REVIEW: Glacier classification

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REVIEW Glacier classification
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Major types of glaciers (morphological
classification)

• Cirque glaciers
• Mountain glaciers
• Form in amphitheater-shaped depressions (called
  cirques!)
• Size-few kilometers
• Valley glaciers
• Streams of ice that flow downvalley from a cirque
• 100s of km
• Piedmont glaciers
• Glaciers that discharge ice from mountains onto
  broad lowlands
• Ice becomes unconfined
• Ice sheets
• Bread ice masses not confined to valleys, massive
  thicknesses of ice
• 1000s of km
• Creates its own topography, creates isostatic
  depression

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Types of Glaciers Cirques
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Cirque glacier
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Little Ice age cirque of the Teton Glacier
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Valley glaciers
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valley glacier
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Valley glacier
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Valley glacier complex Denali NP
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Valley glaciers
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Ice sheet
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Types of glaciers ice sheets
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Ice caps on Iceland
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Wet based (temparate) vs. cold based (polar)
glaciers

• Wet-based or temperate glaciers
• Glaciers at pressure melting point that slide on
  a layer of liquid water (large component of basal
  sliding)
• Lots of meltwater, higher velocities, more
  erosion
• Cold-based or polar glaciers
• Glaciers are stuck to their bed. These glaciers
  are characteristic of cold, polar areas.
• No meltwater, minimal slippage along base, lower
  velocity, less erosion, less geomorphic work

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Glacial features cravasses
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Calving Glaciers in Alaska
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The Earths Climate Past, Present and Future

• Fall 2006
• 440-555PM   TuTh
• GEOL 297/ GEOL 397/GEOG 397

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Weird words in geomorphology!

• arete fishbone
• Roches moutonees rock sheep
• DrumlinGaelic druim the crest of a hill
• Paternoster our father in Latin. Lakes are
  thought to resemble a rosary with alternating
  beads and string (streams) inbetween them.

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Glacial landforms erosion and deposition

• Glaciers ERODE landscapes by scraping underlying
  bedrock, pushing debris along the sides and front
  of a glacier, and carrying material on and within
  the glacier

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Glacial landforms erosion and deposition

• Glaciers DEPOSIT material that has been eroded on
  the ground (till) along margins (moraines) and as
  material reworked by streams (outwash)

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Class presentations striations and chattermarks
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Glacial erosional features

• Striations
• Scratches on rocks from debris at base of glaciers

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Glacial ErosionAbrasion

• Grinding by transported grains of silt and
  larger sizes.
• Effects polish, striations, grooves.
• Embedded fragments shared these features as
  well as facets.

Longitudinal glacier flow
Debris particle paths
Diverging ice flow
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Glacial ErosionAbrasion

• Evidence
• Polish, striations, grooves, facets (on clasts)
• Done by different sizes of embedded debris
• Rock flour
• Seen as cloudiness or milkiness in glacial
  meltwater.
• Direct measurement
• Rates of a few mm/yr
• SLIDES

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Glacial ErosionAbrasion

• Influencing Factors
• Adequate amount of basal debris
• Replenishment of basal debris
• High rate of basal sliding
• Adequate thickness to apply pressure
• Hardness of embedded debris
• Angularity and size of embedded fragments

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Glacial ErosionAbrasion

• Replenishment of Debris

Longitudinal glacier flow
Movement towards glacier bed equal to amount
of basal melting
Path taken by particle
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Glacial ErosionPlucking

• Fractures
• Created by theglacier by draggingembedded
  fragmentschattermarks

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Class presentations crevasses and bergschrunds
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Glacial Cravasses

• Cravasses are cracks in the glacial ice
• perpendicular to direction of ice movement
• Often represent areas of extension in ice

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Class presentations U-shaped valleys and
hanging valleys
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Glacial erosional features

• Glacial valleys
• Steep U-shaped valleys eroded by glaciers

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Glacial ErosionFeatures of Alpine Areas

• Glacial Troughs
• Transverse profiles are said to be U-shaped but
  vary in actual shape.

V-shaped
ParabolaW/2Dlt1
Semi-circleW/2D1
W/2Dgt1
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Glacial ErosionFeatures of Alpine Areas

• Features Associated with Troughs
• Truncated spurs
• Result of straightening valley.
• Hanging valleys
• Greater erosion in main valley leaves
  discordant relationship.
• Commonly marked with waterfall.

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Valley glaciers and fjords
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Class presentations cirques and tarns
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Glacial ErosionAlpine Feature - Cirque

• Half-bowl shaped scoup just below highest
  mountains.

Headwall
Snowline
Threshold
Basin
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Glacial ErosionAlpine Areas - Cirques

• Probably originate as nivation hollows.

Protalus Rampart
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Glacial ErosionAlpine Areas - Cirques

• Expand into cirque as glacier forms and advances.

Bergsrund
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Glacial ErosionAlpine Areas - Cirques

• Cirque Aspect
• NE aspect in Northern Hemisphere favors
• 1) Protection from sun
• 2) Receives wind-driven snow

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Class presentations horns and arrets
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Glacial ErosionAlpine Features

• Aretes sharp-crested ridge dividing two
  glaciated areas
• Cols low areas through ridges such as
  aretes often passes
• Horns joining of 3 cirques

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Class presentations moraines (lateral,
terminal, medial)
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Glacial deposits

• Glacial moraines
• Ridges of sediment deposited on sides (lateral
  moraines) and ends (terminal moraines) of
  glaciers
• Moraines form by glacier dumping material at the
  same location over time (conveyor belt), and
  pushing material in front of moving ice
  (bulldozer)
• Glacial deposits mark where a glacier has been in
  the same place for a period of time.

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How can you recognize a moraine in the field or
on a map?

• Topographic clues moraines are elongated ridges
• Moraines may dam lakes (valley glaciers)
• Depositional clues moraine deposits are
  composed of till
• Morphologic clues the slope of the moraine is
  initially steep and becomes more subdued
  (rounded) over time

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Class presentations rouche moutonees and
whalebacks
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Glacial ErosionPlucking (Quarrying)

• Pulling out large blocks of rock along fractures.
• May be dragged free or refrozen to base of
  glacier (regelation).

GLACIER Flow
Preassure-induced Melting
Refreezing
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Glacial ErosionFeatures Produced by Ice Sheets

• Whalebacks streamlined, abraded hills oriented
  parallel to ice flow. Dimensions height 1 to
  10 m length 1 m to several km. Surfaces often
  striated.

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Glacial ErosionFeatures Produced by Ice Sheets

• Formation of Whalebacks

Fast erosion
Flowing ice
Little erosion beneath stagnant or slowly moving
ice
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Glacial ErosionFeatures Produced by Ice Sheets

• Roches moutonees are streamlined bedrock hills
  with the steep end downglacier.
• Polish and striations on upglacier side indicate
  abrasion there.
• Downglacier side eroded by plucking is steep and
  irregular.
• Dimensions are similar to those for whalebacks
  and rock drumlins.

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Glacial ErosionFeatures Produced by Ice Sheets

• Characteristics of Roche Moutonees

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Class presentations paternosters lakes, glacial
longitudinal profiles (see figure 10.12)
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Glacial ErosionFeatures of Alpine Areas

• Glacial Steps

Riegels
Riegels
Basins
Riegels
Basins
Basins
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Glacial ErosionFeatures of Alpine Areas

• The largest and otherwise most significant
  glacial landform of alpine areas is the glacial
  trough.
• Longitudinal profiles of glacial troughs are
  steep in their upper parts and are also stepped
  and are commonly stepped.
• Paternoster lakes may occupy the floors of the
  steps.

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Class presentations till (non-stratified)
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Till

• Till is a name for material transported and
  deposited by a glacier
• Moraines are made up of till
• Lodgement till (till at bottom of glacier)

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Class presentations stratified drift
(fluvioglacial)
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Class presentations sandurs and outwash plains
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Glacial outwash (Knik glacier, AK)
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Class presentations kame and kame terraces
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Class presentations kettles and eskers
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Glacial depositional features
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Class presentations drumlins and fluted surfaces
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Glacial ErosionFeatures Produced by Ice Sheets

• Rock drumlins have the profile of true drumlins
  (steeper end upglacier) but are composed of
  bedrock. Dimensions height up to 50 m length
  up to several km

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Glacial ErosionFeatures Produced by Ice Sheets

• Rock drumlins
• 1. May occur in drumlin fields with true
  drumlins.
• 2. May have survived because they are composed
  of more resistant rocks.
• 3. May have been preglacial hills overridden and
  smoothed by glacier.

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Geomorphic Mystery!
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Glacial Erratics

• a glacial erratic is a boulder carried by glacial
  ice and deposited some distance from its place of
  origin.

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Wallowa Lake, Oregon

• 4. What are the features shown by the arrows?
  How were they formed?

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Tan McArthur Rim, Oregon
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Yosemite Striations

• 3. What are the possible directions of glacial
  movement? Use compass directions below

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Glaciers in the Tetons
Can you identify moraines on this photo? What
kind of glacier formed these moraines? (valley
glacier, ice sheet, cirque glacier, piedmont
glacier. . )
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Glaciers in the Tetons

• Ice cap over Yellowstone
• Valley glaciers in Tetons

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Periglacial processes and landforms

• Periglacial processes and landforms
  characteristic of cold areas

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Permafrost

• Permanently Frozen Ground (or at least frozen
  more than one year). Mean annual ground
  temperature is less than 0 Celsius.
• Can be up to 1500 meters deep.
• Active layer top layer 1 to 3 meters thick.
  This active layer thaws during the summer.
• Geomorphic significance of permafrost
• confines water and frost to the active layer
  between the permafrost table and the ground
  surface
• descent of the freezing plane from the surface
  pressurizes the soil water, reducing the freezing
  temperature and maintaining the thawed (active)
  during fall freeze up
• the growth and decay of segregated ground ice
  causes heave and subsidence

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Permafrost
Source Natural Resources Canada - Terrain
Sciences Division - National Permafrost Database).
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Permafrost
Source Natural Resources Canada - Terrain
Sciences Division - National Permafrost Database).
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Frost wedging
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Frost wedging
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Gelilfluction
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Gelilfluction
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Patterned ground
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Rock Glaciers!