Glaciers
What is a glacier?
 A glacier is a moving river of ice that forms from the
accumulation and compaction of snow.
 Glaciers flow down slope or outward due to gravity and the
pressure of their own weight.
Glacier Formation & Growth
 Glaciers form when snow falls, melts slightly then refreezes.
(up to 90% of new snow is spaces between the crystals)
 Snow melts from warm air (sublimation) or from pressure
(pressure melting).
 It then becomes firn, (German for “last year”)if it survives the
summer melting season.
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Where are they found?
 Glacier growth and formation depends on latitude (North &
South) and altitude (how high up).
 As latitude ↑ the altitude ↓. (Latitude at the equator is 0°)
 Glaciers form and grow where snow accumulation exceeds
losses by summer melting.
 Minnesota gets to warm in the summer to have glaciers.
Alpine Glaciers in temperate zones only exist at higher
elevations
Grand Tetons
Types of glaciers
 Alpine\Valley - high in the mountains
 Continental - an ice mass that is so large that it covers much
or all of a continent.
Alpine glaciers
Cirque- a semicircular basin found at the head of a glacier
valley.
Alpine Glaciers
 Valley/ Piedmont- “foot of the mountain” Flow in an existing
river valley, unconfined at the bottom. If bottom is in water, it
is called a Tidewater.
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is called a Tidewater.
Alpine Glaciers
 Ice caps- form at the tops of mountains
Continental Glacier
Glacial budget
  What is a budget?
 The difference between the annual gain, or accumulation of
snow and ice and its annual loss, or ablation, by melting and
sublimation.
 If more gain than ablation= glacier grows or “advances”
 If less gain than ablation= glacier shrinks or “retreats”
Glacier anatomy
 Zone of accumulation- Top
 Zone of ablation- Bottom
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Glacial Erosion
 Abrasion- Rocks frozen in the ice scrape along the bedrock
(like rubbing sandpaper on wood or your knees on the
sidewalk) This produces striations- or scratches in the bedrock.
 Plucking or quarrying- when the glacier lifts chunks of bedrock
from the bedrock below.
Effects of glacial erosion
Before…
Glacial erosion
During…
Glacial erosion
After…
Alpine- glacial erosional features
Small Scale
 Striations and Grooves
Larger Scale
 Roche Moutonnée
 Cirques (1 glacier)Tarn
Arêtes (2 glaciers)
Horns (3+ glaciers)
 U-Shaped valleys
 Fjords
 Hanging Valley
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 Fjords
 Hanging Valley
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Alpine- glacial depositional features
Landforms
 Moraines (by ice)
 Lateral
 Medial
 Terminal or End
 Recessional
Sediments
 Till (by ice)
 Outwash (by meltwater)
Continental- glacial erosional features
Small Scale
 Striations and Grooves
Larger Scale
 Roche Moutonnée
 Whaleback Forms
 Deep Lakes (e.g. Great Lakes, Finger Lakes)
Continental- glacial depositional features
Landforms
 Drumlins
 Moraines (by ice)
 Terminal
 Recessional
 Eskers (by meltwater)
 Outwash Plains (by meltwater)
 Kettle
 Kame
Sediments
 Tills (by ice)
 Outwash (by meltwater)
 Loess (from winds)
Arête
Areté:
Glacier National Park-Going to the Sun Road “Bishop’s
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Glacier National Park-Going to the Sun Road “Bishop’s
Cap”
Formed as separate glaciers erode opposite sides of a ridge
Areté: “knife edge”
Glacier National Park. Hike up Cirque: slide 5
Formed as separate glaciers erode opposite sides of a ridge
Cirque
Cirque: birth place of Alpine Glaciers: Deep bowl shaped
depression carved out as ice collected and carved
downward.
Glacier in Cirque:
Above Leigh Lake Grand Teton National Park
Deep lakesHow the Great Lakes were formed
Drumlin
 Are long canoe-shaped hills that are usually found in groups
(swarms).
 Most likely former moraines reformed as ice advanced again.
Drumlins
 Show direction of ice advance:
 Steeper in the direction the ice came from
 Longer in the “down-ice” direction
Drumlin
Erratics- Large boulders that have been transported into an
area by a glacier.
-Different than surrounding rock types
-Signs of weathering (sub angular rounding)
Erratics-Different than surrounding rock types
-Signs of weathering (sub angular rounding)
Esker
 Rivers of meltwater flow under and inside the ice sheet.
 These rivers carry and deposit sediment along the channel
bed.
 Long winding ridges left behind
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 Long winding ridges left behind
Eskers- (this tunnel is 20 ft. tall) Sediment will fill up in the
tunnel
Eskers: stratified sediment
(roadcut)
Fjord
-Flooded glacially eroded valley.
-Any place alpine glaciers meet the sea
Alaska, Norway, Newfoundland
Hanging Valley- Glacier National Park-Going to the Sun
Road
Formed as a tributary glacier flows into a deeper glacier.
Hanging Valley & Waterfall
Glacier National Park-Going to the Sun Road
Formed as a tributary glacier flowed into a deeper glacier.
Horn
 Formed as 3 or more separate glaciers erode opposite sides
of a mountain peak.
Horn:
Glacier National Park-Going to the Sun Road
Kame
 -Also formed as sediment accumulates in holes in the ice
sheet
Kame
- Small cone-shaped hills that are made of sand and gravel.
- Deposited at the end of rivers flowing under an ice sheet.
Like a stranded delta or alluvial fan
Kettle (lake)
 Holes left in outwash plain from stranded pieces of glacial ice.
They often times fill up with water to become lakes. (ie.
Minnesota land of 10, 000 lakes)
Kettle Lakes- Central MN
Loess
Moraine dammed lake
Moraines
 The accumulation of glacial till, looks like a upside down “U”
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 The accumulation of glacial till, looks like a upside down “U”
shaped hill.
Lateral (side) MorainesAlpine only- confined and scrape off the sides of valley &
stuff falls off the sides onto glacier
Recessional Moraines
•  Created as glacier retreats.
•  New moraines formed whenever glacial toe over the same
area for some time
Medial (middle) Moraines
 Combination of two lateral moraines after they merge into a
larger ice stream.
Terminal Moraines
•  Form at the end of the glacier (toe, snout or terminus)
•  Terminal marks the FARTHEST the glacier advanced
Outwash Plain
 Material deposited by glacial meltwater. It is sorted and
layered.
 Finer sediment is deposited further away from the ice margin.
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 Outwash near toe of Alpine Glacier:
Seward, AK
Roche Moutonnêe A roche moutonnee is a rock hill shaped by glaciers. It has a
smooth up-ice side (stoss) and a rough, plucked and cliff-girt
surface on the down-ice side (lee). The upstream surface is
often marked with striations.
Striations/Grooves
small & large scratches in bedrock (abrasion) caused by
sediment embedded in glacial ice
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Tarn- cirque lake
Mt. Whitney, CA
Till
Till
 The material that is deposited directly by glacial ice. Often
rich soil is left behind, which is good for farming.
U-Shaped Valley
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rich soil is left behind, which is good for farming.
U-Shaped Valley
Grand Teton National Park --Leigh Lake
Continental vs. Alpine Glacier
 Continental
 Larger
 Moves like spreading pancake batter
 Radiate from central domes
 Erosion: smoothes land surface--rounds mountain tops
 Depositional features dominate landscape
  Alpine
◊ Smaller--fills mountain valleys
◊ Moves like a slow river
◊ Erosional features dominate landscape:
◊ widens valleys
◊ Sharpens peaks
◊ Deposition: similar features as Continental, but smaller
Calving
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Ice Age- Not the movie
 A long period of climatic cooling during which the continents
are glaciated repeatedly. Also called a glacial period
 Interglacial period=time of warming between glacial periods.
This is where we are right now.
Past Continental Ice Sheets
Ice Advances of the Pleistocene(2 million to 10,000 years
ago)
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Glaciers in N. America
 Ice was several kilometers thick.
 Because water was locked up in ice, water level was about
140 meters lower than today.
 Canada, Alaska and high regions were buried under ice.
Modern Ice Sheets
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 Much of Greenland has been pushed below sea level.
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 Much of Greenland has been pushed below sea level.
Glaciers as tools to determine past climate
 Certain organisms that live in the water, foraminfera, create
shells. The temperature of the water determines which way the
shell curves. Colder than 8°C= left, warmer than that = to the
right.
Glacier Review
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