Deck 18: Amazing Ice: Glaciers and Ice Ages

Question 1

Basal sliding of a glacier occurs because of ____________.

A) the steepness of the ground that it flows over
B) the lubricating effects of nonphotosynthesizing algae found beneath some glaciers
C) seeps of methane and other organic gasses or liquids from the underlying sediment or ground
D) water or sediment slurry beneath a glacier

Answer 1

D

Question 2

A boulder that is found in an unlikely place and/or has a different composition than the underlying or nearby rock is possibly a(n)___________.

A) kame
B) erratic
C) arête
D) ventifact

Answer 2

B

Question 3

An intermediate product in the transformation of snow to glacial ice is ____________.

A) firn
B) sublimation
C) ablation
D) terminus

Answer 3

A

Question 4

Which statement about the difference between a piedmont glacier and a continental ice sheet is correct?

A) The toe of a piedmont glacier floats on sea or lake water, whereas that of a continental ice sheet does not.
B) The zone of accumulation of a piedmont glacier is generally at high elevation, whereas that of a continental ice sheet is generally not at high elevation.
C) A piedmont glacier is more likely to cover a vast area, whereas a continental ice sheet is likely to only cover a medium-sized area.
D) Piedmont glaciers are currently found only in the northern hemisphere, whereas continental ice sheets are currently found in both hemispheres.

Question 5

A glacier will advance from its source area if the rate of accumulation is greater than the rate of ____________.

A) subsidence
B) melting
C) ablation
D) abrution

Question 6

The formal definition of an iceberg is ______________.

A) a detached piece of continental ice sheet found floating in open water
B) a free-floating piece of ice at least 15 m long and rising at least 6 m above the water surface
C) a piece of any ice sheet floating in marine water
D) All of the above are correct.

Question 7

Mars has polar ice caps that differ from the Earth's Antarctic ice cap in that ____________.

A) the Martian caps contain some frozen carbon dioxide (dry ice) as well as ice water
B) the Martian caps have a spiral fracture pattern not found in Antarctica
C) Martian caps are ablated by sublimation only; there is currently no liquid water on Mars
D) All of the above are correct.

Question 8

Ice quakes are caused by ____________.

A) the sudden brittle failure of ice when large new crevasses form
B) the manner in which S-waves move through ice
C) surges in the flow of glaciers
D) tectonic uplift beneath large ice sheets

Question 9

Firn consists of ____________.

A) ice crystals with approximately 25% air
B) ice crystals with 20% or less air
C) ice that has been buried deeply enough to flow ductilely, but is now shallow enough to behave brittlely
D) ice with entrained sediment

Question 10

The primary reason that rocks accumulate on the surfaces of glaciers near their toes is ____________.

A) the slope failure (rocksliding, etc.) of nearby cliffs and mountains
B) the incorporation of rock segments from the underlying sediment or rock surface
C) the melting and sublimation of surficial ice downslope from the equilibrium line of a glacier
D) volcanic eruption

Question 11

Near the equator,glaciers only form at elevations greater than ____________.

A) 1 km
B) 2 km
C) 3-4 km
D) 5 km

Question 12

Which location is most likely the site of ablation,A or B?

A) A
B) B
C) They are equally likely.
D) The answer cannot be determined from the information given.

Question 13

The first scientist to theorize the past presence of glaciers in Europe was ____________.

A) Isaac Newton
B) Charles Darwin
C) Walter Alvarez
D) Louis Agassiz

Question 14

Today,continental glaciers are limited to Antarctica and ____________.

A) Alaska
B) Greenland
C) Canada
D) Siberia

Question 15

Glacial ice deforms by ____________ behavior near the top,but ____________ behavior beneath a depth of 60 m.

A) brittle; ductile
B) ductile; brittle
C) solid; liquid
D) plastic; elastic

Question 16

The current interglacial interval began a little more than ____________ years ago.

A) 1,000
B) 10,000
C) 100,000
D) 1 million

Question 17

In the glacier below,approximately how deep is the transition from brittle to ductile deformation?

A) 10 m
B) 60 m
C) 100 m
D) 250 to 300 m

Question 18

Keeping in mind that ice is a mineral,why can a glacier be considered a metamorphic rock?

A) because it is formed by increased pressure and temperature
B) because it is inorganic
C) because it significantly changes in both shape and texture while in the solid state
D) because it is formed by hydrothermal alteration of existing minerals

Question 19

In a glacier,which of the following decreases with increased depth into ice,and/or age of ice?

A) the amount of sediment and rock particles found within it
B) porosity
C) loess content
D) the oxygen-18 (18O) content

Question 20

At the present,glaciers cover about ____________ of the surface of the continents.

A) 1%
B) 5%
C) 10%
D) 20%

Question 21

Because glacial advance is driven by gravity,it is impossible for glaciers to advance over perfectly flat terrain.

Question 22

A universally-applicable term for glacially-derived sediments deposited on land is ____________.

A) drift
B) loess
C) outwash
D) till

Question 23

Sediments deposited directly by glaciers as they melt are characterized by ____________.

A) uniformly coarse grain size
B) uniformly fine grain size
C) an absence of sorting
D) graded bedding

Question 24

Which of the following would NOT be a line of evidence that modern-day geologists could use,to infer the locations and directions of flow of former ice caps?

A) the orientations of striations in bedrock
B) the alignments of drumlins
C) the long axes of U-shaped valleys
D) a comparative study of unsually compositioned clasts in terminal moraines with studies of their source areas

Question 25

Cirques and horns are features associated with ____________.

A) mountain glaciation
B) continental glaciation
C) glacial outwash deposits
D) loess deposits

Question 26

Walking across an Antarctic ice sheet would not be very treacherous if you could stay warm enough.

Question 27

In cross-section,valleys carved by glaciers tend to be shaped like the letter ____________,whereas unglaciated mountain valleys tend to shaped like the letter ____________ in cross-section.

A) V; U
B) V; C
C) U; V
D) V; I

Question 28

The two layers of sediment that are typically deposited each year,in lakes that freeze each winter and melt each summer,are called ____________.

A) varves
B) coupled laminae
C) glacial pairs
D) lacustrine duals

Question 29

A bowl-shaped depression formed by a mountain glacier is termed a(n)____________.

A) arête
B) cirque
C) horn
D) tarn

Question 30

The winds that form loess deposits exist because of ____________.

A) the differences in how land and ice respond to the daily input of solar energy
B) the winds that occur along cold fronts near glaciers
C) the winds that blow from nearby lands onto colder glaciers
D) the high absorbitivity of sunlight by ice

Question 31

Silt-sized particles transported hundreds of km or more and deposited in sometimes thick layers during the ice ages are ____________.

A) firn
B) loess
C) outwash
D) till

Question 32

The figure below shows a conveyor belt as an analogy for a glacier.A,B,and C,respectively,are __________.

A) zone of accumulation; outwash; zone of ablation
B) outwash plain; terminal moraine; zone of accumulation
C) terminal moraine; zone of ablation; zone of accumulation
D) esker; zone of accumulation; zone of deposition

Question 33

A hanging valley exists where a ____________.

A) smaller glacially carved valley intersects a larger, deeper glacially carved valley
B) smaller stream-cut valley intersects a larger stream-cut valley
C) smaller stream-cut valley intersects a larger glacially carved valley
D) stream-cut valley is on the upthrust side of a normal fault

Question 34

A sharp bedrock ridge separating two bowl-shaped depressions formed by mountain glaciers is termed a(n)____________.

A) arête
B) cirque
C) horn
D) tarn

Question 35

The bedrock feature below is most likely a(n)__________.

A) arête
B) kame
C) roche moutonnee
D) lateral moraine

Question 36

A lake that forms within a bowl-shaped depression formed by a mountain glacier is termed a(n)____________.

A) arête
B) cirque
C) horn
D) tarn

Question 37

What is the most accurate statement of the difference between glacial polish and glacial striations?

A) Glacial striations are larger than glacial polish.
B) Striations are caused by rocks and polish is caused by ice.
C) Glacial polish is formed by chemical weathering under wet-bottom glaciers; striations are physical weathering.
D) Polish is caused by the abrasion of sand-size rock clasts; striations are caused by the abrasion of larger sized rock clasts.

Question 38

An angular peak surrounded by three or more bowl-shaped depressions formed by mountain glaciers is termed a(n)____________.

A) arête
B) cirque
C) horn
D) tarn

Question 39

The figure below shows the North Pole/Arctic (left)and South Pole/Antarctica (right).Which of the following is probably NOT a difference between the two?

A) the proportion of dropstones in recent ocean sediments
B) the abundance of icebergs
C) the relative climatological isolation of each from nearby unglaciated landmasses
D) the effects of sea ice versus open water, on the reflection of solar radiation (sunlight)

Question 40

When sea level rises,causing ocean water to fill a glacially carved valley,a ____________ is formed.

A) smorgasbord
B) tarn
C) fjord
D) ford

Question 41

The primary reason that glacial till is rarely bedded is that ____________.

A) waters flowing near glaciers moves chaotically rather than in laminar flow
B) the irregular calving and breakup of glaciers disturbs waters and sediment layers and generally inhibits preservation of bedding that forms in between those events
C) sediment tends not to form beds in cold waters
D) glacial sediment is generally deposited by the melting of ice under and around it

Question 42

Approximately how much has sea level risen since the last ice age ended,approximately 11,000 years ago?

A) 3-4 m
B) 10-20 m
C) 35-40 m
D) 110-120 m

Question 43

The figure below shows the toe of a glacier.What is the gray feature that is between the two heavy black lines?

A) the zone of accumulation
B) an esker
C) a moraine
D) an arete

Question 44

Stratified sorted sand and gravel are deposited by ____________.

A) mountain glaciers
B) continental glaciers
C) glacial outwash streams
D) wind

Question 45

The effect of periodic changes in Earth's orbital eccentricity and magnitude and direction (precession)of Earth's axial tilt on the advance and retreat of ice sheets was first proposed by ____________.

A) Richter
B) Milankovitch
C) Mohorivic
D) Lyell

Question 46

Which of these processes contributes the most to the formation of ice-margin lakes?

A) glacial subsidence
B) erosion of loess
C) moraine retreat
D) glacial rebound

Question 47

The average difference in sea level between ice ages and interglacial periods has been about ____________.

A) 1200 ft
B) 120 m
C) 120 ft
D) 12 ft

Question 48

By increasing the overall reflectance of solar radiation (sunlight),the growth of ice sheets produces conditions that are ____________ to their further advance,thus providing an example of ____________ feedback.

A) detrimental; positive
B) detrimental; negative
C) favorable; positive
D) favorable; negative

Question 49

In the glacier shown below,the diagonally oriented feature at location A is a(n)___________.

A) esker
B) medial moraine
C) crevasse
D) cirque

Question 50

Ice reflects solar radiation (sunlight)very well,whereas water absorbs it.As the Arctic sea ice cover shrinks year after year,what effect will this have on the amount of heat retained in the Arctic?

A) None
B) The amount of heat retained will slowly decrease.
C) The amount of heat retained will slowly increase.
D) There is very little effect, because the steeply angled incoming solar radiation will evaporate seawater, resulting in an extensive cloud cover over the Arctic Ocean.

Question 51

Areas on the southern margins of the continental glaciers of the northern hemisphere were much ____________ during Plio-Pleistocene glaciations than they are today,as suggested by evidence of large ____________ during this time.

A) warmer; tropical rainforests
B) wetter; tropical rainforests
C) drier; deserts
D) wetter; pluvial lakes

Question 52

Which of the following was probably NOT a contributor to the Pleistocene Ice Ages?

A) a long-term cooling trend since the end of the Eocene
B) the closing of the ocean passage between North America and South America
C) the collision of India with Asia and uplift of the Himalayas
D) the burning of wood and plant matter by early humans

Question 53

In the figure below,an ice sheet flows from the upper left to the lower right,where it melts.At which location are you most likely to find a medial moraine?

A) A.
B) B.
C) C.
D) D.

Question 54

The most accurate record of glaciations in the last 2 to 3 million years was ___________.

A) determined from physical and laboratory study of glacial landforms in North America
B) found by coring sediments in Lake Tahoe and other high mountain lakes
C) found by studying plankton skeletons in deep-sea sediment cores
D) found in successive, alternating layers of loess

Question 55

Cape Cod,Massachusetts,and Long Island,New York,are both examples of ____________.

A) drumlins
B) lateral moraines
C) eskers
D) end moraines

Question 56

What will happen to the land surface and lithosphere when the ice sheet melts?

A) It will rise.
B) It will experience volcanism.
C) It will become a rift zone and possibly a divergent boundary.
D) It will subside.

Question 57

Given the modern continental configuration,it is much easier for large continental ice sheets to become established in the ____________ hemisphere than in the ____________ hemisphere.

A) eastern; western
B) western; eastern
C) northern; southern
D) southern; northern

Question 58

Tillites are _____________.

A) sediment layers formed of varves
B) lithified moraines
C) formed in outwash plains
D) rocks formed by lithification of till

Question 59

The primary cause of permafrost is ___________.

A) nightly temperatures of -15°C or colder
B) cold seeping out of glaciers into underlying soil or sediment
C) average temperatures of -5°C or colder
D) the very long winter nights and very short winter days that occur in polar regions

Question 60

An important long-term factor determining whether glacial ice will form on the continents may be the proportion of which gas in the atmosphere?

A) oxygen
B) nitrogen
C) carbon dioxide
D) carbon monoxide