1. GLACIERS
A LARGE MASS OF ICE ON LAND THAT FLOWS UNDER THE PRESSURE OF ITS OWN WEIGHT – DOWNHILL OR OUTWARD DUE TO GRAVITY

2. Glaciers: 2 Types
ALPINE(VALLEY) GLACIERS: long, slow-moving, streams of ice found in mountain areas (high elevation) occupying former river valleys
CONTINENTAL GLACIERS (ICE SHEETS): very old (1000’s of years), thick (1000’s of meters) mass of ice covering almost an entire land mass
GREENLAND: 1.7 Million SQ MI , 3 KM thick
ANTARCTIC: 12.5 Million SQ MI, 5 KM thick

3. GLACIERS - VALLEY AND CONTINENTAL

4. CONTINENTAL ICE SHEETS

5. WHERE DO THEY FORM?
AREAS OF HIGH LATITUDE OR HIGH ELEVATION WHERE THEY HAVE COLD SUMMERS
PRESENTLY OCCUPY 10% OF WORLD’S TOTAL LAND AREA
(COMPARED TO 32% DURING THE PLEISTOCENE EPOCH)

7. HOW DO THEY FORM? MORE SNOW MUST FALL THAN MELTS
ZONE OF ACCUMULATION – SNOW TURNS TO ICE AT UPPER PART OF GLACIER
ZONE OF MELTING (ABLATION) – LOWER PART
SNOW LINE (EQUILIBRIUM LINE) LINE WHERE SNOW IS ALL YEAR LONG

8. Process of Glacier Formation
SNOWFLAKES ACCUMULATE
SNOWFLAKES COMPACT
FIRST INTO FIRN (LIKE PACKED SNOWBALLS)
LOWER LAYERS TURN INTO GLACIAL ICE (SOLID ICE – NO AIR) UNDER THE WEIGHT OF OVERLYING FIRN AND SNOW

9. Firn Firn is an intermediate stage between snow and glacial ice
When more snow is accumulated than is melted, the snow clumps together and will ultimately become glacial ice

11. HOW DO GLACIERS MOVE? UNDER THE INFLUENCE OF GRAVITY
THEIR OWN WEIGHT IS THE DRIVING FORCE
UNDER PRESSURE THE DEEPER ICE BEHAVES LIKE A THICK FLUID (CALLED PLASTIC FLOW) AND FLOWS DOWNHILL OR SPREADS OUT IN ALL DIRECTIONS
(when glacier is about 300 ft. thick)

12. GLACIER MOVEMENT GLACIER ADVANCES SNOWFALL > MELTING
GLACIER RETREATS SNOWFALL < MELTING
STATIONARY GLACIER SNOWFALL = MELTING DYNAMIC EQUILIBRIUM

13. ICE WITHIN GLACIER IS ALWAYS MOVING FORWARD EVEN IF THE GLACIER IS RETREATING OR STATIONARY
MANY DEPOSITIONAL FEATURES ARE FORMED AS A RESULT

14. GLACIER FLOW
SPEED IS LIKE A STREAM – FASTER IN THE MIDDLE / LESS FRICTION
fastest movement after 1) heavy winters, 2) steep slopes, and 3) in summer
WHY???
CREVASSES form along steep slopes because upper zone of glacier is rigid (rarely go deeper than 120ft. )

15. FASTEST

16. A CREVASSE- Evidence of movement

17. HOW DO GLACIERS ERODE?
Most powerful erosional agent because of their great size and weight
Glaciers erode by:
Abrasion – wearing, grinding, scraping rock surface because rock fragments are frozen into the ice at the bottom (ROCK FLOUR)
Plucking – rock fragments loosened, picked up and carried by glaciers

19. EROSIONAL FEATURES
Striations - Grooves carved into the bedrock by pebbles and cobbles carried at the bottom of a glacier – can show direction of glacial movement
Polished Bedrock
Sediment - TILL - is angular and NOT SORTED AND NOT LAYERED

22. Unsorted Materials- all sizes mixed together.

23. Glacial Polish Smooth rock surfaces created as glaciers flow over bedrock.

24. Glacial Pavement….

25. ERRATIC – EVIDENCE OF GLACIER EROSION
A boulder-sized rock dumped by a glacier. The rock is usually of a different type than the surrounding rock…

30. VALLEY GLACIERS

31. VALLEY GLACIER EROSIONAL FEATURES
Mountain ranges that were scenic to begin with are now jagged, angular peaks
GLACIERS MODIFY RIVER VALLEYS BY…
TURNING THE V-SHAPE RIVER VALLEYS INTO
U-SHAPED GLACIATED VALLEYS

32. EROSIONAL LANDSCAPE FEATURES OF VALLEY GLACIERS
CIRQUES: semi-circular shaped bowl created as a glacier scours back toward the mountain (1st place snow and ice accumulate)
ARÊTES: steep-sided, sharp-edged bedrock ridge formed by two glaciers eroding away on opposite sides of ridges
HORNS: 3 or more cirques adjacent to one another
TARNS: glacial lakes produced by glacial scouring- often found in cirques
HANGING VALLEYS: valley eroded by a small tributary glacier; floor is at a higher elevation that valley it feeds into…

35. HORN
HANGING VALLEY

36. ARÊTE
CIRQUE

37. CIRQUE
TARN

38. ARÊTE
CIRQUE
HANGING VALLEY
U-SHAPED VALLEY

41. VALLEY GLACIER DEPOSITIONAL FEATURES
MORAINES – unsorted, un-layered pile of till
UNSORTED IS THE KEY WORD!!!!
There are many types of moraines
Lateral – till along side of glacier
Medial – 2 glaciers come together and the lateral moraines join in a single ridge
Terminal or End – farthest advance of glacier
Recessional – glacier retreats, pauses, deposits – will be parallel to terminal moraine

43. Juneau, Alaska

44. f05_07a_pg84
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45. CONTINENTAL GLACIERS

46. CONTINENTAL OR ICE SHEET GLACIERS
MOST FLOW OVER RELATIVELY FLAT AREAS SO LANDSCAPE FEATURES ARE LESS DRAMATIC – ROUNDED HILLS (valley glaciers sharpen and continental glaciers round)
LAKES AND SWAMPS
GREAT LAKES
FINGER LAKES

49. The Finger Lakes consist of 11 long, narrow, roughly parallel lakes, oriented north-south as fingers of a pair of outstretched hands. The southern ends have high walls, cut by steep gorges.

50. CONTINENTAL GLACIER DEPOSITIONAL FEATURES
MORAINES – glacially formed accumulation of debris
DRUMLINS - ground moraine that is mounded into a stream-lined oval shape hill (inverted spoon) – steep side points in direction the glacier came from
KETTLE LAKES – large, buried ice blocks melted and left depressions Ex. Lake Ronkonkoma
OUTWASH PLAIN - deposits made by streams after glaciers melt (sorted/stratified)

51. Kettle Lake Drumlins Outwash plain Till Glacial Stream
Esker
Outwash plain
Till
Moraine-dammed lake
Glacial Stream
Terminal Moraine

54. DRUMLIN

55. DRUMLINS