glaciers keynote
TRANSCRIPT
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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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