movement of the glacier
There were 2 periods of glaciations here. Can you tell
which was first? Which directions did the 2 glaciers
move?
Glacier movement creates landforms by
weathering and deposition:
1. Abrasion
2. Plucking
3. Bulldozing… Movement of large boulders that have
been transported into the area by the glacier… often
different in mineral composition than the bedrock of the
area.
Boulder in Yellowstone
National Park:
6 Feet tall.
Glacial Erosion by valley glaciers creates various
landform features:
“U” Shaped
valleys : in
Glacier
National Park
Glacial Erosion by valley glaciers creates various
landform features:
Hanging Valleys:
with smaller glaciers
meeting and creating
river water that
cascades down steep
valley walls forming
waterfalls
Bridalveil Falls in
Hanging Valley
Glacial Erosion by valley glaciers creates various
landform features:
cirque
Steep-sided, bowl-shaped
depression formed as a
glacier plucks and erodes
underlying bedrock.
Glacial Erosion by valley glaciers creates various
landform features:
horn
Sharp-sided,
angular peak
formed as glaciers
move away from a
central peak.
The Matterhorn in Switzerland is the
most famous example of this type of
erosion
Glacial Erosion by valley glaciers creates various
landform features:
arête
Steep-sided,
sharp-edged ridge that
forms as two glaciers
erode in opposite
directions.
Glacial Erosion by valley glaciers creates various
landform features:
roche moutonnée
Asymmetrical hill of bedrock formed by abrasion
and plucking of the moving glacier.
Glacial Erosion by valley glaciers creates various
landform features:
roche moutonnée
Asymmetrical hill of bedrock formed by abrasion
and plucking of the moving glacier.
Arête
Cirque
U-Shaped
Valley
Arête
Horn
Moraines
Deposition by Glaciers
Depositional Features of Glaciers:
glacial till
Any unsorted deposit of sediment deposited by
glacial ice.
Glacial till - unsorted
Glacial till forms when glaciers melt more
than they flow forward… The melted glaciers
deposit all the big and small bits of rocky
material they have been carrying.
Depositional Features of Glaciers:
Moraines: Deposit of unsorted, rocky material on, under
or left behind by glacial ice.
Lateral moraine: rocky material at the edge of a glacier.
Medial moraine: where two glaciers join together… forming in
the middle of a glacier.
Depositional Features of Glaciers:
Depositional Features of Glaciers:
Terminal moraine
Unsorted pile of glacial
till that marks the
furthest reach of a
glacier's advance.
Depositional Features of Glaciers:
ground moraine
Thick layer of sediment deposited under a flowing glacier.
Depositional Features of Glaciers:
drumlin
An asymmetrical hill formed from sediments under the flowing glacier.
esker
Long, curving, upside-down 'V' shaped ridge of sediment deposited under a
glacier by meltwater.
Outwash plain
Broad band area of stratified drift blankets the region just beyond the furtherest
reach of the glacier, as meltwater streams spread material outward
Depositional Features of Glaciers:
Kettle Lake
Drumlins
n
i
a
l
p
h
Esker
s
a
w
Till
Moraine-dammed lake
t
u
O
Terminal Moraine
Glacial Stream
Drumlins- long, smooth hills made of glacial till.
- formed when a glacier runs over a moraine
made by a previous glacier, “smearing” it out.
- The drumlin points in the direction that the
glacier is moving
drumlins
Outwash Plains- melt water from the bottom
of the glacier carries sorted sediment out in
front of the glacier
Outwash Plain
Kettles- circular lakes. Chunks of ice often break off
the glacier and are buried in the ground by sediment.
As the buried ice melts, the sediment sinks into the
hole and the water fills it up
Another type of lake, found in New York, is called
a moraine-dammed lake. This is formed when a
glacial moraine blocks a river valley from draining.
The river floods the valley and forms a long,
narrow lake.
Ex. the Finger Lakes in upstate New York.
Depositional Features of Glaciers:
• The tremendous weight of these glaciers causes it
to slowly move outward from the center (some
only moving centimeters per year)
• When the glacier reaches the sea, chunks break
off and become icebergs (this is called calving)
• *Smaller ice sheets are called ice caps
➢ GREENLAND: 1.7 Million SQ MI , 3 KM thick
➢ ANTARCTIC: 12.5 Million SQ MI, 5 KM thick
Interrelationships to
Earth’s Systems
Important in understanding global scale climate
changes since related to 5 of Earth’s systems:
1.
Exosphere (outermost region of plant’s atmosphere)…
regulates sunlight exposure
2.
Hydrosphere (water on Earth’s surface)
glacial ice is frozen water
3.
Geosphere (Lithosphere, hydrosphere, and atmosphere) glacial
ice flow modifies landscape
4.
Atmosphere (gases surrounding Earth) … regulates global
atmospheric patterns and temperatures
5.
Biosphere (animal and plants)