The Ice Age

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The Ice Age
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Section Objectives

• Describe the climatic cycles that exist during an
  ice age.
• Identify and summarize the theory that best
  accounts for the ice ages.
• Climate during ice ages.
• Glacial periods.
• Cause of ice ages.

Ice age Internal plastic flow Kettle Lateral
moraine Medial moraine Meltwater Milankovitch
theory Outwash plain Roche moutonnee Snowfield Sno
wline stratified drift Terminal
moraine Till Valley glacier
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Climate During Ice Ages

• An ice age is thought to start when the average
  global temperatures are lowered.
• Studies show many cycles of advance and retreat
  of the continental ice sheets. Ice sheets advance
  during an ice age during glacial periods. Warmer
  temperatures in between glacial periods are
  called interglacial periods.

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Glacial Periods

• Glaciers cover nearly one-third of the earths
  land surfaces during one of the last glacial
  periods. Most of the glaciers were located in
  North America and Eurasia.
• Since most of the water in North America was
  locked up inside the ice the sea level was 140
  meters lower than it is today. Canada and some
  mountain regions in Alaska were completely buried
  in ice. Large ice sheets formed all over the
  world and later combined and moved around the
  world. Various land features that were formed by
  the last ice age are still visible today.

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Causes of Ice Age

• Scientists have many theories as of why the ice
  ages occurred. Each theory shows how the gradual
  cooling and increase of precipitation caused an
  expansion of the glaciers.
• A theory now widely accepted is the Milankovitvh
  theory. Milutin Mulankovitch said that small
  normal changes in the earths orbit and tilt
  caused the ice ages.
• There are three types of periodic changes that
  occur to changes the path in which the earth
  moves around the sun. One of these three changes
  happen once every 100 thousand years.
  Milankovitch was able to calculate these three
  periodic changes the distribution of solar energy
  reaching the earths surface. Evidence from the
  ocean floor inside dead marine animals shells
  proves his theory. Scientists have found that
  these animal shells closely follow the cycle of
  cooling and warming predicted by this theory.
• There are many other theories , which all portray
  the same idea, that the ice age resulted from a
  change in the amount of solar energy that touched
  the earths surface.

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Continued

• The explanations for some of these changes vary.
  Some theories say that these changes could have
  been caused by varying amounts of heat coming
  from the sun. Other theories say that volcanic
  dust blocked the suns rays from the earth etc

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The End
Or IS It?
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