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
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
Fig. 16.8
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
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
2) Glacier formation/movement2) Glacier formation/movementGLACIERSGLACIERS
Rates of flowRates of flow
Frictional drag along sides slowsdown edges
Periods of rapid flow
Quite variable
2) Glacier formation/movement2) Glacier formation/movementGLACIERSGLACIERS
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
3) Glacial erosion3) Glacial erosionGLACIERSGLACIERS
2 ways:2 ways: pluckingplucking - glacier loosens/lifts/incorporates fractured rock
“erratics”
3) Glacial erosion3) Glacial erosionGLACIERSGLACIERS
2 ways:2 ways: pluckingplucking - glacier loosens/lifts/incorporates fractured rock
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
4) Glacial landforms & deposits4) Glacial landforms & depositsGLACIERSGLACIERS
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
4) Glacial landforms & deposits4) Glacial landforms & depositsGLACIERSGLACIERS
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
4) Glacial landforms & deposits4) Glacial landforms & depositsGLACIERSGLACIERS
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
4) Glacial landforms & deposits4) Glacial landforms & depositsGLACIERSGLACIERS
““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
4) Glacial landforms & deposits4) Glacial landforms & depositsGLACIERSGLACIERS
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
4) Glacial landforms & deposits4) Glacial landforms & depositsGLACIERSGLACIERS
Till landformsTill landforms DrumlinsDrumlins Smooth elongated parallel hills
4) Glacial landforms & deposits4) Glacial landforms & depositsGLACIERSGLACIERS
Stratified drift landformsStratified drift landforms outwash plainsoutwash plains
kettle lakeskettle lakes
eskerseskers
4) Glacial landforms & deposits4) Glacial landforms & depositsGLACIERSGLACIERS
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
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
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
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
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 planets!Other planets!GLACIERSGLACIERS
Other Solar system objects have ice
EuropaEuropa
(A Jupiter moon)(A Jupiter moon)
Other planets!Other planets!GLACIERSGLACIERS
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
MCsMCsGLACIERSGLACIERS
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
MCsMCsGLACIERSGLACIERS
Which of the following erosional features is characteristic of rivers and not glaciers?A. areteB. cirqueC. roche moutonéeD. V-shaped valley
MCsMCsGLACIERSGLACIERS
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
MCsMCsGLACIERSGLACIERS
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
MCsMCsGLACIERSGLACIERS
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.
MCsMCsGLACIERSGLACIERS
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
MCsMCsGLACIERSGLACIERS
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
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