Download New York`s Glacial Landscape

Glaciers and the Great Ice Ages
Pleistocene Epoch: the Great Ice Ages
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2.0 Ma to 10,000 years
ago
Four (or more) distinct
episodes expansion
and melting of ice
sheets (continental
glaciers)
Why did the climate change so
drastically and repeatedly?
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Climate change and
variations in Earth’s orbit
Eccentricity: elliptical to
nearly circular cycles
Obliquity: cyclic changes in
tilt of axis
Precession: cyclic change
in”wobble” of the axis
Variations affect amount
and distribution of solar
energy received by Earth
How does a glacier form?
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Cold climate is necessary
Annual snow accumulation is greater
than annual rate of melting
Snow builds up over time
Snow recrystallizes to ice
Glacial Flow
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Ice begins to flow
(plastic deformation)
under the influence
of gravity
Glacier = mass of
flowing ice
Glacial Flow
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Glacial Flow is constant
Some parts of glacier are
melting
Rate of accumulation vs.
rate of melting determines
if glacier will advance or if
end of glacier will melt
back (glaciers never flow
backwards)
Glaciers and Landscapes
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Flowing ice picks up
sediment, soil, etc.
Breaks loose pieces of
bedrock
Modifies landscape by
erosion and
deposition
Erosion by Glaciers
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Striations: “scratch”marks made as ice drags
rocks across bedrock
Erosion by Glaciers
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Modifies “V” shaped river valleys to a “U”
shape
Deposition by Glaciers
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Erratics – pieces of
“exotic” rock left by
glacier
Till – unsorted,
unstratified sediments
dumped by ice
Outwash – sorted and
stratified sand and gravel
deposited by meltwater
Deposition by glaciers
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Lacustrine sediments
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Lakes form between melting edge of ice and
obstructions (often deposits of till)
Fine silt and clay settle in calm water
Clay may be used in pottery and brick making
If lakes drain or fill with sediment:
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bogs and swamps – ecologically important wetlands
Water-logged lacustrine sediments may cause tilting
and sinking of buildings constructed on them
Glaciers and Landforms
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Characteristic
landforms
New York’s Glacial Landscape
Shaped by Erosion
and Deposition
Glaciers and New York’s Landscape
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Great Lakes – Erie and Ontario
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Finger Lakes
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Glacially widened and deepened E-W stream valleys
Glacially deepened N-S stream valleys
Mohawk Valley – “misfit” stream
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Glacially widened and deepened E-W stream valley
Glacial Lake Albany – drained when ice left Hudson
Valley
Glaciers and New York’s Landscape
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Susquehanna Valley
modified to U shape
Dammed by till at
Wells Bridge (near
Otego)
Dam broke and lake
drained
Glaciers and New York’s
Landscape
 Hudson Valley – a fjord
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Glacially deepened N-S
stream valley
Flooded when sea level
rose
Salt water as far north as
Poughkeepsie
Tides affect river level as
far north as Troy
Ocean freighters can sail
up to Albany – an inland
seaport
Kensett’s Hudson - Fjord
Palisades (igneous rock) along
the Hudson Fjord
Hudson Fjord, Long Island Sound,
Moraines and Outwash of Long Island
Glaciers and New York’s Landscape
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Long Island
Two terminal
moraines
Outwash plain
Long Island Sound Glacially widened
stream valley
flooded by rising sea
level
Other Glacial Features
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Outwash channels – Niagara River
“Hanging” valleys and waterfalls – very
prominent in the Finger Lakes
Kettle lakes
Drumlins
Church’s Niagara Falls –
Outwash Channel
Glaciers and New York’s Economy
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Thick, fertile soils developed on till and
outwash – foundation of agriculture in
state
Microclimate associated with Lakes
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Water moderates climate
Warmer in winter, cooler in summer
Ideal for growing grapes/producing wine
Aquifers – especially in outwash
Sand and gravel for construction