Glaciers

1
Glaciers

• Chapter 15

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Glacial Land Forms Project

• Create a map that identifies different glacial
  land forms found in Southeast Wisconsin.
• Process
• Search using the internet and other sources
  (public library or books or previous knowledge)
  and find as many glacial features in Southeastern
  Wisconsin as you can.
• Create a hand drawn map of Southeastern
  Wisconsin.
• Label all significant cities and roads
• Label all glacial features
• Please use different colors for roads, cities,
  and glacial features
• Specs
• Map Size 8.5 x 11 (normal sheet)
• Due date January 18
• Points possible 20

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15.1 What is a glacier?

• Glacier- a large mass of compacted snow and ice
  that moves under the force of gravity
• Where Glaciers Form
• Areas that are always covered by snow (more snow
  falls than melts)
• Snow line- the lowest elevation at which a
  permanent layer of snow exists
• High latitudes
• High altitudes
• As the latitude gets higher, the altitude of the
  snow line is lower (see chart p. 318)
• How Glaciers Form
• In the valleys of mountains, snow can be 100s of
  meters thick
• The snow near the bottom is compressed to become
  firn
• The firn becomes thicker and harder until it
  eventually becomes ice
• The ice will be pushed down or out by the
  increasing weight of snow on top
• As soon as movement occurs, it is called a glacier

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15.1 What is a Glacier

• Types of Glaciers
• Valley Glaciers
• On mountains with permanent snow
• Snow accumulates in the valleys
• The glacier will travel down the valleys being
  pulled by gravity as snow continues to accumulate
  on top
• A river of ice is the result
• These glaciers exist on all continents except
  Australia
• Can be 2 km long and up to 100 km long
• Southern Alaska and the Himalayas have the
  largest valley glaciers
• Continental Glaciers
• Exist only in polar regions
• Greenland and Antarctica are where snow
  accumulation has been occurring for 1000s of
  years
• Ice is just pushed out from the center of the of
  the continents to the coasts
• The ice can be 3-4 km thick
• The mountains that poke up through this ice are
  called nunataks
• An ice cap is small continental glacier located
  on an island

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15.2 Glacial Movement and Erosion

• How Glaciers move
• Range from a few cm a day to many meters a day
• Factors that affect this include winter
  snowfall, summer melt, and slope.
• The middle of a glacier moves faster than its
  sides due to friction
• Basal slip occurs because of the melt water at
  the base of a glacier, otherwise the cause is
  pure pressure
• Crevasses can open up as the slope changes
• Ice front the point where melting equals forward
  movement
• Icebergs occur when the glaciers ice front is in
  the sea
• This process is called calving
• Some icebergs are the size of small states

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15.2 Glacial Movement and Erosion

• How Glaciers cause erosion
• Glaciers basically pick up and move particles as
  they travel over land
• Particle size can range from dust to huge
  boulders
• Till is the material that a glacier carries
• Moraine is the term when the glacier deposits its
  till
• Moraines can be lateral or medial
• Rock flour is the tiny ground up pieces of rock
  found near the base of the glacier, when rock
  flour mixes with water glacial milk occurs
• Striations- lines scratched in bedrock by till
• The striations will show the direction of the
  glacier
• Plucking-the freeze thaw process at the bottom of
  a glacier will force huge boulders up to be
  carried away by the glacier

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15.2 Glacial Movement and Erosion

• Effects of erosion
• Valley glacier effects-
• Glacial valley- U shaped valley
• Hanging valleys and hanging valleys waterfalls
• Cirque- semicircular basin found at the head of a
  valley glacier
• Cirque lake is what is left after the glacier
  melts away
• Arete- knife lock divide between cirques
• Horn is the top of a mountain surrounded by
  cirques
• Continental glacier effects
• Round and polish everything (the opposite of
  valley glaciers)
• http//www.eoascientific.com/campus/earth/multimed
  ia/glaciers/view_interactive

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15.3 Glacial Deposits

• See pictures on p. 327
• Moraines- large, fairly even deposits of glacial
  till
• End moraine- marks the farthest advance of a
  glacier for a time
• Terminal moraine- marks the overall furthest
  extent of a glacier
• Erratics-large boulders displaced by glaciers
  (holy hill erratic)
• Drumlins- long smooth canoe-shaped hills found in
  groups
• Outwash plains- delta like deposits that follow a
  glacier
• Eskers- snake like ridges that mirror tunnels in
  the glaciers

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15.3 Glacial Deposits

• Kames- small, cone shaped hills of stratified
  sand and gravel (Kewaskum)
• Kettles- bowl shaped hollows found in moraines
  and outwash plains
• Form when buried blocks of ice melt
• Lakes- are caused by moraine dams
• The lakes are often shallow
• They often dont have inlets or outlets so they
  fill with plants and become bogs or swamps
  (Horicon marsh)

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15.4 Ice Ages

• What science says
• The earth has had many ice ages over the last 2
  million years with the last one ending about
  11,000 years ago
• The last ice age stretched from Canada down into
  the Upper Midwest of the US
• Causes of ice ages
• Earths position relative to the sun
• More or less carbon dioxide
• Continental drift
• More atmosphere

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15.4 Ice Ages

• What we can say as Christians
• There could have been an ice age and perhaps
  there was even likely an ice age
• The ice age would have to have been in the last
  10,000 years
• Causes
• Global climate cycles
• Flood water evaporation
• http//www.answersingenesis.org/home/area/faq/icea
  ge.asp