Glaciers

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Glaciers
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What is a Glacier

• Glaciers are made up of fallen snow that, over
  many years, compresses into large, thickened ice
  masses.
• Glaciers form when snow remains in one location
  long enough to transform into ice

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Za da Zan glacier
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Birth of a Glacier

• In huge snow fields freshly fallen snow becomes
  compressed and recrystallizes into a rough
  granular ice material Firn
• As the firn thickens it develops solid ice layer
  (due to the compression of the snow on top of
  them)
• This ice then begins to flow downward or outward
  due to the weight difference, this then becomes a
  valley glacier.

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How do they form?
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Could you make a tiny one

• Since glaciers are formed from just snow the
  answer is yes
• Take a handful of snow and or crushed ice and
  squeeze it between your hands

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Different kinds of Glaciers

• Valley Glaciers long, wedge shaped stream of ice
  that occupy mountain valleys
• Continental glacier massive ice sheets that
  move outward in all directions from a common
  center

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Valley Glaciers

• Also known as Alpine Glaciers
• These occur where mountains stretch above the
  snow line. (Everywhere but Australia)

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Continental Glaciers

• Also know as ice sheets
• These are found in Greenland and Antarctica.
• Nunataks inland great mountain peaks where ice
  descends from the peaks
• Ice caps small ice sheets

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The Snow Line

• Snow line the lowest level that permanent snows
  reach in the summer.

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How do they move?

• What makes glaciers unique is their ability to
  move.
• Due to sheer mass, glaciers flow like very slow
  rivers.
• Some glaciers are as small as football fields,
  while others grow to be over a hundred kilometers
  long.

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Movement of St. Franz Josef Glacier

• 1951 1957 1964

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Transport Loose Rock

• Moraines - material carried in the bottom of the
  glacier before it is deposited is called ground
  moraines
• Long lines that build up in the valleys are
  called side (lateral) moraines
• When two glaciers from one they form medial
  (middle) moraines.
• Ice fronts that move large pieces of rock are
  called end moraines.
• Rock flour is a mixture of fine sand and silt
  formed by the crushing of rock under the glacier.

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Glaciers leave their mark

• Striation show the general direction of the
  movement of the glacier scratching the rocks as
  they move over them.
• Cirque a semicircular basin that is formed at
  the head of the glacial valley
• Arete when two cirques are formed next to each
  other the divide between them may becomes narrow.

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Striations
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Cirques
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Arete
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Where are they?

• Presently, glaciers occupy about 10 percent of
  the world's total land area, with most located in
  polar regions like Antarctica and Greenland.
• Glaciers can be thought as remnants from the
  last Ice Age, when ice covered nearly 32 percent
  of the land, and 30 percent of the oceans

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An Ice Age?

• An Ice Age occurs when cool temperature endure
  for extended periods of time, allowing polar ice
  to advance into lower latitudes.
• There has only been 8 ice ages scientist believe
  in the past 750,000 years on Earth.

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Will there be another Ice Age?

• Currently, the Earth is nearing the end of an
  interglacial, meaning that another Ice Age is due
  in a few thousand years.
• This is part of the normal climate variation
  cycle. Greenhouse warming may delay the onset of
  another glacial era, but scientists still have
  many questions to answer about climate change.
• Although glaciers change very slowly over long
  periods, they may provide important global
  climate change signals.

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Antarctica. The Byrd Glacier where it joins the
Ross Ice Shelf.
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Malaspina Glacier, Alaska
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Patagonian Ice Field, Chile and Argentina
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Iceland's largest (8,200 square kilometers) ice
cap, Vatnajökull