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Mysterious rock Mysterious rock formations…….formations…….
What could have caused What could have caused these formations?these formations?
GLACIERS!!!!!GLACIERS!!!!!
Evidence for GlaciersEvidence for Glaciers
ErraticsErraticsUnsorted materialUnsorted materialStriationsStriationsPolished BedrockPolished Bedrock
Erratic
ErraticErratic
Boulder-sized rock Boulder-sized rock dumped by a dumped by a glacierglacier
Rock is different Rock is different type than type than surrounding rockssurrounding rocks
Unsorted Unsorted Materials-Materials-all sizes all sizes mixed mixed
together.together.
Striations
Chatter marks(Maine)
Striations/ Chatter marksStriations/ Chatter marks
Grooves carved Grooves carved into bedrockinto bedrock
Formed by Formed by abrasive action of abrasive action of cobbles and cobbles and pebbles carried at pebbles carried at bottom of glacierbottom of glacier
Direction of Direction of scratches shows scratches shows direction glacier direction glacier movedmoved
Glacial polishGlacial polish
Smooth rock Smooth rock surfacessurfaces
Created as glaciers Created as glaciers flow over bedrockflow over bedrock
Glacial Pavement….Glacial Pavement….
What does a glacier look like?What does a glacier look like?
What conditions are necessary for What conditions are necessary for glacial formation?glacial formation?
Cold Summers!!Cold Summers!!Located above the snow line, or in Located above the snow line, or in
polar regions.polar regions.Presently occupy 10 % of world’s total Presently occupy 10 % of world’s total
land area (32% during ICE AGES)land area (32% during ICE AGES)Form on all continents BUT AustraliaForm on all continents BUT Australia
Process of Glacier FormationProcess of Glacier Formation
Snow does NOT melt in summerSnow does NOT melt in summerRecrystallization of snow to form LARGE Recrystallization of snow to form LARGE
crystals of ice (rough and granular)crystals of ice (rough and granular)
–called FIRN: liked packed snowballscalled FIRN: liked packed snowballsLower layers turn to SOLID ICE under the Lower layers turn to SOLID ICE under the
weight of overlying firn and snow.weight of overlying firn and snow.
Snow becomes Firn
Glaciers: Glaciers: TypesTypes VALLEY GLACIERSVALLEY GLACIERS: :
long, slow-moving, long, slow-moving, wedge-shaped wedge-shaped streams of ice streams of ice
Bordered by Bordered by mountainsmountains
Size varies*Size varies*
small= 1-2 km long, 100’s m wide, 100’s m small= 1-2 km long, 100’s m wide, 100’s m deep*deep*
largest = Over 100km’s long X 100’s m deeplargest = Over 100km’s long X 100’s m deep
CONTINENTAL GLACIERCONTINENTAL GLACIER (ICE SHEETS): (ICE SHEETS): very old (1000’s of years) and thick (1000’s very old (1000’s of years) and thick (1000’s
of meters) of meters) Not confined by mountainsNot confined by mountains
Examples:Examples:GREENLANDGREENLAND: 1.7 million square miles, 2 miles : 1.7 million square miles, 2 miles
thickthickANTARCTICAANTARCTICA: 12.5 million square miles, 3 miles : 12.5 million square miles, 3 miles
thickthick
Features associated with Features associated with valley (alpine) glaciersvalley (alpine) glaciers
Original valley (V-shaped)
Glaciers come and alter landforms
Glaciers retreat and newfeatures appear
Landscape Features- Landscape Features- Valley GlaciersValley Glaciers
CIRQUESCIRQUES: : semi-circular shaped bedrock feature semi-circular shaped bedrock feature created as a glacier scours back toward the mountaincreated as a glacier scours back toward the mountain
ARÊTESARÊTES: : steep-sided, sharp-edged bedrock ridgesteep-sided, sharp-edged bedrock ridge formed by two glaciers eroding away formed by two glaciers eroding away
on opposite sides of a ridgeon opposite sides of a ridge
CIRQUE
TARN
TARNS:TARNS:glacial lakes glacial lakes produced by glacial scouringproduced by glacial scouringoften found in cirquesoften found in cirques
HORNSHORNS:: 3 or more cirques adjacent to one 3 or more cirques adjacent to one
anotheranother
Hanging Valley
ARÊTE CIRQUE
HANGING VALLEY
U-SHAPED VALLEY
U-shaped valley
CONTINENTAL GLACIERS CONTINENTAL GLACIERS FEATURESFEATURES
Lateral moraine
MORAINESMORAINES: material left behind : material left behind when glacier recedeswhen glacier recedes
When glacier retreats (melts) rock and When glacier retreats (melts) rock and sediments are dropped behindsediments are dropped behind
Long Island, Cape Cod and the islands are Long Island, Cape Cod and the islands are part of a part of a terminal moraineterminal moraine
Kettle Lake
Till
Drumlins
Terminal Moraine
Glacial Stream
Moraine-dammed lake
Outwash
plain
Esker
Drumlin
drumlins
Kettle Lakes
River in glacier carries sediment
Glacier meltsDrops sediment
Esker results
Eskers