• Glacier > a mass of ice composed of recrystallizedcompacted snow that flows under its ownweight on land.

• Presently glaciers cover of theEarth's surface.

• Glaciers occur in Greenland andAntarctica and in higher mountainranges.

• Glacier > a mass of ice composed of recrystallizedcompacted snow that flows under its ownweight on land.

• Presently glaciers cover of theEarth's surface.

• Glaciers occur in Greenland andAntarctica and in higher mountainranges.

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Glaciers and Glaciation Glaciers and Glaciation

Glaciers-

Important in understanding global scale climate change

Related to all 5 of the Earth’s systems

Exosphere- changes in the amount of sunlight cause glaciations

Hydrosphere- glacial ice is frozen water, part of the hydrosphere

Geosphere- Glacial ice flows over and modifies land

Atmosphere- alteration of global atmospheric patterns contributes to glacial ice formation

Biosphere- ice displaces animals and plants

Glaciers-

Important in understanding global scale climate change

Related to all 5 of the Earth’s systems

Exosphere- changes in the amount of sunlight cause glaciations

Hydrosphere- glacial ice is frozen water, part of the hydrosphere

Geosphere- Glacial ice flows over and modifies land

Atmosphere- alteration of global atmospheric patterns contributes to glacial ice formation

Biosphere- ice displaces animals and plants

• Glacial times represent significant timeperiods in Earth's history

• Represent major climatic departuresfrom the modern on a Global Scale

• Cyclic in Nature

• Man's Influence???

• Glacial Ice contains records ofatmospheric changes

• Glacial times represent significant timeperiods in Earth's history

• Represent major climatic departuresfrom the modern on a Global Scale

• Cyclic in Nature

• Man's Influence???

• Glacial Ice contains records of past atmospheric changes

Importance

Proterozoic, Pennsylvanian, Pleistocene

• Snowflakes are melted & deformed by the pressure ofoverlying snow, becoming granular snow, then firn, andfinally interlocking crystals of glacial ice.

Origin of ice

Descriptive classification of GlaciersDescriptive classification of Glaciers

• Valley (or Alpine) Glaciers are confinedto mountain valleys.> may eventually cover the entire mountain rangebecoming a mountain ice sheet

> may also spill onto low flatlands becomingPiedmont glaciers

• Continental (or Ice Sheets) > cover vast areas of more than 50,000 km .Today, continental glaciers are only found inGreenland and Antarctica.

> Not so in the geological past

• Valley (or Alpine) Glaciers are confinedto mountain valleys.> may eventually cover the entire mountain rangebecoming a mountain ice sheet

> may also spill onto low flatlands becomingPiedmont glaciers

• Continental (or Ice Sheets) > cover vast areas of more than 50,000 km .Today, continental glaciers are only found inGreenland and Antarctica.

> Not so in the geological past

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Response of a Glacier to Changes in Glacial BudgetIf accumulation = ablation, then no advance or retreat, but continues to flowIf accumulation > ablation, then glacier advances while flowingIf accumulation < ablation, then glacier retreats, but continues to flow

Effects of GlaciersEffects of Glaciers

• Fills in the low spots> valleys and basins get filled in w/ sediment

• Knocks down the high spots> mountains and hills get eroded

• Reroutes the drainages> valley filling may block streams, causingnew paths to be taken

• Deposits accumulate in specificplaces related to flow and meltwatercharacteristics

• Fills in the low spots> valleys and basins get filled in w/ sediment

• Knocks down the high spots> mountains and hills get eroded

• Reroutes the drainages> valley filling may block streams, causingnew paths to be taken

• Deposits accumulate in specificplaces related to flow and meltwatercharacteristics

• James Lobe and Glacial Lake Agassiz

Erosional ProcessesErosional Processes

･ Important erosionalprocesses associatedwith glaciers includeplucking, abrasion, andbulldozing.

･ Plucking and abrasionare most common> can form a landformcalled a rochemoutonnee

･ Important erosionalprocesses associatedwith glaciers includeplucking, abrasion, andbulldozing.

･ Plucking and abrasionare most common> can form a landformcalled a rochemoutonnee

Erosional featuresRoche Moutonnée

Erosional featuresRoche Moutonnée

Erosional features•Hanging Valley•Horn•Arete•Cirque•U-shaped trough•Col•Truncated Spurs

Erosional features•Hanging Valley•Horn•Arete•Cirque•U-shaped trough•Col•Truncated Spurs

Glacial DepositsGlacial Deposits• glacial drift- A general termrefering to sediment formed by anyglacial action.

• Till (Diamicton) poorly sorted,unlayered material directly

deposited by a glacier;• Stratified drift (Outwash) sorted,layered sediment usuallydeposited by meltwater streams.

• glacial drift- A general termreferring to sediment formed byAny glacial action.

• Till (Diamicton) poorly sorted,unlayered material directlydeposited by a glacier; ice contact

• Stratified drift (Outwash) sorted,layered sediment usuallydeposited by meltwater streams.Proglacial or ice contact

A glacial erraticDepositional features- glacial erratic

6 ft6 ft

Yellowstone ParkYellowstone Park

Sediments-Glacial Till exposed in IowaSediments-Glacial Till exposed in Iowa

Moraine formation- made of Till, deposited by iceDepositional features- moraines

Moraine formation- made of Till, deposited by iceDepositional features- moraines

Moraine formation- made of Till, deposited by iceDepositional features- moraines

･ Lateral and MedialMoraines are sedimenteroded from the valleysides and deposited bya glacier. They oftenappear as dark stripesin a glacier.

･ Lateral and MedialMoraines are sedimenteroded from the valleysides and deposited bya glacier. They oftenappear as dark stripesin a glacier.

LateralmorainesLateralmoraines

Medial morainesMedial moraines

Depositional features- distribution of moraines

Depositional features- Kames, eskers, kettle lakes, drumlins, outwash plain (sandur)

Depositional features- Kames, eskers, kettle lakes, drumlins, outwash plain (sandur)

Outwash with kettles

Kettle lakesKettle lakes

OutwashOutwash

morainemoraine

Kame terraceKame terrace

Outwash Plain with eskers and a braided stream

Outwash Plain with eskers and a braided stream

Pleistocene GlaciationPleistocene Glaciations

• The Pleistocene "ice age" began~1.96 million years ago • Several glacial and interglacialepisodes.> Glacial - a period of ice advance, generallyinterpreted as a globally cool period.

> Interglacial - a period of ice retreat, generallyinterpreted as a globally warm period.

• The Pleistocene "ice age" began~1.96 million years ago • Several glacial and interglacialEpisodes have occurred.> Glacial - a period of ice advance, generallyinterpreted as a globally cool period.

> Interglacial - a period of ice retreat, generallyinterpreted as a globally warm period.

We are in an interglacial period right now

Milankovich Orbital Theory Milankovitch Orbital Theory • Proposed to account for the cyclicalnature of Glaciations.

• Astronomer & Mathematician MilutinMilankovich attributed the glaciation tovariation in three parameters of theEarth's orbit.

• Proposed to account for the cyclicalnature of Glaciations.

• Astronomer & Mathematician MilutinMilankovitch attributed the glaciation tovariation in three parameters of theEarth's orbit.

eccentricity

precessionprecession

Obliquity- not shownObliquity- not shown

warmwarmwarmwarm

coldcold coldcold

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Erie Lobe