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LEDENJACI

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Antarktičkaledena kapa

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Grenlandskaledena kapa

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Sniježna granica:

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Snijeg

Zrnati snijeg

Firn

Ledenjački led

Prelazak snijega u ledenjački led zbog zatrpavanja

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Kako se ledenjak može kretati niz padinu i istovremeno na drugom kraju kretati uzbrdo?

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To ovisi o količini ledenjačkog leda kojiuključuje:

1) količinu ledenjačke akumulacije2) količinu ledenjačkog gubitka (ablacije)

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Ledenjačka zaliha

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Slijed povlačenja ledenjačkog šelfa

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Kada je ledenjačka akumulacija veća od ablacije, rezultat je rast

ledenjaka i pridružena ledenjačka erozija.

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Kada je ledenjačka akumulacija manja od ablacije, rezultat je

povlačenje ledenjaka i pridružena ledenjačka depozicija.

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Ledenjaci se kreću plastičnim

tokom i bazalnim klizanjem

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Plastični tok:

Ledenjaci u ledenjačkim dolinama uglavnom se kreću plastičnim tokom

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Bazalno klizanje:

Kontinentalni ledenjaci se kreću uglavnom bazalnim

klizanjem.

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Krivasi:

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165

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Morska razina ne raste ako se plutajući

led topi

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Morska razina raste ako se led topi na

kopnu

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Led polira ravne površine

Krivasi nastaju kretanjem ledenjaka preko stube (topografija temeljne stijene)

Led odlama dijelove stijene, proizvodeći grubu

površinu

Posljedica je oblik temeljne stijene roche

moutannée

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Prije glacijacije

Za vrijeme glacijacije Nakon glacijacije

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Erozijski oblici reljefa udruženi s glacijacijom doline

• doline oblika U• fjordovi• cirkete• arete• roche moutannées

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Vrste ledenjačkih taloga

• ledenjački drift:• ledenjački til:• eratički blokovi:• isprani talozi:

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Ledenjački drift:

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Taložni oblici udruženi s ledenjakom uključuju:

• ledenjačke morene– vršne morene– morene tla – bočne i središnje morene

• eskere• dramline• jezera u obliku kotla• ravnice ispranih taloga

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Središnjemorene

Bočnemorene

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Ledenjačkitalozi

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Za vrijeme otapanja leda

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Nakon potpunog otapanja

jezero uobliku kotla

dramlin

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Permafrost

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Rasprostiranje glacijacije na sjevernoj hemisferi, temeljeno na distribuciji glacijalnog drifta

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Rasprostiranje i debljina glacijalnog leda i temperature morske površine za tipičan dan u kolovozu, prije 18.000 god., u vrijeme zadnjeg ledenog doba.

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Izotopi kisika u marinskim mikrofosilima obilježavaju brojnaglacijalna i interglacijalna razdoblja

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Periodičnost glacijalnih i interglacijalnihciklusa je objašnjena cikličnim varijacijama Sunčeve energije,

upravljane periodičnim varijacijama:

• orbitalnoj ekscentričnosti• nagnutosti osi• precesiji osi ("vrludanje")

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Orbitalna ekscentričnost

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Nagnutost Zemljine osi

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Precesija

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Sustav oceanskih struja ima važan utjecaj na svjetsku klimu

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Dokazi nekadašnjih ledenih doba

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Gornjopaleozojski glacijalni talozi~350 mil. god.

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Gornjopaleozojski glacijalni talozi~350 mil. god.

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Gornjoprekambrijski glacijalni talozi~700 mil. god.

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Hipoteza o Zemlji kao sniježnoj kugli:

Postoje dokazi da se gornjoprekambrijska glacijacija pružala sve do ekvatorijalnih područja.

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