Erosion by Glaciers

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Erosion and Deposition by Glaciers Created By
Mr. Kreeger
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Page References and Homework

• Page References
• Page 191-205 Chapter 13
• Homework
• 1-6 on page 195
• 7-12 on page 199
• 13-18 on page 202
• 19-21on page 205

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Table of Contents

1. Glaciers Defined
2. Formation of Glaciers
3. Valley or Alpine Glaciers
4. Continental Glaciers or Ice Sheets
5. Glacier Movement
6. Glacial Deposition
7. Landforms caused by Glacial Deposition
8. Landscape Features

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Roughly 18,000 yrs ago 30 of the earths surface
was covered by glaciers. This period is known as
the GREAT ICE AGE
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Introduction Video Clip
Glaciers
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1. Glaciers Defined

• A large mass of ice, formed on land by the
  compaction and recrystallization of snow, that is
  moving downhill or outward under the force of
  gravity.
• Formed when snowfall gt than rate of melting

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2. Formation of Glaciers

• Form when average incoming snowfallgt than avg.
  amount lost by melting and evaporation? Snow
  increases each year
• Picture A- Formation
• Picture B- Growing
• Picture C- Retreating

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2. Formation of Glaciers cont..

• As snow increases and evaporation occurs ice
  crystals become rounded forming granular snow.
• As more snow falls (alternating melting
  and refreezing compacts snow into a layer called
  firn? grows into solid ice.

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SNOWLINE
6,000m
5,000m
Glaciers Form
4,000m
3,000m
2,000m
Glaciers Do NOT Form
1,000m
Sea Level
North Pole 75N 60N
45N 30N
15N Equator
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3. Valley or Alpine Glacier

• Gravity pulls downward and outward on bottom
  layers
• This type of glacier carves a U shaped valley.
• Remember streams carve a V shaped valley

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U-Shaped Valley
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4. Continental Glacier or Ice Sheets

• These are very old and thick and may cover entire
  land masses, snow is close to sea level
• Moves very slowly because of weight
• When it reaches ocean it can break off? Icebergs
  (called Calving)
• Greenland- 1.7 million square Km (3 Km thick)
• Antarctica- 12.5 million square Km (5 Km thick)

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Depth of Greenland Antarctic Ice Sheets
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Video clip of glacier movement
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5. Glacier Movement

• Stationary Glacier- When rate of movement rate
  of melting
• Winter- Glacier moves more (WHY???)
• Summer Glacier moves less and appears to move
  backwards (WHY???)

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6. Glacial Deposition

• The sediment that is deposited by glaciers is
  unsorted (Called Glacial till)
• Remember that sediment deposited by water is
  sorted.
• If sediment is transported by melt water of
  glacier than it is deposited the same as a river
  would deposit (Sorted)?Outwash

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Glacial till - unsorted
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7. Landforms caused by Glacial Deposition

• Moraines- Unsorted Sediment along the edge of the
  glacier.
• Terminal Moraine-The furthest point of the
  glacier (Long Island)
• Erratic- A large rock that looks misplaced
• Drumlins- Long smooth hills of glacial till,
  points in direction of glacier movement.
• Karnes- melt water from top of glacier
• Kettles- Circular lakes-Ice breaks off and melts
  underground
• Moraine Dammed lake- When a glacial moraine
  blocks a river valley, resulting in a long narrow
  lakes. (Finger lakes)

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Moraine/Terminal Moraine
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Erratic
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Drumlins
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Outwash Plains
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Karnes
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Kettle Lake
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Moraine Dammed Lake
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8. Landscape Features

• Cirques- Semi circular shaped bedrock formed as
  glacier moves back toward mountain.
• Arêtes- Steep sided bedrock formed as glacier
  retreated in opposite direction.
• Horns- Where three arêtes meet up

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Arête
Cirque
U-Shaped Valley
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Kettle Lake
Drumlins
Esker
Outwash plain
Till
Moraine-dammed lake
Glacial Stream
Terminal Moraine