Glaciers

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Glaciers
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Glaciers

• Thick masses of ice that glide slowly across our
  planets surface
• Two types of glaciers
• Sheet Glaciers
• Mountain Glaciers

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Sheet Glaciers

• Form when snow accumulates over tens to hundreds
  of years
• The snow eventually becomes so thick/heavy that
  it collapses under its own weight
• This forms dense glacial ice
• When enough ice is compacted it succumbs to
  gravity and begins to flow downhill or spread out
  across flat lands.
• What makes glaciers unique is their ability to
  move. Due to sheer mass, glaciers flow like very
  slow rivers.

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Sheet Glaciers

• More than 90 percent of glacier ice in the world
  is locked up in the gigantic Greenland and
  Antarctic ice sheets.
• Found only in Antarctica and Greenland, ice
  sheets are enormous masses of glacial ice and
  snow expanding over 50,000 square kilometers.

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Sheet Glaciers

• The ice sheet on Antarctica is over 4200 meters
  thick in some areas
• Cover nearly all of the land features except the
  Transantarctic Mountains.

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Sheet Glaciers

• Ice Shelves
• Ice shelves occur when ice sheets extend over the
  sea, floating on the water.
• In thickness they range from a few hundred meters
  to over 1000 meters
• Ice shelves surround nearly all of the Antarctic
  continent

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Sheet Glaciers

• Ice Caps
• Ice caps are miniature ice sheets.
• An ice cap covers less than 50,000 square
  kilometers.
• They form primarily in polar and sub-polar
  regions that are relatively flat and high in
  elevation.

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Ice Ages

• Over the past 2 million years there have been
  many ice ages
• Glaciers spread as far south as St. Louis, New
  York, and Moscow.
• The last ice age ended about 10,000 years ago.

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Mountain Glaciers

• Smaller and much more common
• Found in high mountain valleys all around the
  world
• The largest are found in Arctic Canada, Alaska,
  the Andes in South America, the Himalayas in
  Asia, and on Antarctica.
• More than 1,000 in Western U.S.

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Mountain Glaciers

• Valley Glaciers
• Originate from mountain glaciers or ice fields.
• Spill down valleys, looking much like giant
  tongues.
• Valley glaciers may be very long sometimes
  flowing to sea level

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Mountain Glaciers

• Piedmont Glaciers
• Piedmont glaciers occur when steep valley
  glaciers spill into relatively flat plains, where
  they spread out into bulb-like lobes.
• The Malaspina Glacier in Alaska, covering over
  5,000 square kilometers is one of the most famous
  examples of this type of glacier.

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Mountain Glaciers

• Cirque Glaciers
• Named for the bowl-like hollows they occupy
• They are found high on mountainsides
• Tend to be wide rather than long

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Mountain Glaciers

• Hanging Glaciers
• Also called ice aprons
• Cling to steep mountainsides.
• Like cirque glaciers, they are wider than they
  are long.
• Hanging glaciers are common in the Alps

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Mountain Glaciers

• Tidewater Glaciers
• As the name implies, these are valley glaciers
  that flow far enough to reach out into the sea.
• Responsible for calving numerous small icebergs

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Wind Erosion

• Has its greatest impact where there are fewer
  plants
• Deserts
• Beaches
• Dry bare ground
• Wind erosion works in 2 ways

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Wind Erosion

• Wears down rock
• By blowing sand and other particles against them

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Wind Erosion

• Transports particles from place to place
• Can be short or long distances
• Dust from Sahara can be found across the Atlantic
  in the Caribbean

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The Dust Bowl

• Occurred during the 1930s and lasted nearly a
  decade
• Took place on the U.S. Plains
• Drought and poor farming practices led to major
  dust storms

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The Dust Bowl

• Land produced bountiful crops in previous years

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The Dust Bowl

• But as the droughts of the early 1930s deepened,
  the farmers kept plowing and planting

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The Dust Bowl

• Ground cover that held the soil in place was gone
• Plains winds whipped across the fields raising
  billowing clouds of dust to the skies

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The Dust Bowl

• Even the most well sealed homes could have a
  thick layer of dust on furniture
• In some places the dust would drift like snow,
  covering farmsteads

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The Dust Bowl

• States affected
• Texas
• Oklahoma
• Kansas
• Colorado
• New Mexico.

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As a result of the Dust Bowl..

• Congress passed the Soil Conservation Act of
  1935.
• Educated farmers on soil conservation and
  anti-erosion techniques which included
• Crop rotation
• Strip farming
• Contour plowing
• Terracing and other beneficial farming practices.
• By 1938, the massive conservation effort had
  reduced the amount of blowing soil by 65 percent.