Transcript Ice Ages

Ice Ages
Effects on Climate, Weather,
& Geography
Ice Age
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Referring to a long period of time in
the reduction of earth’s surface &
atmospheric temperature
Expansion of continental ice sheets &
polar ice
Large & Small Events
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We’ve had at least 4 large ice age
periods & dozens of smaller events.
The last ice age was approx 2.5 MYA
Advancing & retreating ice sheets
(glacial) generally occurs in cycles
every 40,000 to 100,000 years
Advancing & Retreating Ice
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Glacial is advancing ice
Interglacial is retreating ice
The last glacial period ended 10,000
years ago
Glacial Period
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Generally cooler drier climate over
much of the earth
Sea levels are lower due to water
retained as ice
Interglacial Period
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Earth has been in an interglacial
period for > 10,000 years
Climate warms
Glaciers form in places where the air
temperature never gets warm enough to
completely melt the snow. Over the years, the
snow becomes deeper as new snow falls.
Causes of Ice Ages
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Several factors including: alignment of the
planets / tilt of the earth / sun’s
gravitational pull on earth / wobble (spin
of the earth – because it is not completely
round)
Climate patterns influence glaciations,
including ocean currents.
All of this effects weather – which is
different from climate
On a 42,000 year cycle, the earth wobbles and the angle of the
axis, with respect to the plane of revolution around the sun, varies
between 22.1 – 24.5 degrees
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Earth’s Wobble
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Less of an angle than our current
23.45° means less seasonal
differences between the Northern and
Southern Hemispheres while a
greater angle means greater seasonal
differences (i.e. a warmer summer
and cooler winter).
Climate & Weather
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Climate is a given tolerance of
temperature & moisture in specific region
of earth measured over a given period of
time.
Weather is the day to day effects of
temperature / moisture in a given area.
Weather changes daily. Climate is a broad
range of temp & moisture over a long
period of time, with changes occurring
slowly.
Ice Age Meltdown – 20,000 YA
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Much of the Northern Hemisphere
was covered by ice sheets.
Threatened the survival of all living
things, including H. sapiens.
Ocean Currents & Climate Change
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Ocean currents are a primary source
of climate (heat / cold / moisture)
around the planet
There is an “ocean conveyor belt” of
cold & warm water flow (current)
within the oceans around the world.
{warm water rises / cold water sinks
AND fresh water rises / salt water
sinks}
During the Meltdown of the last Ice Age
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Fresh cold water runoff poured into the ocean
Instead of sinking, the fresh water (ice) is
lighter & stayed on ocean surface – preventing
the ocean conveyor system
Atmospheric Temp dropped 12 degrees in 20
years & created a mini-ice age {Younger Dryas
event}
Repeat Event
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This event occurred approx 6 times
between 18,000 – 8000 years ago,
with repeated climate shifts around
the world.
All living things needed to quickly
adapt to a constant changing climate
Climate Change – Geography Change
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Glacial ice from the last ice age was up to 2 miles
thick
25 % of the planet was covered in ice
Lower sea levels showed land bridges between
Siberia & Alaska / land between France & England /
Florida was much wider
When the ice melted – runoff created enormous
lakes / valleys / erosion of hill sides and numerous
geographic changes - 60,000 trillion tons of water
covered more of the earth than before the ice age
Sea level rose several hundred feet
Today
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Temperature has risen 10 degrees overall
since the last ice age
Sea level has risen 1 foot every century
We are in a global warming trend – not
the *“man-made” global warming
{*pollution}
With the addition of pollution {green
house gases-CO2}, melting ice caps can
change ocean currents & climate patterns
– creating another ice age sooner than the
natural cycle of change
The Future
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Before and after projection of parts
of Spain due to global warming.