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Intro to Geology > Chapter 18: Glaciers and Ice Ages > Flashcards

Chapter 18: Glaciers and Ice Ages Flashcards

1
Q

sublimate

A

to evaporate (from snowflake form) directly into vapor

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2
Q

firn

A

deeply buried snow that transforms into a packed granular material

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3
Q

glacier

A

a stream or sheet of recrystallized ice that stays mostly frozen all year long and flows under the influence of gravity.

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4
Q

Mountain Glaciers

A

aka alpine glaciers; exist in or adjacent to mountainous regions if temperatures remain cold enough. Flow from higher elevations to lower elevations. Include cirques, valley glaciers, ice caps, and piedmont glaciers.

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5
Q

cirque glaciers

A

fill bowl-shaped depressions (cirques) on the flank of a mountain

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6
Q

valley glaciers

A

rivers of ice that flow down valleys

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7
Q

ice caps

A

mounds of ice that submerge peaks and ridges at the crest of a mountain range

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8
Q

piedmont glaciers

A

fans or lobes of ice that form where a valley glacier emerges from a valley and spreads out in to the adjacent plain.

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9
Q

Continental glaciers

A

vast ice sheets that spread over thousands os square kilometers of continental crust. Today these only exist in Antarctica and Greenland, and rest mostly on solid ground

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10
Q

how do glaciers move?

A

through plastic deformation (the process where existing grains of ice slowly change shape without breaking or new grains grow while old ones disappear); this occurs at the deeper part of the glacier (below the brittle plastic transition depth)

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11
Q

crevasse

A

a crack that opens into a downward tapering gash (occurs higher in the glacier; above the brittle plastic transition)

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12
Q

basal sliding

A

when a glacier glides along on a wet sediment slurry without coming into frictinal contact with bedrock and as a consequence, may undergo a surge

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13
Q

surge

A

when a glacier moves faster than normal

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14
Q

ablation

A

the removal of ice by melting, sublimation (vaporizing directly), and calving (breaking off chunks)

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15
Q

zone of accumulation

A

where snowfall adds to the glaciers mass

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16
Q

equilibrium line

A

the boundary between the zone of ablation and the zone of accumulation

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17
Q

glacial advance

A

when the rate at which ice builds up in the zone of accumulation exceeds the rate at which ablation occurs, then the glacial toe move forward into previously unglaciated regions (position of the toe move downslope in this case)

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18
Q

glacial retreat

A

when the rate at which ablation occurs exceeds the rate at which ice builds up in the zone of accumulation (toe moves back toward the origin of the glacier)

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19
Q

tidewater glaciers

A

glaciers whose toes lie in the sea water; valley glaciers entering the sea become ice tongues (longer than they are wide); continental glaciers entering the sea are known as ice shelves

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20
Q

sea ice

A

occurs where the surface of the sea itself freezes; not technically glacial ice

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21
Q

glacial incorporation

A

when ice surrounds loose rock and carries it away

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22
Q

glacial plucking

A

occurs when ice flows into joints that intersect the bedrocks surface. Freezing and thawing, along with the push of moving ice, causes joints to grow until a joint-bounded block of rock finally breaks free of its substrate and starts to move with the ice.

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23
Q

glacial abrasion

A

as glaciers flow, sand and silt embedded in the ice act like the teeth of a giant rasp and grind away the substrate

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24
Q

glacial striations

A

where clasts moving with the glacial ice carved grooves or scratches into bedrock

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25
Q

tarn

A

a lake formed at the point where the head (source of a glacier) once existed

26
Q

arete

A

a residual knife-edge ridge of rock, separates two adjacent cirques

27
Q

V-shaped valley

A

formed by a river channel

28
Q

U-shaped valley

A

forms because the combined processes of glacial abrasion and plucking not only lower the floor of the valley, but also erode its sides.

29
Q

hanging valleys

A

where a glacier cuts the floor of its valley down to a depth that far exceeds the depth cut by the tributary glaciers. consequently, when the glaciers melt away, the mouths of the tributary valleys perch at a higher elevation than the floor of the trunk valleys (waterfalls)

30
Q

truncated spurs

A

where trunk glaciers remove the ends of ridges between valleys

31
Q

rouche moutonnee; sheep rock

A

glacially eroded hills

32
Q

fjord

A

a glacially carved valley that has filled with water; occur in Norway, New Zealand, Chile, Alaska, and Greenland

  • marine fjords/coastal fjords (occur along the coast and fill with seawater)
  • freshwater fjords (inland lakes)
33
Q

moriane

A

a pile of sediment either carried on or left behind by a glacier

34
Q

lateral moraine

A

sediment dropped on the side margins of a glacier (bathtub rings)

35
Q

medial moraine

A

a stripe down the interior of the composite glacier (where two valley glaciers might come together, their meet would form this type of moraine

36
Q

ground moraine

A

sediment left at the base of the glacier when it melts away

37
Q

end moraine

A

sediment transported to a glaciers toe and accumulates there

38
Q

glacial drift

A

the several different types of sediment that can be deposited in glacial environments. Includes:

  • glacial till
  • glacial erratics
  • glacial marine
  • glacial outwash
  • loess
  • glacial lake-bed sediment
39
Q

glacial till

A

sediment transported by ice and deposited beneath, at the side, or at the toe of a glacier moraine; not sorted

40
Q

glacial erratics

A

relatively large cobbles and boulders that have been dropped by a glacier, can be in till or on a glacially polished surface

41
Q

glacial marine

A

clasts carried out to sea by icebergs, when the ice melts the clasts sink to the sea floor

42
Q

loess

A

forms from clay and silt that were transported by strong katabatic winds

43
Q

glacial lake-bed sediment

A

fine grained sediment, including rock flour, that accumulates on the floor of a meltwater lake; contains varves

44
Q

varves

A

a pair of thin layers deposited during a single year; one layer of silt brought in with spring floods, and a clay layer deposited in winter when the lakes surface freezes over and water is still

45
Q

terminal moraine

A

the end moraine at the farthest limit of glaciation

46
Q

recessional moraine

A

an end moraine that forms when a glacier stalls temporarily while receding

47
Q

drumlins

A

from the Gaelic word for small hill or ridge, flowing glacial ice reshapes the underlying till into elongate hills

48
Q

kettle holes

A

form when till covered blocks of ice calve off the toe of a glacier; when the blocks melt, the depressions form

49
Q

knob and kettle topography

A

land surfaces spotted with many kettle holes separated by rounded hills or ridges of sediment

50
Q

esker

A

sediment deposited in meltwater tunnels beneath a glacier as a sinuous ridge after the glacier has melted away

51
Q

glacial outwash plains

A

braided meltwater streams that flow beyond the end of a glacier deposit layers of sand and gravel

52
Q

ice-margin lake

A

meltwater may collect in a lake adjacent to the glaciers toe

53
Q

glacial subsidence

A

when a large ice sheet grows on a continent, its weight causes the surface of the lithosphere to sink

54
Q

post glacial rebound

A

when a large ice sheet melts, gradually, the surface of the underlying continental lithosphere rises back up

55
Q

glacial torrent

A

erosion caused by glaciers that results in an ice dam or moraine dam suddenly breaking, yielding an immense flood

56
Q

pluvial lakes

A

lakes that accumulated to the south of continental ice sheets due to enhance rainfall

57
Q

permafrost

A

permanently frozen ground

58
Q

paleosols

A

ancient soil preserved in the stratigraphic record

59
Q

glaciation vs. interglaciation

A

glaciation: an ice age
interglaciation: the time between an ice age

60
Q

tillites

A

ancient glacial deposits that have hardened into rock.

Intro to Geology (14 decks)

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