Transcript
Page 1: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation

GLACIERSGLACIERSAND AND

GLACIATIONGLACIATIONII

Page 2: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation

TopicsTopics

Intro Intro Glaciers and the Hydrologic cycleGlaciers and the Hydrologic cycle TypesTypes MovementMovement Glacial landformsGlacial landforms

– Glacial erosionGlacial erosion– Glacial sedimentationGlacial sedimentation– Glacial lakesGlacial lakes

Glaciations and global climateGlaciations and global climate

Page 3: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation

GLACIERGLACIER

A large body of moving ice A large body of moving ice Formed on landFormed on land Recrystallization of snowRecrystallization of snow Types:Types:

– Alpine (valley) glaciersAlpine (valley) glaciers– Continental glaciersContinental glaciers

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Winter Sea Ice- Beaufort SeaWinter Sea Ice- Beaufort Sea

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Sea Ice- Sea Ice- Bering SeaBering Sea

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Timble Glacier, AlaskaTimble Glacier, Alaska

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Page 8: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation

Valley Glaciers in Valley Glaciers in Denali National ParkDenali National Park

Courtesy USGS

Page 9: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation

Hydrologic Cycle - 2% of water is IceHydrologic Cycle - 2% of water is Ice

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What if the glaciers melt?What if the glaciers melt?

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Glaciers-Where they are Glaciers-Where they are

Develop where all of annual snow doesn’t melt Develop where all of annual snow doesn’t melt away in summeraway in summer– Polar regionsPolar regions– Heavy winter snowfallHeavy winter snowfall– High elevationsHigh elevations– 85% in Antarctica85% in Antarctica– 10% in Greenland10% in Greenland

Page 12: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation

Types of GlaciersTypes of Glaciers

Valley glacierValley glacier Continental Glaciers:Continental Glaciers:

– Ice sheets (big)Ice sheets (big)– Ice cap (small)Ice cap (small)

Page 13: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation
Page 14: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation
Page 15: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation
Page 16: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation

Greenland Ice Greenland Ice Sheet:Sheet:

contours indicate contours indicate elevation of ice elevation of ice

sheet above sea levelsheet above sea level

Fig. 12.5

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Ross Ice Shelf, AntarticaRoss Ice Shelf, Antartica

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Page 20: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation

Formation and Growth of Formation and Growth of GlaciersGlaciers

Metamorphism of SnowMetamorphism of Snow Glacial BudgetsGlacial Budgets

– Zone ofZone of accumulation accumulation– Zone ofZone of wastage wastage

» Snow lineSnow line- divides the zones- divides the zones

– Negative budget-Negative budget- Receding glacier Receding glacier– Positive budget- Positive budget- Advancing glacierAdvancing glacier– TerminusTerminus- movement reflects budget- movement reflects budget

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Page 22: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation

GLACIERSGLACIERS

Wastage of glaciers (“shrinkage”)Wastage of glaciers (“shrinkage”)– MeltingMelting

» more melting at lower elevationsmore melting at lower elevations

– EvaporationEvaporation– Calving into IcebergsCalving into Icebergs

» where a glacier flows onto a seawhere a glacier flows onto a sea

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Movement of GlaciersMovement of Glaciers

Valley GlaciersValley Glaciers– Gravity driving forceGravity driving force– Sliding along its base -Sliding along its base -basal slidingbasal sliding– Internal flowage- Internal flowage- plastic flowplastic flow– Rigid zoneRigid zone

» Crevasses may form hereCrevasses may form here

Ice sheetsIce sheets– Move downward & outward from central highMove downward & outward from central high

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Glacial ErosionGlacial Erosion Under glacierUnder glacier

– Abrasion & pluckingAbrasion & plucking

– Bedrock polished & striatedBedrock polished & striated

– Rock flour washes out of glacierRock flour washes out of glacier

– Polishing and roundingPolishing and rounding» ““Sheep Rocks”Sheep Rocks”

– Striations- scratches & grooves on rockStriations- scratches & grooves on rock Above glacierAbove glacier

– Frost wedging takes placeFrost wedging takes place

– Erosion by glaciers steepens slopesErosion by glaciers steepens slopes

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Erosional Landscapes Associated Erosional Landscapes Associated with Alpine Glaciationwith Alpine Glaciation

Glacial valleysGlacial valleys– U-shaped valleysU-shaped valleys– Hanging valleysHanging valleys– Truncated spursTruncated spurs

» Triangular facetsTriangular facets

– Rock -basin lakes (tarns)Rock -basin lakes (tarns)– Rounded knobs- Rounded knobs- rouche moutonneesrouche moutonnees

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Erosional Landscapes Associated Erosional Landscapes Associated with Alpine Glaciationwith Alpine Glaciation

CirqueCirque- at head of valley glacier- at head of valley glacier

– Rock stepsRock steps» Rock basin lakesRock basin lakes

HornHorn Arete- sharp ridgeArete- sharp ridge

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Erosional Landscapes Associated Erosional Landscapes Associated with Continental Glaciationwith Continental Glaciation

Grooved and striated bedrockGrooved and striated bedrock– Grooves may be channelsGrooves may be channels

Rounded hills & mountainsRounded hills & mountains

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Glacial DepositionGlacial Deposition TillTill

– Unsorted debrisUnsorted debris ErraticErratic Moraine- body of tillMoraine- body of till

– Lateral MoraineLateral Moraine– Medial Moraine- where tributaries joinMedial Moraine- where tributaries join– End moraine-End moraine-

» Terminal Terminal

» RecessionalRecessional

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Erratic-Alberta, CanadaErratic-Alberta, Canada

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Other Glacial Landforms Other Glacial Landforms

Drumlins- Drumlins- – Elongated hills of glacial tillElongated hills of glacial till– Point down-glacierPoint down-glacier

EskersEskers– Sinuous ridges of stratified till Sinuous ridges of stratified till – Form in tunnels under the ice sheetForm in tunnels under the ice sheet– Some times 100km long or moreSome times 100km long or more

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Glacial DepositionGlacial Deposition

OutwashOutwash– Stream-deposited sedimentStream-deposited sediment

» sortedsorted

– Braided streams typicalBraided streams typical– EskerEsker– KettleKettle

Glacial lakesGlacial lakes

Page 43: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation
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Glacial LakesGlacial Lakes Pluvial Lakes-Pluvial Lakes-

– Due to wetter climateDue to wetter climate

– Examples: Lake Bonneville, Death ValleyExamples: Lake Bonneville, Death Valley

– Lake Bonneville flood into Snake River CanyonLake Bonneville flood into Snake River Canyon Proglacial LakesProglacial Lakes

– In front of the glacial sheetIn front of the glacial sheet

– Ice dammed lakesIce dammed lakes

– Examples: Great Lakes, Lake MissoulaExamples: Great Lakes, Lake Missoula

Page 46: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation
Page 47: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation

Lake Bonneville- Lake Bonneville- 14,000 yrs ago- 14,000 yrs ago-

UtahUtah

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Lake Bonneville FloodLake Bonneville Flood

The lake was up to 1000 feet deepThe lake was up to 1000 feet deep A ridge on the north side gave wayA ridge on the north side gave way Peak flow 33 million cubic feet/secondPeak flow 33 million cubic feet/second 33 MCF would fill in a tanker train 165 miles long33 MCF would fill in a tanker train 165 miles long A raft would move at 75 mph on a wave 300 ft A raft would move at 75 mph on a wave 300 ft

highhigh Flood left behind giant ripplesFlood left behind giant ripples

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Glacial agesGlacial ages

Northern Europe & North America heavily glaciatedNorthern Europe & North America heavily glaciated– Peak of glaciation 18,000 years agoPeak of glaciation 18,000 years ago– Ended about 10,000Ended about 10,000– We are still in the cold part of the climate cycleWe are still in the cold part of the climate cycle

Episodic climate changesEpisodic climate changes At peak glaciation At peak glaciation

– Average global temperature only 5 degrees colderAverage global temperature only 5 degrees colder

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Effects of Past Glaciation Effects of Past Glaciation

Glacial agesGlacial ages Direct effects in North AmericaDirect effects in North America

– Scoured much of CanadaScoured much of Canada– Cut Great LakesCut Great Lakes– Deposited till & flattened MidwestDeposited till & flattened Midwest– Extensive alpine glaciation in mountainsExtensive alpine glaciation in mountains

Page 54: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation

Effects of Glacial AgesEffects of Glacial Ages

Indirect effectsIndirect effects– Pluvial lakesPluvial lakes– Lowering of sea level Lowering of sea level

» FiordFiord

– Crustal reboundCrustal rebound Evidence for older glaciationEvidence for older glaciation

– TilliteTillite– Late Paleozoic glaciationLate Paleozoic glaciation

» Evidence for a supercontinentEvidence for a supercontinent

– Precambrian glaciationPrecambrian glaciation

Page 55: GLACIERS AND GLACIATION I. Topics n Intro n Glaciers and the Hydrologic cycle n Types n Movement n Glacial landforms –Glacial erosion –Glacial sedimentation

Causes for glaciationCauses for glaciation Astronomical (Milankovitch cycles)Astronomical (Milankovitch cycles)

– Eccentricity of orbit (100,000 yr cycle)Eccentricity of orbit (100,000 yr cycle)– Wobble of rotation axis (41,000 yr cycle)Wobble of rotation axis (41,000 yr cycle)– Precession of equinox (23,000 yr cycle)Precession of equinox (23,000 yr cycle)

Variations in solar radiationVariations in solar radiation Atmospheric changesAtmospheric changes

– CO2 (Greenhouse)CO2 (Greenhouse)– Volcanic ashVolcanic ash

Tectonic causesTectonic causes– Continents near the polesContinents near the poles– Oceanic circulation patternsOceanic circulation patterns


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