chapter 19 glacial modification of terrain. glaciations past and present glaciations past and...

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