Outline GLACIERS 1)Types of glaciers 2)Glacier formation, movement 3)Glacial erosion 4)Glacial landforms and deposits 5)Side effects 6)Ice ages

OutlineGLACIERSGLACIERS

1)1) Types of glaciersTypes of glaciers

2)2) Glacier formation, movementGlacier formation, movement

3)3) Glacial erosionGlacial erosion

4)4) Glacial landforms and depositsGlacial landforms and deposits

5)5) Side effectsSide effects

6)6) Ice agesIce ages

1) Types of glaciers1) Types of glaciersGLACIERSGLACIERS

A Glacier Glacier is

part of hydrological cycle

thick iceice mass

formed on landland

made by snow: accumulationaccumulation

compaction compaction

recrystallizationrecrystallization

able to flowflow

...definition

GLACIERSGLACIERS



thick iceice mass

formed on landland




able to flowflow

...definition

Fig. 16.8

1) Types of glaciers1) Types of glaciersGLACIERSGLACIERS



thick iceice mass

formed on landland




able to flowflow

...definition

Valley (or “Alpine”) glaciers

Ice sheets

Ice capsIce caps

1) 1) TypesTypes of glaciers of glaciersGLACIERSGLACIERS

ice cover of plateaus smaller than ice sheets e.g., Iceland

large scale feature Greenland, Antarctica “continental ice sheets”

mountainous regions occupy old stream valleys length greater than width

Iceland

2) Glacier formation/movement2) Glacier formation/movementGLACIERSGLACIERS

Two types of movement flow

Plastic flow

Basal slip

Movement within the ice

Entire ice mass slips along ground

Zone of fracture: upper 50 m crevasses hereFig. Story 16.12

fastest in center of glacier

100’s m per year forward motion

surges


Rates of flowRates of flow

Frictional drag along sides slowsdown edges

Periods of rapid flow

Quite variable


glacier “budget”

snowline

zone of wastage

calving

Balance between accumulation at upper end & loss (“ablation”) at lower end

Net loss (melting)

Lower limit of “zone of accumulation”

Large ice pieces break offCreates icebergs whereglacier reaches the sea or a lake

Fig. 16.19

3) Glacial erosion3) Glacial erosionGLACIERSGLACIERS

2 ways:2 ways: pluckingplucking - glacier loosens/lifts/incorporates fractured rock



“erratics”



abrasionabrasion - glacier+rock fragments scrape over bedrock (like sandpaper), make rock flourrock flour

scrape marks on bedrock: glacial striations

give direction of flow

Fig. 16.17

4) Glacial landforms & deposits4) Glacial landforms & depositsGLACIERSGLACIERS

Valleys:Valleys:

Fig. 16.19

glacial troughglacial trough: U-shaped (from V-shaped)

hanging valleyshanging valleys: main glaciers cut deeper than side feeds

cirquescirques: bowl-shaped depressions at tops of U valleys

fiordfiord: steep-sided inlets to sea, drowned glacial troughs


Valleys:Valleys: glacial troughglacial trough: U-shaped (from V-shaped)

hanging valleyshanging valleys: main glaciers cut deeper than side feeds

cirquescirques: bowl-shaped depressions at tops of U valleys

fiordfiord: steep-sided inlets to sea


Arêtes:Arêtes: Sharp-edged ridges Sharp-edged ridges (close cirques, or parallel valleys)

Horns:Horns: Peaks left over after cirques enlargedPeaks left over after cirques enlarged


Aretes:Aretes: Sharp-edged ridges Sharp-edged ridges (close cirques, or parallel valleys)

Horns:Horns: Peaks left over after cirques enlargedPeaks left over after cirques enlarged

Matterhorn


““deposits”deposits”

Till glacierstratified drift melt water

Deposited by

dropped when ice meltsdropped when ice melts

10-100’s m thick10-100’s m thick

glacial drift - sediments of glacial drift - sediments of

glacial originglacial origin


Till landformsTill landforms MorainesMorainesend moraine: ridge of till at end of stable glacier

terminal moraine: outermost end moraine

ground moraine: from retreating glacier

lateral moraine: debris on side of glacier

medial moraine: from 2 glaciers joining


Till landformsTill landforms DrumlinsDrumlins Smooth elongated parallel hills


Stratified drift landformsStratified drift landforms outwash plainsoutwash plains

kettle lakeskettle lakes

eskerseskers


Stratified drift landformsStratified drift landforms outwash plainsoutwash plains

kettle lakeskettle lakes

eskerseskers

5) Side-effects5) Side-effectsGLACIERSGLACIERS

Ice retreat/advances:Ice retreat/advances: some animal/plant migration forcedsome extinctions

Stream flow changesStream flow changes

Isostatic reboundIsostatic rebound

Sea level changesSea level changes

Pluvial lakesPluvial lakes













See Fig. Story 16.16 + Box. 16.2, p. 371







If all Earth’s ice melted:

ancient Lake Bonneville

See Fig. Story 16.16 + Box. 16.2, p. 371

6) Ice ages6) Ice agesGLACIERSGLACIERS

Pleistocene: “Ice Age”: Last 1.8 million years17 cycles of cooling and warming

Older Ice Ages

Role of Plate tectonics

2.4 billion years ago2.4 billion years ago750-600 million years ago750-600 million years ago250 million years ago250 million years ago

Evidence from “tillites”

lithified glacial till, Fig. 16.29

Prof Agassiz

“The great ice age” (1830’s)

Heat flow from lower to arctic latitudes is interruptedFig. 16.29

6) Ice ages6) Ice agesGLACIERSGLACIERS

Earth orbit variations

Shape of orbit (more elliptical)Shape of orbit (more elliptical)

changes in tilt of rotation axischanges in tilt of rotation axis

wobbling of axiswobbling of axis

Milutin Milankovitch:

Earth orbit variations cause changes in the incoming solar radiation and are the principal factor in controlling Earth’s climate

Eccentricity; 100,000 yrs

Tilt; 41,000 yrs

Precession; 23,000 yrs

Other planets!Other planets!GLACIERSGLACIERS

Other Solar system objects have ice

MarsMars


Other Solar system objects have ice

EuropaEuropa

(A Jupiter moon)(A Jupiter moon)


MCsMCsGLACIERSGLACIERS

How thick are the Greenland and Antarctic ice caps?A. approximately 100 meters thickB. approximately 300 meters thickC. approximately 1 kilometer thickD. approximately 3 kilometers thick


Which of the following lists is written in order of increasing ice “metamorphism”?A. snow granular ice firn glacial iceB. snow firn glacial ice granular iceC. snow firn granular ice glacial iceD. snow granular ice glacial ice firn


Which of the following erosional features is characteristic of rivers and not glaciers?A. areteB. cirqueC. roche moutonéeD. V-shaped valley


If accumulation exceeds ablation, then __________.A. the glacial ice will flow downhill and the glacial front will move downhill B. the glacial ice will flow downhill, but the glacial front will move uphill C. the glacial ice will flow uphill, but the glacial front will move downhill D. the glacial ice will flow uphill and the glacial front will move uphill


Why do glacial crevasses form?A. because glacial meltwater erodes small valleys as glacial rivers flowB. because plate tectonic forces deform the glacierC. because the glacial surface deforms brittlely and cracks as the ice flowsD. because the glacial surface partially melts, leaving holes and cracks


If a very large iceberg in the ocean were to melt, what would happen to sea level?A. Sea level would decrease slightly.B. Sea level would remain the same.C. Sea level would increase slightly.D. Sea level would decrease or increase depending on the air content of the iceberg.


During the peak of the last ice age, sea level was ______ than sea level today.A. approximately 1 meter lowerB. approximately 10 meters lowerC. approximately 100 meters lowerD. approximately 1000 meters lower


When did the last ice age end?A. about 100 years agoB. about 10,000 years agoC. about 1 million years agoD. about 100 million years ago

Documents

Outline GLACIERS 1)Types of glaciers 2)Glacier formation, movement 3)Glacial erosion 4)Glacial landforms and deposits 5)Side effects 6)Ice ages