Glaciers and Glaciers and Periglacial Periglacial LandformsLandformsProcesses and Processes and

LandformsLandforms

PaleoclimatologyPaleoclimatology

OverviewOverview

GlaciersGlaciers Glacial ProcessesGlacial Processes Glacial Glacial

Landforms Landforms Periglacial Periglacial LandscapesLandscapes

The PleistoceneThe Pleistocene PaleoclimatologyPaleoclimatology

ObjectivesObjectives Describe the different forms of glaciers in terms of Describe the different forms of glaciers in terms of

the similarity of their formation and differences in the similarity of their formation and differences in spatial extentspatial extent

Explain the interrelationships between the Explain the interrelationships between the processes of glacier formation, and those of processes of glacier formation, and those of glacial motionglacial motion

Relate glacial motion to the geomorphological Relate glacial motion to the geomorphological themes of erosion, transportation and deposition, themes of erosion, transportation and deposition, and describe the landforms associated with eachand describe the landforms associated with each

Identify various glacial landforms and describe Identify various glacial landforms and describe the processes that created themthe processes that created them

Describe the features and processes of periglacial Describe the features and processes of periglacial landscapeslandscapes

Describe some of the significant features of the Describe some of the significant features of the PleistocenePleistocene

Identify major sources of climatic variability and Identify major sources of climatic variability and explain how they contribute to climate changeexplain how they contribute to climate change

GlaciersGlaciers Definition: A large mass of ice, flowing across Definition: A large mass of ice, flowing across

the land under the influence of gravity and their the land under the influence of gravity and their own weightown weight

TypesTypes Alpine glaciers: Mountain glaciers, follow drainage Alpine glaciers: Mountain glaciers, follow drainage

patternspatterns Snowfield: area above snowline which provides ice for Snowfield: area above snowline which provides ice for

glaciersglaciers Cirque glaciers: glaciers originating in basins of Cirque glaciers: glaciers originating in basins of

accumulated snow accumulated snow Valley glaciers: several cirque glaciers merge into a greater Valley glaciers: several cirque glaciers merge into a greater

downstream flowdownstream flow Piedmont glaciers: after leaving the mountain slopes, Piedmont glaciers: after leaving the mountain slopes,

several valley glaciers can merge into a larger flow across several valley glaciers can merge into a larger flow across the landscapethe landscape

Tidal glaciers: occur if a glacier reaches the sea. Large Tidal glaciers: occur if a glacier reaches the sea. Large pieces of ice can break off forming ice bergspieces of ice can break off forming ice bergs

Continental glaciers: continuous Continental glaciers: continuous expanses of solid ice that subsume expanses of solid ice that subsume broad landscapes, including drainage broad landscapes, including drainage systems and surrounding peakssystems and surrounding peaks

Ice sheetsIce sheets cover entire continental massescover entire continental masses

Antarctica (90% coverage)Antarctica (90% coverage) Greenland (81% coverage)Greenland (81% coverage)

ice mass can achieve depths of 2000 – 3000 ice mass can achieve depths of 2000 – 3000 metersmeters

actual landmasses can be isostatically actual landmasses can be isostatically depressed below sea leveldepressed below sea level

Ice capsIce caps covers an area less than 50,000 sq. km. and covers an area less than 50,000 sq. km. and

typically has a circular shapetypically has a circular shape Ice fieldsIce fields

Ice fills elongated valleys along mountain Ice fills elongated valleys along mountain rangesranges

Glacial ProcessesGlacial Processes

FormationFormation Zone of Accumulation: area above Zone of Accumulation: area above

snowline where snow exists year-roundsnowline where snow exists year-round Snow accumulates in basins and becomes Snow accumulates in basins and becomes

compacted under its own weightcompacted under its own weight Snow becomes firn (compacted, granular Snow becomes firn (compacted, granular

snow)snow) Firn becomes glacial ice (exhibits strata from Firn becomes glacial ice (exhibits strata from

accumulation)accumulation)

Mass BalanceMass Balance Above the snow line, in the Zone of Accumulation, mass Above the snow line, in the Zone of Accumulation, mass

is added to the glacieris added to the glacier Below the snow line, the glacial ice can melt, sublimate, Below the snow line, the glacial ice can melt, sublimate,

deflate in the wind, or break off the main glacierdeflate in the wind, or break off the main glacier Ablation or Waste are terms used to describe these lossesAblation or Waste are terms used to describe these losses Zone of Ablation: the area below snowline where mass is lost Zone of Ablation: the area below snowline where mass is lost

from the glacierfrom the glacier Mass balance refers to the rate of accumulation Mass balance refers to the rate of accumulation

compared to the rate of ablationcompared to the rate of ablation Positive balance: accumulation greater than ablation; glacier Positive balance: accumulation greater than ablation; glacier

advancesadvances Negative balance: ablation exceeds accumulation; glacier Negative balance: ablation exceeds accumulation; glacier

retreatsretreats With current climate change, the world’s glaciers are largely in With current climate change, the world’s glaciers are largely in

retreatretreat When rates of accumulation and ablation are equal, glacial When rates of accumulation and ablation are equal, glacial

movement continues to occur, but there is no net advance or movement continues to occur, but there is no net advance or retreatretreat

Glacial MovementGlacial Movement Simultaneous sliding and oozing motionSimultaneous sliding and oozing motion Frictional movementFrictional movement

glacial ice rubs against bedrock on the sides and glacial ice rubs against bedrock on the sides and bottom of the valleybottom of the valley

Abrasion and Plucking (erosional process)Abrasion and Plucking (erosional process) Lateral and medial moraines (transportation Lateral and medial moraines (transportation

features)features) Plastic movementPlastic movement

glacier moves faster internally than along frictional glacier moves faster internally than along frictional edgesedges

Causes cracks (crevasses) to form on the surfaceCauses cracks (crevasses) to form on the surface SurgesSurges

Glaciers have been known to move several meters Glaciers have been known to move several meters in one dayin one day

requires either large accumulations of mass, or requires either large accumulations of mass, or lubricating meltwaters along the sides and bottomslubricating meltwaters along the sides and bottoms

Glacial LandformsGlacial Landforms ErosionErosion

PluckingPlucking AbrasionAbrasion

TransportationTransportation Surface loadSurface load Suspended load (englacial transport)Suspended load (englacial transport) Along marginsAlong margins

DepositionDeposition Occurs as a result of ablationOccurs as a result of ablation Melting and outwash sort transported Melting and outwash sort transported

material by mass and texturematerial by mass and texture Larger objects deposited in situLarger objects deposited in situ Smaller sediments carried out by outwashSmaller sediments carried out by outwash

Erosional Features of Alpine Erosional Features of Alpine GlaciersGlaciers Modified upslope drainageModified upslope drainage

U-shaped valleysU-shaped valleys HornsHorns ArArêêtestes CirquesCirques Hanging valleysHanging valleys Tarns and paternoster lakesTarns and paternoster lakes FjordsFjords

Depositional Features of Alpine GlaciersDepositional Features of Alpine Glaciers Glacial DriftGlacial Drift

Deposits of transported material (cobbles and Deposits of transported material (cobbles and finer sediment)finer sediment)

Stratified drift: deposited by melt waters, sorted by Stratified drift: deposited by melt waters, sorted by sizesize

Glacial till: unsorted material deposited in place by iceGlacial till: unsorted material deposited in place by ice MorainesMoraines

Deposition of glacial till by retreating glaciersDeposition of glacial till by retreating glaciers Rapid ablation causes till to be dispersed over a Rapid ablation causes till to be dispersed over a

surface, creating a surface, creating a ground moraineground moraine or or till plaintill plain Slowing retreats (punctuated by periods of Slowing retreats (punctuated by periods of

equilibrium) concentrate deposits of tillequilibrium) concentrate deposits of till terminal moraines mark the farthest extent of glacial terminal moraines mark the farthest extent of glacial

advanceadvance recessional moraines mark periods of slowing retreat recessional moraines mark periods of slowing retreat

during periods of general retreatduring periods of general retreat

Features of Continental GlaciationFeatures of Continental Glaciation Erosional featuresErosional features

deranged drainagederanged drainage roche moutonnroche moutonnééee

Depositional featuresDepositional features Terminal and recessional morainesTerminal and recessional moraines Till plain, outwash plainTill plain, outwash plain EskersEskers KettlesKettles KamesKames DrumlinsDrumlins

Periglacial LandscapesPeriglacial Landscapes Features of Subarctic and Polar (tundra) Features of Subarctic and Polar (tundra)

climates that are not directly related to climates that are not directly related to glaciationglaciation

ProcessesProcesses Physical weatheringPhysical weathering Mass movementMass movement ClimateClimate SoilSoil

FeaturesFeatures PermafrostPermafrost frost actionfrost action ground iceground ice

PermafrostPermafrost develops after soil and rock have been below develops after soil and rock have been below

freezing for at least 2 consecutive yearsfreezing for at least 2 consecutive years Independent of moisture content of the soilIndependent of moisture content of the soil snow cover insulates the ground, preventing heat losssnow cover insulates the ground, preventing heat loss

Continuous and Discontinuous Zones of Continuous and Discontinuous Zones of permafrostpermafrost

Continuous ZoneContinuous Zone Permafrost occurs everywhere, continuously, throughout this Permafrost occurs everywhere, continuously, throughout this

regionregion Occurs pole-ward of the –7Occurs pole-ward of the –7ooC mean annual temperature C mean annual temperature

isothermisotherm Discontinuous ZoneDiscontinuous Zone

Occurs equator-ward of the –7Occurs equator-ward of the –7ooC mean annual temperature C mean annual temperature isothermisotherm

Permafrost becomes patchy and disconnected, becoming Permafrost becomes patchy and disconnected, becoming sparser at lower latitudes (mixed landscape of cryotic and sparser at lower latitudes (mixed landscape of cryotic and noncryotic soil)noncryotic soil)

Patches occur on slopes facing away from the sun (North slopes Patches occur on slopes facing away from the sun (North slopes in N. Hemisphere), cold soil, or areas not blanketed by snowin N. Hemisphere), cold soil, or areas not blanketed by snow

Permafrost behaviorPermafrost behavior Active layer: exposed to daily and Active layer: exposed to daily and

seasonal freezes and thawsseasonal freezes and thaws active layer thickens with increases in active layer thickens with increases in

temperaturetemperature Thawing releases carbon dioxide into the Thawing releases carbon dioxide into the

airair TaliksTaliks

areas of noncryotic soil within areas of areas of noncryotic soil within areas of continuous permafrostcontinuous permafrost

taliks form links with groundwater, permafrost taliks form links with groundwater, permafrost disrupts these linksdisrupts these links

Ground Ice and Frozen GroundGround Ice and Frozen Ground Refers to frozen subsurface waterRefers to frozen subsurface water

Pore IcePore Ice Lenses and VeinsLenses and Veins Segregated IceSegregated Ice Intrusive IceIntrusive Ice Wedge IceWedge Ice

Frost ActionFrost Action expansion of water as it freezes creates expansion of water as it freezes creates

physical forcesphysical forces Shatters rock, creating block fields or felsenmeerShatters rock, creating block fields or felsenmeer perturbs the soilsperturbs the soils

Frost heavingFrost heaving Frost thrustingFrost thrusting cryoturbationcryoturbation Ice wedgingIce wedging

LandformsLandforms Pingos: frozen injected artesian water, forming a Pingos: frozen injected artesian water, forming a

circular mound, sometimes up to 60 m in heightcircular mound, sometimes up to 60 m in height Palsas: Mounds of peat with ice lenses (1 – 10 m)Palsas: Mounds of peat with ice lenses (1 – 10 m) Patterned ground: heaving and thrusting of the soil Patterned ground: heaving and thrusting of the soil

sorts the particles according to texture, with sorts the particles according to texture, with accumulations in wedge cracks, forming polygonal accumulations in wedge cracks, forming polygonal patterns on the groundpatterns on the ground

Hillslope ProcessesHillslope Processes Active layer becomes saturated with water during Active layer becomes saturated with water during

thaw cycles, and a slow downhill flow can occurthaw cycles, and a slow downhill flow can occur solifluction, gelifluctionsolifluction, gelifluction

Thermokarst landscapesThermokarst landscapes Formed from melting ground ice with poor drainageFormed from melting ground ice with poor drainage cave-ins, bogs, depressions, standing water and cave-ins, bogs, depressions, standing water and

small lakessmall lakes not related to carbonated Karst topographynot related to carbonated Karst topography

The PleistoceneThe Pleistocene

1.8 million to 10,000 years ago1.8 million to 10,000 years ago Ice sheets and glaciers covered 1/3 of Earth’s Ice sheets and glaciers covered 1/3 of Earth’s

surfacesurface Periglacial regions occupied another 40% Periglacial regions occupied another 40%

The longest prolonged cold period in Earth’s The longest prolonged cold period in Earth’s historyhistory Ice Age: period of prolonged cold marked by Ice Age: period of prolonged cold marked by

significant periods of glacial advancesignificant periods of glacial advance glacials: 90,000 yearsglacials: 90,000 years interglacials: 10,000 yearsinterglacials: 10,000 years

Pleistocene included 18 glacialsPleistocene included 18 glacials

FeaturesFeatures Formation of the Great LakesFormation of the Great Lakes

Drainage systems enlarged by glacial actionDrainage systems enlarged by glacial action Two periods of advance and retreatTwo periods of advance and retreat

Charging of the Great Plains AquiferCharging of the Great Plains Aquifer Land BridgesLand Bridges

Lower temperatures caused more of Earth’s water to be tied up Lower temperatures caused more of Earth’s water to be tied up in icein ice

Sea levels were 100 meters lower than todaySea levels were 100 meters lower than today Exposed land, linking several continents, allowing for Exposed land, linking several continents, allowing for

movement of species, especially humansmovement of species, especially humans Bering Straits Land BridgeBering Straits Land Bridge England and FranceEngland and France Australia, New Guinea and IndonesiaAustralia, New Guinea and Indonesia

PaleolakesPaleolakes Advance of glaciers caused an advance of polar conditions, Advance of glaciers caused an advance of polar conditions,

subpolar lows and polar jet stream, bringing wetter conditions subpolar lows and polar jet stream, bringing wetter conditions further southfurther south

PluvialsPluvials InterpluvialsInterpluvials

Much of the American Southwest exhibited large lakes that are Much of the American Southwest exhibited large lakes that are now drynow dry

PaleoclimatologyPaleoclimatology The study of past climates and their change The study of past climates and their change

over timeover time Ice coresIce cores Ocean sedimentsOcean sediments pollen recordspollen records correlation of coral productivity to sea-level correlation of coral productivity to sea-level

changeschanges Humans evolved during the coldest parts of Humans evolved during the coldest parts of

Earth’s historyEarth’s history Recent FluctuationsRecent Fluctuations

Medieval Warm Period: 800 – 1200Medieval Warm Period: 800 – 1200 Little Ice Age: 1200 – 1350, 1800 - 1900Little Ice Age: 1200 – 1350, 1800 - 1900

Mechanisms of Climate ChangeMechanisms of Climate Change Variations in Earth-Sun relationsVariations in Earth-Sun relations

100,000 year cycle in variation of the shape of 100,000 year cycle in variation of the shape of Earth’s orbitEarth’s orbit

17.7 million km variation in Earth-Sun distance17.7 million km variation in Earth-Sun distance 26,000 year cycle in precession26,000 year cycle in precession

affects axial parallelismaffects axial parallelism 40,000 year cycle in axial tilt40,000 year cycle in axial tilt

varies between 22varies between 22oo and 24 and 24oo

Solar variability: variation in solar outputSolar variability: variation in solar output Tectonics: movement of continents between Tectonics: movement of continents between

latitudeslatitudes Atmospheric factorsAtmospheric factors

Volcanic eruptionsVolcanic eruptions Fluctuations in COFluctuations in CO22 content content

Oceanic CirculationOceanic Circulation Formation of the Isthmus of Panama 3 million years Formation of the Isthmus of Panama 3 million years

ago altered the patterns of ocean currents, area of ago altered the patterns of ocean currents, area of upwelling, and distribution of hot and cold ocean upwelling, and distribution of hot and cold ocean waterswaters