chapter 19 glacial modification of terrain. glaciations past and present glaciations past and...
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Chapter 19Chapter 19
Glacial Modification of TerrainGlacial Modification of Terrain
Glacial Modification of TerrainGlacial Modification of Terrain
Glaciations Past and PresentGlaciations Past and Present Types of Glaciers Types of Glaciers How Glaciers FormHow Glaciers Form Continental Ice SheetsContinental Ice Sheets Mountain GlaciersMountain Glaciers The Periglacial EnvironmentThe Periglacial Environment
Pleistocene GlaciationPleistocene GlaciationAt maximum covered 1/3 of total land surface
The Laurentide ice was the most extensive Pleistocene ice mass
Extent of Glacial Ice Today Extent of Glacial Ice Today 10% of land surface
Indirect Effects of Pleistocene Indirect Effects of Pleistocene GlaciationGlaciation
Erosion & deopostion from meltwaterErosion & deopostion from meltwater Sea-level change: cooling lowered – Sea-level change: cooling lowered –
warming raised warming raised Isostacy or rebound i.e. crustal Isostacy or rebound i.e. crustal
depressiondepression Increased rain developments: more Increased rain developments: more
moisture available – more lakesmoisture available – more lakes
Types of GlaciersTypes of Glaciers Continental Ice Continental Ice
SheetsSheets Mountain GlaciersMountain Glaciers
Highland IcefieldsHighland Icefields Alpine GlaciersAlpine Glaciers ConfinedConfined
UnconfinedUnconfined
Continental Ice Sheet - Continental Ice Sheet - GreenlandGreenland
Completely inundate Completely inundate all terrainall terrain
Spread outward in all Spread outward in all directionsdirections
Because of size, may Because of size, may influence climateinfluence climate
Unconfined
Outlet GlacierOutlet Glacier
Along margin of sheetAlong margin of sheet Between hills or Between hills or
mountains to the seamountains to the sea
Continental
Antarctica – Sheet vs. ShelfAntarctica – Sheet vs. ShelfContinental - Unconfined
Larsen Ice Shelf - CalvingLarsen Ice Shelf - Calving
Mountain - Highland Mountain - Highland IcefieldsIcefields
Confined GlaciersConfined Glaciers
Cirque
Valley
Piedmont
Alpine GlaciersAlpine Glaciers
Cirque
Valley
How Glaciers FormHow Glaciers Form
Changing Snow to IceChanging Snow to Ice Glacial MovementGlacial Movement Erosion by GlaciersErosion by Glaciers Transportation by GlaciersTransportation by Glaciers DepositionDeposition
GlaciersGlaciers MeltwaterMeltwater
How Glaciers FormHow Glaciers Form
In combination, these factors influence In combination, these factors influence the amount and distribution of solar the amount and distribution of solar radiation reaching the Earth. radiation reaching the Earth.
Changes vary with both latitude and Changes vary with both latitude and season.season.
Changes in the amount of solar radiation Changes in the amount of solar radiation drive the growth and melting of major ice drive the growth and melting of major ice sheets. sheets.
Three parameters important to ice sheet Three parameters important to ice sheet waxing and waning:waxing and waning:
1.1. Changes in the eccentricity of the Earth's Changes in the eccentricity of the Earth's orbit orbit
2.2. Changes in the tilt of the Earth's axis Changes in the tilt of the Earth's axis 3.3. The precession of the equinoxesThe precession of the equinoxes
Snow to IceSnow to Ice Snow crystallizes directly from water vaporSnow crystallizes directly from water vapor It is NOT frozen waterIt is NOT frozen water
It is 1/10 as It is 1/10 as dense as waterdense as water
Compressed to Compressed to granular form 1/5granular form 1/5
Then to ½ densityThen to ½ density Called Neve or Called Neve or
FirnFirn With time, to 9/10With time, to 9/10 Blue glacial iceBlue glacial ice
Accumulation and AblationAccumulation and Ablation
Figure 19-9
Glacial Glacial MovementMovement
Glacial ice deforms Glacial ice deforms rather than breaksrather than breaks
Partial melting allows it Partial melting allows it to slideto slide
Glacial TillGlacial Till
Glacial ErraticGlacial Erratic
Continental Ice SheetsContinental Ice Sheets
Development and FlowDevelopment and Flow Erosion by Ice SheetsErosion by Ice Sheets Deposition by Ice SheetsDeposition by Ice Sheets
Kames and KettlesKames and Kettles MorainesMoraines DrumlinsDrumlins
Glaciofluvial featuresGlaciofluvial features Outwash Plains, Eskers, and KamesOutwash Plains, Eskers, and Kames
Ice Sheet DepositionIce Sheet Deposition
Kames and KettlesKames and Kettles
Kettle Formation
Kame
Growth of a Terminal Growth of a Terminal MoraineMoraine
Mountain GlaciersMountain Glaciers Development and FlowDevelopment and Flow Erosion by Mountain GlaciersErosion by Mountain Glaciers
Mountain LandformsMountain Landforms Cirques, Arretes, HornsCirques, Arretes, Horns TarnsTarns
Valley LandformsValley Landforms Glacial TroughGlacial Trough Paternoster LakesPaternoster Lakes Hanging ValleysHanging Valleys
Deposition by Mountain GlaciersDeposition by Mountain Glaciers
Mt. Rainier, WAMt. Rainier, WA
CirquesCirques
Figures 19-26 and 19-27
Mountain Landform Mountain Landform DevelopmentDevelopment
Figure 19-28
Glacial TroughGlacial Trough
Glaciated ValleysGlaciated Valleys
Medial MorainesMedial Moraines
Figure 19-38
Moraines in MountainsMoraines in Mountains
Outwash DepositionOutwash Deposition Ice prevented outwash deposition in Ice prevented outwash deposition in
Wellfleet HarborWellfleet Harbor
Cape Cod GlaciationCape Cod Glaciation
Outwash Plain GreenlandOutwash Plain GreenlandGlacial Boulder Eastham, MAGlacial Boulder Eastham, MA
Glacial Erosion Cape CodGlacial Erosion Cape Cod
•6,000 years ago
•Before wave erosion
present pattern of erosion
•Present pattern of
erosion
Cape Cod GeologyCape Cod Geology
Aerial Greenland Ice CapAerial Greenland Ice Cap