glaciers keynote

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    GlaciersBy Mrs. Heinke

    All photos taken by Mr. and Mrs. Heinke atGlacier National Park

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    Grinnell Glacier

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    What are Glaciers?

    Masses of moving iceon land

    Forms when snow

    falls and freezesfaster than it canmelt. Snow freezesto ice, more snowfalls and freezes toice, building up into alarge mass of ice.

    Pressure on thelower layers causesmelting, which actsas a lubricant for the

    glacier, causing it tomove

    Speed of glacierdepends on frictionbetween the ice androck

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    How do Glaciers move?Plastic flow- the icedeforms because ofpressure- more of anoozing movement

    Basal Sliding- thelowest layer meltscompletely, and the

    glacier slips on liquidwater- more of asliding movement

    Slowly- between andinch and a couplefeet per day(depends on friction)

    Retreats andAdvances- oftenmoves back and forth

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    U-Shaped Valley

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    U-Shaped ValleyAs glaciers move through

    mountain valleys, theywiden and deepen thevalleys into a U-shape.Glaciers smooth the

    valley floor and wallsthrough Plucking.Plucking is when bedrocksticks to the glacier and is

    pulled from the mountain.

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    CirqueForms through a process offreezing, thawing, and plucking.The freeze-thaw cycle breaksdown the rock and causes

    avalanches, which causes theglacier to grow.The thawing causes theglacier to move, which plucks

    away the sides of themountain.

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    How many cirques do you see?

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    Cracker Lake cirque

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    Ptarmigan Wall- an Arete

    Created when twoglaciers erode back toback on either side of a

    mountain.

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    HorneSimilar to an areteThe glaciers circle

    part of the mountainand continue pluckinguntil all that is left isa horne.

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    Glacial TillRocks plucked from themountain by the glacier

    Till moves with theglacier until it is droppedthrough melting

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    MoraineA build-up of glacial

    till deposited by theglacierTerminal morainesare formed at the endof the glaciers path-lets geologists knowhow far a glaciermovedLateral moraines are

    formed on the sides ofthe glaciers path

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    Glacial Abrasion (scraping)

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    Glacial Striation and Chatter MarksCaused by abrasionGlacial till that iscarried with the glacierscrapes against thebedrock, which is visible

    as striationsLarger pieces of tillwill leave gouges, orchatter marks, in thebedrock from skipping

    over the bedrock

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    Glacial FlourCreated by glacial abrasionAs the till scrapes against thebedrock, it grinds the rock intofine particles, much like flour

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    Glacial LakesGlacial flour makes its wayinto streams and lakesThe water appears

    brilliantly blue as a result ofthe way light reflects offthe flour

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