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

2. 1) Types of glaciers GLACIERS Glacier A Glacier is l part of hydrological cycle ice l thick ice mass land l formed on land l made by snow: Ù accumulation Ù compaction Ù recrystallization flow l able to flow...definition

3. GLACIERS Glacier A Glacier is l part of hydrological cycle ice l thick ice mass land l formed on land l made by snow: Ù accumulation Ù compaction Ù recrystallization flow l able to flow...definition Fig. 16.8

4. 1) Types of glaciers GLACIERS Glacier A Glacier is l part of hydrological cycle ice l thick ice mass land l formed on land l made by snow: Ù accumulation Ù compaction Ù recrystallization flow l able to flow...definition

5. l Valley (or “Alpine”) glaciers l Ice sheets Ice caps l Ice caps 1) Types of glaciers GLACIERS Ù ice cover of plateaus Ù smaller than ice sheets Ù e.g., Iceland Ù large scale feature Ù Greenland, Antarctica Ù “continental ice sheets” Ù mountainous regions Ù occupy old stream valleys Ù length greater than width Iceland

6. 2) Glacier formation/movement GLACIERS Two types of movement flow l Plastic flow l Basal slip Movement within the ice Entire ice mass slips along ground Zone of fracture: upper 50 m crevasses here Fig. Story 16.12

7. l fastest in center of glacier l 100’s m per year forward motion l surges 2) Glacier formation/movement GLACIERS Rates of flow Frictional drag along sides slows down edges Periods of rapid flow Quite variable

8. 2) Glacier formation/movement GLACIERS l glacier “budget” l snowline l zone of wastage l 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 off Creates icebergs where glacier reaches the sea or a lake Fig. 16.19

9. 3) Glacial erosion GLACIERS 2 ways: plucking plucking - glacier loosens/lifts/incorporates fractured rock

10. 3) Glacial erosion GLACIERS 2 ways: plucking plucking - glacier loosens/lifts/incorporates fractured rock “erratics”

11. 3) Glacial erosion GLACIERS 2 ways: plucking plucking - glacier loosens/lifts/incorporates fractured rock abrasion abrasion - glacier+rock fragments scrape over bedrock rock flour (like sandpaper), make rock flour scrape marks on bedrock: glacial striations give direction of flow Fig. 16.17

12. 4) Glacial landforms & deposits GLACIERS Valleys: Fig. 16.19 glacial trough glacial trough: U-shaped (from V-shaped) hanging valleys hanging valleys: main glaciers cut deeper than side feeds cirques cirques: bowl-shaped depressions at tops of U valleys fiord fiord: steep-sided inlets to sea, drowned glacial troughs

13. 4) Glacial landforms & deposits GLACIERS Valleys: glacial trough glacial trough: U-shaped (from V-shaped) hanging valleys hanging valleys: main glaciers cut deeper than side feeds cirques cirques: bowl-shaped depressions at tops of U valleys fiord fiord: steep-sided inlets to sea

14. 4) Glacial landforms & deposits GLACIERS Arêtes: Sharp-edged ridges Sharp-edged ridges (close cirques, or parallel valleys) Horns: Peaks left over after cirques enlarged

15. 4) Glacial landforms & deposits GLACIERS Aretes: Sharp-edged ridges Sharp-edged ridges (close cirques, or parallel valleys) Horns: Peaks left over after cirques enlarged Matterhorn

16. 4) Glacial landforms & deposits GLACIERS “deposits” Till glacier stratified drift melt water Deposited by  dropped when ice melts  10-100’s m thick  glacial drift - sediments of glacial origin glacial origin

17. 4) Glacial landforms & deposits GLACIERS Till landforms l Moraines end 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

18. 4) Glacial landforms & deposits GLACIERS Till landforms l Drumlins Smooth elongated parallel hills

19. 4) Glacial landforms & deposits GLACIERS Stratified drift landforms l outwash plains l kettle lakes l eskers

20. 4) Glacial landforms & deposits GLACIERS Stratified drift landforms l outwash plains l kettle lakes l eskers

21. 5) Side-effects GLACIERS Ice retreat/advances: some animal/plant migration forced some extinctions Stream flow changes Isostatic rebound Sea level changes Pluvial lakes

22. 5) Side-effects GLACIERS Ice retreat/advances: some animal/plant migration forced some extinctions Stream flow changes Isostatic rebound Sea level changes Pluvial lakes

23. 5) Side-effects GLACIERS Ice retreat/advances: some animal/plant migration forced some extinctions Stream flow changes Isostatic rebound Sea level changes Pluvial lakes See Fig. Story 16.16 + Box. 16.2, p. 371

24. 5) Side-effects GLACIERS Ice retreat/advances: some animal/plant migration forced some extinctions Stream flow changes Isostatic rebound Sea level changes Pluvial lakes If all Earth’s ice melted: ancient Lake Bonneville See Fig. Story 16.16 + Box. 16.2, p. 371

25. 6) Ice ages GLACIERS l Pleistocene: “Ice Age”: Last 1.8 million years 17 cycles of cooling and warming lOlder Ice Ages l Role of Plate tectonics 2.4 billion years ago 750-600 million years ago 250 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 interrupted Fig. 16.29

26. 6) Ice ages GLACIERS l Earth orbit variations Shape of orbit (more elliptical) changes in tilt of rotation axis wobbling 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

27. Other planets! GLACIERS l Other Solar system objects have ice Mars

28. Other planets! GLACIERS l Other Solar system objects have ice Europa (A Jupiter moon)

29. Other planets! GLACIERS

30. MCsGLACIERS How thick are the Greenland and Antarctic ice caps? A. approximately 100 meters thick B. approximately 300 meters thick C. approximately 1 kilometer thick D. approximately 3 kilometers thick

31. MCsGLACIERS Which of the following lists is written in order of increasing ice “metamorphism”? A. snow  granular ice  firn  glacial ice B. snow  firn  glacial ice  granular ice C. snow  firn  granular ice  glacial ice D. snow  granular ice  glacial ice  firn

32. MCsGLACIERS Which of the following erosional features is characteristic of rivers and not glaciers? A. arete B. cirque C. roche moutonée D. V-shaped valley

33. MCsGLACIERS 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

34. MCsGLACIERS Why do glacial crevasses form? A. because glacial meltwater erodes small valleys as glacial rivers flow B. because plate tectonic forces deform the glacier C. because the glacial surface deforms brittlely and cracks as the ice flows D. because the glacial surface partially melts, leaving holes and cracks

35. MCsGLACIERS 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.

36. MCsGLACIERS During the peak of the last ice age, sea level was ______ than sea level today. A. approximately 1 meter lower B. approximately 10 meters lower C. approximately 100 meters lower D. approximately 1000 meters lower

37. MCsGLACIERS When did the last ice age end? A. about 100 years ago B. about 10,000 years ago C. about 1 million years ago D. about 100 million years ago