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Erosion &
Deposition by Ice
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2 Types of Glaciers
• Continental
– Cover large areas, like continents
– Due to cold global climates
• Alpine
– Cover mountain tops and sides
– Due to Orographic effect
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GLACIERS - VALLEY AND CONTINENTAL
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Glaciers
• Form when snow accumulation is
greater than snow melting
– Cause a build up of ice
• Glacial movement is similar to streams
(fastest in center)
• Create "U" shaped valleys with nearly
vertical walls and flat bottom
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Glaciers in North America
over the past 2.0 x 106 years
• Ice covered most of New York several
times in the “recent” past
• Most recently about 11,000 – 15,000
ybp.
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The last major glacial period
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Erosion by Glaciers
• Glaciers remove and carry sediments
– Ice can be thousands of feet thick and thus
very powerful.
– Surface materials (like soil) are easily
removed.
– Sediments at the bottom of the ice act like
sandpaper and scour the bedrock.
• Continental and alpine glaciers have different
erosional (and depositional) characteristics.
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Glaciers
• Create features like striations
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Glaciers
….glacial polish
–Where
rocks within
a glacier
grind
against
bedrock
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Deposition by Glaciers
• Mixed sized sediment drops
vertically as glacier melts
–Unsorted sedimentation
–Sediments often scratched
(striations)
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Glacial Deposition
• This
sediment
is made
of a
variety of
particle
sizes
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Deposition by Glaciers
• The large rocks
left behind by
glaciers are
called glacial
erratics
– Large rocks not
broken into small
particles
– Often different in
composition than
the bedrock
upon which they
sit
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NY Erratic
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Erratics in our area

Based on this
image, where did
the erratics and
other non -native
rock in Harpursville
come from?
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Deposition by Glaciers
• Glacial till
– Unsorted glacial sediment
• Ranges from clay sized particles to boulders
– stratified (sorted) sediment consists of
glacial sediments carried by meltwater and
deposited in an outwash plain
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Till- Sierra Nevadas
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• A wide variety of landscape features are
created by glaciation
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These features are most often associated with alpine
glaciations:
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Drumlin-Cranes Beach MA
• Drumlins- Oval
shaped Moraine
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Esker-MN
• Esker- Rivers on ice
bore a hole in the
ice and flow under
the sheet. Rocky
material builds up
and the stream bed
is left behind as a
ridge of rubble.
Esker-WI—Note boulders
carries by water
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Esker- NE WA
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Kettles- Large block of ice separates and
becomes surrounded with debris
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 How is a valley created by a
glacier similar to and different from a
valley created by a stream?
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U Shaped Valleys- Yosemite
Valley-
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Hanging Valley- Yosemite Natl
Park, CA
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Holgate Glacier
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Glaciers Fusing Yukon Canada
Terminus
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Iceberg Calving
Terminus
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Portimoreino
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Jones Beach NY is part of an
outwash plain
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Glaciers Video Awsome!
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