glaciers and glaciation ii. topics n glacial landforms –glacial sedimentation –permafrost...

GLACIERSGLACIERSAND AND

GLACIATIONGLACIATIONIIII

TopicsTopics

Glacial landformsGlacial landforms– Glacial sedimentationGlacial sedimentation– PermafrostPermafrost– Glacial lakesGlacial lakes

Glaciations and global climateGlaciations and global climate

Terminal moraineTerminal moraine

Courtesy Gerald Osborn

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

Drumlin field in WisconsinDrumlin field in Wisconsin

PermafrostPermafrost

Frozen groundFrozen ground Found in Arctic Found in Arctic

– North America North America – RussiaRussia

Formed during last ice ageFormed during last ice age More than 1000 m deep in placesMore than 1000 m deep in places Global warming -> melting of permafrostGlobal warming -> melting of permafrost

Distribution Distribution of permafrost of permafrost

in the in the northern northern

hemispherehemisphere

Fig. 12.29

Lateral variations in Lateral variations in permafrost in Siberiapermafrost in Siberia

Fig. 12.30

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

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

UtahUtah

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 a tanker train 165 miles long33 MCF would fill 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

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

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– Allowed Natives to walk from SiberiaAllowed Natives to walk from Siberia

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

Causes for glaciationCauses for glaciation

AstronomicalAstronomical Variations in solar radiationVariations in solar radiation Atmospheric changesAtmospheric changes Tectonic causesTectonic causes

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 Wobble of rotation axis (41,000 yr cycle)cycle)

– Precession of equinox (23,000 yr cycle)Precession of equinox (23,000 yr cycle) Variations in solar radiationVariations in solar radiation

Variations of Earth’s orbit

Tilt of Earth’s Rotation Axis

Wobble of the rotation axis: Precession

Fig. B12.5

Causes for glaciationCauses for glaciation

Atmospheric changesAtmospheric changes

– COCO22 (Greenhouse effect) (Greenhouse effect)

– Volcanic ashVolcanic ash Tectonic causesTectonic causes

– Continents near the polesContinents near the poles– Oceanic circulation patternsOceanic circulation patterns

Gas Concentrations in Deep ice Gas Concentrations in Deep ice core-Antarticacore-Antartica

Fig. 12.34

Causes for glaciationCauses for glaciation

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

Paleozoic (300 Ma) GlaciationPaleozoic (300 Ma) Glaciation

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

Retreating Rhone GlacierRetreating Rhone Glacier

S. C. Porter