EOSC 110 Lecture Notes - Lecture 14: Silt
13 Jan 2017
School
Department
Course
Professor
Glacier:apermanentmassoficethatflowsdownslopeundertheinfluenceofgravity
• Currentlycover~10%ofEarth'sland
• 2%ofEarth'swater
• Advanceinmesofcoolerclimate
• Fouriceadvantagesinthelast2millionyears
○ 5‐10°colder
○ DuringlastIceAge,30%oflandcovered,10%ofwaterwasiceandsealeveldropped
100m
○ Ifallglaciersmeltedtoday‐‐>sealevelwouldrise60m
RequirementstoFormaGlacier
1. Accumulaonofsnowinwinter>melngofsnowinsummer
2. Compaconofaccumulatedsnowturnstoice
3. Icemustflowdownslope
• Thisisachievedathighlatudeorhighelevaon
• Ex:Mt.Kilimanjaro,Africa
HowdoGlaciersMove?
• Gravity=causeofglaciermoon
○ Iceslowlyformsandchangesinresponsetogravity
• Glaciermoldsitselftothelandandalsomoldsthelandasitcreepsdownthevalley
• Manyglaciersslideontheirbeds‐‐>enablingthemtomovefaster
• Rockthatfallsontoglacier'ssurfaceisincorporatedintotheglacieranderodesthebed‐‐>formingsediment
• Theglacieranditsloadofrockdebrisflowdown‐valley
• Aglacierdischargessnowfromitsaccumulaonareainthesamewayastreamdischargeswaterfromitswatershed
• Somemesincoldclimateswithalotofsnow(ex:Alaska),glaciersflowallthewaydowntosealevel
○ Theseglacierscarveordsandmakeicebergs
• Attheglacier'sface,icewhichhasbeenmelng,fracturingandhasbeenbaeredbytheseabreaksoffasicebergs
○ Thisprocessiscalledcalving‐‐>balancestheflowoficefrombehind
WhatCausesIceAges?
1. PerturbaonofEarth'sorbit
○Milankovitchcycles:changetheamountofheatfromsolarradiaonthatanyparcularpart
ofEarthreceives
2. GreenhouseEffect
○ IncreasedCO2intheatmospherecausesretenonofheat
○ DecreasedCO2decreasesretenonofheat
3. PlateTectonics
○ Volcanoes
○ Ratesofplatemovement
○ Posionsofconnents
○ Connentaleffectsonoceancirculaon
EvidenceofGlaciaon
• Glaciers=highlyerosive
○Glacialerosion:
•Glacialpolish
EvidenceofGlaciaon
Glacialsediments:
•Till:poorlysorted,mixofallgrainsizes,dumpedfromendofglacier
Glaciers
Saturday,November5,2016 7:02PM
Document Summary
I(cid:272)e slo(cid:449)ly forms a(cid:374)d (cid:272)ha(cid:374)ges i(cid:374) respo(cid:374)se to gravity: gla(cid:272)ier molds itself to the la(cid:374)d a(cid:374)d also molds the la(cid:374)d as it (cid:272)reeps do(cid:449)(cid:374) the valley, ma(cid:374)y gla(cid:272)iers slide o(cid:374) their beds > e(cid:374)abli(cid:374)g them to move faster, ro(cid:272)k that falls o(cid:374)to gla(cid:272)ier"s surfa(cid:272)e is i(cid:374)(cid:272)orporated i(cid:374)to the gla(cid:272)ier a(cid:374)d erodes the bed > formi(cid:374)g sedime(cid:374)t, the gla(cid:272)ier a(cid:374)d its load of ro(cid:272)k debris o(cid:449) do(cid:449)(cid:374) valley, a gla(cid:272)ier dis(cid:272)harges s(cid:374)o(cid:449) from its a(cid:272)(cid:272)umula(cid:415)o(cid:374) area i(cid:374) the same (cid:449)ay a stream dis(cid:272)harges (cid:449)ater from its (cid:449)atershed, some(cid:415)mes i(cid:374) (cid:272)old (cid:272)limates (cid:449)ith a lot of s(cid:374)o(cid:449) (cid:894)e(cid:454): alaska(cid:895), gla(cid:272)iers o(cid:449) all the (cid:449)ay do(cid:449)(cid:374) to sea level. Glacial sedi(cid:373)e(cid:374)ts: till: poorly sorted, mi(cid:454) of all grai(cid:374) sizes, dumped from e(cid:374)d of gla(cid:272)ier, st(cid:396)ia(cid:415)o(cid:374)s, g(cid:396)oo(cid:448)es, out(cid:449)ash: uvial stream deposits, sorted a(cid:374)d stra(cid:415) ed, by melt(cid:449)ater (cid:894)de (cid:272)ie(cid:374)t streams(cid:895, rock ou(cid:396, ti(cid:374)y par(cid:415)(cid:272)les (cid:272)ha(cid:374)ge the (cid:272)olour, gla(cid:272)iers (cid:272)reate dis(cid:415)(cid:374)(cid:272)t & beau(cid:415)ful la(cid:374)ds(cid:272)apes, u shaped valley.
