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