G110 13 Glacial Geology Depos.

8/8/2019 G110 13 Glacial Geology Depos.

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Paths of Glacial TransportPaths of Glacial Transport

Supraglacial all the waySupraglacial all the way

Supraglacial to englacialSupraglacial to englacialto supraglacialto supraglacial

Subglacial all the waySubglacial all the way Subglacial to englacialSubglacial to englacial

to supraglacialto supraglacial

Which path will have theWhich path will have the

greatest effect ongreatest effect onabrasion of transportedabrasion of transportedclasts?clasts?


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Types of Glacial DepositsTypes of Glacial Deposits

DriftDrift: all deposits in any way related to: all deposits in any way related toglaciation.glaciation.

TillTill: unstratified drift carried and: unstratified drift carried anddeposited by the ice.deposited by the ice.

Stratified driftStratified drift: water has played a role in: water has played a role indeposition.deposition.Types are:Types are: Glaciofluvial:Glaciofluvial: by meltwater streamsby meltwater streams

Glaciolacustrine:Glaciolacustrine: in glacial lakesin glacial lakes Glaciomarine:Glaciomarine: in the oceanin the ocean


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Types of TillTypes of Till -- ProcessesProcesses

Lodgement TilllLodgement Tilll FlowFlowTillTill

Lodgement till and subglacialLodgement till and subglacialflow till.flow till.


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Depositional LandformsDepositional Landforms

MorainesMoraines

Moraines without ridgelike form:Moraines without ridgelike form:

ground moraineground moraine

flat to rolling, hummocky terrainflat to rolling, hummocky terrain

predominantly lodgment tillpredominantly lodgment tilloverlain by ablation tilloverlain by ablation till


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Note areaNote area

of groundof groundmorainemoraine(GM)(GM)


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Note groundNote groundmorainemoraine


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Moraines (cont.)Moraines (cont.)

Moraines without ridgelike form:Moraines without ridgelike form:

disintegration morainedisintegration moraine::

moderately rugged terrain ofmoderately rugged terrain ofchaotic mounds and pits (chaotic mounds and pits (kameskames andand kettles)kettles)formed by the downwasting offormed by the downwasting of

stagnant icestagnant ice

sediments a mixture of ablation till, glaciofluvialsediments a mixture of ablation till, glaciofluvialdeposits, and glaciolacustrine deposits.deposits, and glaciolacustrine deposits.


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NoteNote

disintegrationdisintegrationmorainemoraine..


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Note disintegration moraine in right halfNote disintegration moraine in right halfof area.of area.


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Moraines (cont.)Moraines (cont.)moraines with ridgemoraines with ridge--like formlike form

lateral moraineslateral moraines andand medialmedial

moraines (alpine terrain)moraines (alpine terrain) most prominent where the valley is notmost prominent where the valley is not

too restrictivetoo restrictive

debris from within the glacier due todebris from within the glacier due tolaterallateral flow or may be massflow or may be mass--wastedwasted

How would the latter be related toHow would the latter be related to slopeslope

aspect?aspect?


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Note lateralNote lateralmoraine.moraine.


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Moraines (cont.)Moraines (cont.)

medial moraines:medial moraines:

form from the merger of two alpine glaciers andform from the merger of two alpine glaciers and

their lateral morainestheir lateral moraines

traced downglacier, often merge with a cover oftraced downglacier, often merge with a cover of

ablation till resting on the iceablation till resting on the ice

rarely preserved when the ice melts. Why wouldrarely preserved when the ice melts. Why would

that be?that be?


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Medial Moraines


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Depositional LandformsDepositional LandformsMoraines (cont.)Moraines (cont.)

end moraine: terminal moraine:end moraine: terminal moraine:any moraine builtany moraine built marks outermostmarks outermost

around the marginaround the margin advance of glacieradvance of glacierof a glacier.of a glacier. during aduring a

particular glacialparticular glacialrecessional morainerecessional moraine stage (onlu onestage (onlu onemarks position ofmarks position of terminal moraine canterminal moraine can

pauses or readvancespauses or readvances exist).exist).

during time of overallduring time of overall


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Note end and

Note end andlaterallateral

moraines.moraines.


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NoteNote

terminalterminalmorainemoraineandandrecess.recess.morainemoraine


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Note terminal and recessionalNote terminal and recessional

morainesmoraines..


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Streamlined FormsStreamlined Forms

DrumlinsDrumlins Elliptically elongated hills parallel to flowElliptically elongated hills parallel to flowdirection.direction.

Dimensions of < 150 ft high, 1/3 to 1/2Dimensions of < 150 ft high, 1/3 to 1/2

milemile long.long. Blunt end upglacier, tapered downglacier.Blunt end upglacier, tapered downglacier.

Composed mostly of till, but may haveComposed mostly of till, but may havecorecore of bedrock, waterlaid materialof bedrock, waterlaid material

(deformed)(deformed)

Usually located several miles back fromUsually located several miles back from

icemargin in clusters. Why?icemargin in clusters. Why?


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NoteNote

drumlins.drumlins.(DR).(DR).


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NoteNotedrumlinsdrumlins


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Glaciofluvial DepositsGlaciofluvial DepositsProcesses of DepositionProcesses of Deposition

Deposition either:Deposition either:

In direct contact (iceIn direct contact (ice--contact)contact) with the icewith the ice or some distance beyond the ice (or some distance beyond the ice (proglacialproglacial))

Processes of fluvial deposition mostProcesses of fluvial deposition mostcommoncommon

Sometimes flow is in tunnels or otherSometimes flow is in tunnels or otheropenings in the ice where water may beopenings in the ice where water may beunder pressure.under pressure.


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Glaciofluvial DepositsGlaciofluvial Deposits

Distinguishing CharacteristicsDistinguishing Characteristics Clasts roundedClasts rounded

Usually unimodal grain size (fines removed)Usually unimodal grain size (fines removed) Bedding, some rather crudeBedding, some rather crude

Often crossOften cross--beddedbedded

GrainGrain--toto--grain contactgrain contact

Imbrication possible, may reveal flow dir.Imbrication possible, may reveal flow dir.


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IceIce--Contact LandformsContact LandformsConsiderations andConsiderations and

CharacteristicsCharacteristics

Ice on at least one sideIce on at least one side

Extreme range and abrupt changes inExtreme range and abrupt changes ingrain sizegrain size

Clasts less abraded than in proglacialClasts less abraded than in proglacialdepositsdeposits

May include bodies of tillMay include bodies of till Slumping commonSlumping common


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Glaciofluvial IceGlaciofluvial Ice--ContactContactLandformsLandformsKame TerracesKame Terraces

Short, narrow benches along valley wall ofShort, narrow benches along valley wall ofglaciated valleys.glaciated valleys.

Surface often pitted with kettles.Surface often pitted with kettles. Accumulations of streams that flowedAccumulations of streams that flowed

between glacier and valley wall.between glacier and valley wall. Ice usually stagnant.Ice usually stagnant. Left as terraces when ice melted.Left as terraces when ice melted.


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NoteNotekame terrackame terrac(KT)(KT) andandkames (K)kames (K)


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Note kame terrace (KT)Note kame terrace (KT)and kames (K).and kames (K).


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Glaciofluvial IceGlaciofluvial Ice--ContactContact

LandformsLandformsKamesKames Moundlike hill.Moundlike hill.

Formation may be as sediment is deposited inFormation may be as sediment is deposited increvasses in or on the surface of stagnant ice.crevasses in or on the surface of stagnant ice.

Or, where small deltas or fans build against theOr, where small deltas or fans build against theice.ice.

Debris collapses to form mound when ice melts.Debris collapses to form mound when ice melts. May be found in kameMay be found in kame--andand--kettle moraines.kettle moraines.

See previous illlustrations.See previous illlustrations.


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LandformsLandforms --EskersEskers

Long, narrow commonly sinuous ridges.Long, narrow commonly sinuous ridges.

May connect downvalley with deltas.May connect downvalley with deltas.

Overall trend parallels the direction of iceOverall trend parallels the direction of iceflow.flow.

May climb over low ridges. How can it be?May climb over low ridges. How can it be? Slumping may occur along sides.Slumping may occur along sides.

Mostly sand & gravel, but with lenses ofMostly sand & gravel, but with lenses oftill.till.


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LandformsLandformsEskers (cont.)Eskers (cont.)

They are deposits of streams inThey are deposits of streams intunnels. Probably stagnant icetunnels. Probably stagnant ice

Can you reconstruct what it was likeCan you reconstruct what it was like

when the glacier was forming?when the glacier was forming?


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Note esker.Note esker.Note esker.Note esker.


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NoteNoteeskeresker


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NoteNote

esker.esker.(E).(E).


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Proglacial LandformsProglacial LandformsCharacteristicsCharacteristics

Composed of outwash; coarseComposed of outwash; coarse--grainedgraineddeposits of streams beyond the icedeposits of streams beyond the icemargins.margins.

Usually the deposits of braided streams.Usually the deposits of braided streams.

WellWell--sorted to poorlysorted to poorly--sorted.sorted.

Many variations in grain size, but generallyMany variations in grain size, but generallya decrease downstream.a decrease downstream.

Silt, clay minor or absent.Silt, clay minor or absent. Rounding of clasts, especially boulders andRounding of clasts, especially boulders and

cobbles.cobbles.


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ProglaccialOutwashProglaccialOutwash

FeaturesFeaturesOutwash PlainsOutwash Plains vs.vs. Valley TrainsValley Trains

ConsiderableConsiderablelateral extentlateral extent

Usually in lowlandsUsually in lowlands

Banked against endBanked against endof glacierof glacier

May be fanMay be fan--shapedshaped

Confined by valleyConfined by valleywallswalls

Long and linear orLong and linear or

sinuoussinuous


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NoteNote

autwashautwashplain (OP)plain (OP)and kettlesand kettles(KL).(KL).


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Note disintegration moraine in right halfNote disintegration moraine in right halfof area. Note outwash plain and kettles.of area. Note outwash plain and kettles.


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OutwashOutwashplain is aplain is avvalleyvvalley

train.train.


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Glaciolacustrine FeaturesGlaciolacustrine Features

GlacialLakesGlacialLakes

In erosional basins: cirques (tarns),In erosional basins: cirques (tarns),

rock basins in glacial troughs, etc.rock basins in glacial troughs, etc. Behind morainesBehind moraines

Kettle lakesKettle lakes

Any more?Any more?


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Glaciolacustrine FeaturesGlaciolacustrine Features

KettlesKettles

Basin where ice block was surroundedBasin where ice block was surroundedby sediments.by sediments.

Occur singly or in groups.Occur singly or in groups.


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GlacialG

lacial--Lake SedimentsLake Sediments Delta: coarse sediments, steep crossDelta: coarse sediments, steep cross--

beddingbedding

Bottom deposits: mostly silt and clay;Bottom deposits: mostly silt and clay;usually laminated, may be varved. Whatusually laminated, may be varved. Whatare varves?are varves?

M

ay include dropstonesM

ay include dropstones Shore features: waveShore features: wave--cut cliffs, beachcut cliffs, beachdeposits, etc.deposits, etc.


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Note proglacialNote proglaciallake and kettlelake and kettlelakes.lakes.


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Note outwash plain, kettles,Note outwash plain, kettles,and proglacial lake.and proglacial lake.


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Terms needed for the

study of glacial geologyAbrasion

Arete

CirqueCirque aspect

Col

Drift

Dropstone

Drumlin

End moraine

Esker

Flow till

FacetGlacial lake

Glacial steps

Glaciofluvial

Glaciolacustrine

Glaciomarine

Grooves


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study of glacial geologyIce-contact deposit

Ice-push moraine

KameKame terrace

Kettle

Lateral moraine

Lodgment till

Medial moraine

Megagroove

Melt-out till

Nivation hollow

Outwash

Outwash plainPater noster lakes

Polish

Proglacial deposits

Proglacial lake

Recessional moraine

Regelation

Roche moutonee


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study of glacial geologyRock basin

Rock drumlin

Rock flour

Stratified drift

Striations

Tarn

Terminal moraine

Till

Valley train

Whaleback


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Student Responsibilities on

Glacial Geology

Know the processes of glacial erosion andKnow the processes of glacial erosion and

the features they produce. Especiallythe features they produce. Especiallyfocus on glacial landforms of alpinefocus on glacial landforms of alpineareas, such as glacial troughs andareas, such as glacial troughs andcirques. Know about the different typescirques. Know about the different types

of glacial deposits and depositionalof glacial deposits and depositionallandforms. Especially focus on moraineslandforms. Especially focus on morainesof various types and glaciofluvial andof various types and glaciofluvial andglaciolacustrine depositsglaciolacustrine deposits..


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G110 13 Glacial Geology Depos.

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