Chapter 18: Glaciers and Ice Ages

Question 1

sublimate

Answer 1

to evaporate (from snowflake form) directly into vapor

Question 2

firn

Answer 2

deeply buried snow that transforms into a packed granular material

Question 3

glacier

Answer 3

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

Question 4

Mountain Glaciers

Answer 4

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.

Question 5

cirque glaciers

Answer 5

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

Question 6

valley glaciers

Answer 6

rivers of ice that flow down valleys

Question 7

ice caps

Answer 7

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

Question 8

piedmont glaciers

Answer 8

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

Question 9

Continental glaciers

Answer 9

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

Question 10

how do glaciers move?

Answer 10

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)

Question 11

crevasse

Answer 11

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

Question 12

basal sliding

Answer 12

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

Question 13

surge

Answer 13

when a glacier moves faster than normal

Question 14

ablation

Answer 14

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

Question 15

zone of accumulation

Answer 15

where snowfall adds to the glaciers mass

Question 16

equilibrium line

Answer 16

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

Question 17

glacial advance

Answer 17

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)

Question 18

glacial retreat

Answer 18

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)

Question 19

tidewater glaciers

Answer 19

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

Question 20

sea ice

Answer 20

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

Question 21

glacial incorporation

Answer 21

when ice surrounds loose rock and carries it away

Question 22

glacial plucking

Answer 22

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.

Question 23

glacial abrasion

Answer 23

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

Question 24

glacial striations

Answer 24

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

Question 25

tarn

Answer 25

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

Question 26

arete

Answer 26

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

Question 27

V-shaped valley

Answer 27

formed by a river channel

Question 28

U-shaped valley

Answer 28

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

Question 29

hanging valleys

Answer 29

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)

Question 30

truncated spurs

Answer 30

where trunk glaciers remove the ends of ridges between valleys

Question 31

rouche moutonnee; sheep rock

Answer 31

glacially eroded hills

Question 32

fjord

Answer 32

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)

Question 33

moriane

Answer 33

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

Question 34

lateral moraine

Answer 34

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

Question 35

medial moraine

Answer 35

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

Question 36

ground moraine

Answer 36

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

Question 37

end moraine

Answer 37

sediment transported to a glaciers toe and accumulates there

Question 38

glacial drift

Answer 38

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

Question 39

glacial till

Answer 39

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

Question 40

glacial erratics

Answer 40

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

Question 41

glacial marine

Answer 41

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

Question 42

loess

Answer 42

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

Question 43

glacial lake-bed sediment

Answer 43

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

Question 44

varves

Answer 44

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

Question 45

terminal moraine

Answer 45

the end moraine at the farthest limit of glaciation

Question 46

recessional moraine

Answer 46

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

Question 47

drumlins

Answer 47

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

Question 48

kettle holes

Answer 48

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

Question 49

knob and kettle topography

Answer 49

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

Question 50

esker

Answer 50

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

Question 51

glacial outwash plains

Answer 51

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

Question 52

ice-margin lake

Answer 52

meltwater may collect in a lake adjacent to the glaciers toe

Question 53

glacial subsidence

Answer 53

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

Question 54

post glacial rebound

Answer 54

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

Question 55

glacial torrent

Answer 55

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

Question 56

pluvial lakes

Answer 56

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

Question 57

permafrost

Answer 57

permanently frozen ground

Question 58

paleosols

Answer 58

ancient soil preserved in the stratigraphic record

Question 59

glaciation vs. interglaciation

Answer 59

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

Question 60

tillites

Answer 60

ancient glacial deposits that have hardened into rock.