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EAS 225 (Earth Surface/ Landforms) > Midterm Prep > Flashcards

Midterm Prep Flashcards

1
Q

The first known ice age took place in the _____. This is known as the ____ ____

A

archean
snowball earth

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2
Q

the last ice age is referred to as the ____ ____ ___

A

last glacial maximum (LGM)

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3
Q

when did the LGM take place?

A

25-20ka

*ka= 1000s yrs

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4
Q

Generalizations of an ice age:
- ___ global sea level (__m)
- ____ (colder/ warmer) climate
- ecological ____
- extensive ice sheets to ___-___
- ____ glaciation

A

lower (120m)

colder

changes

mid-latitudes

periodic

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5
Q

Explain the origins of “ice age” theory. Who led most of this?

A

Early scientists were confused by poorly sorted sediments and boulders. The controversial ideas that glaciers once covered Europe and N. America arose.
This was led by Louis Agassiz

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6
Q

T/F
By the 19th century, the idea of extensive past glaciation was more accepted

A

true

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7
Q

Once ideas of past glaciation were more accepted, what did the focus shift to? What was the consensus?

A

focus was shifted to # of glacial events. The consensus was 4 glacial events in N. America and Europe

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8
Q

What is “Etudes sur les glaciers”?

A

“A study on Glaciers”
A book by Louis Agassiz, principle of uniformitarianism introduced

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9
Q

What is Astronomical Theory? What is it often known as?

A

ie Milankovitch theory

Idea that Earth’s orbit around the sun is not constant, and that these changes in orbit lead to spatial and temporal difference in distribution of energy at Earth’s surface

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10
Q

The 3 aspects of Milankovitch theory are:
1
2
3

A
  1. Eccentricity (shape of orbit)
  2. Obliquity (tilt)
  3. Precession (wobble)
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11
Q

Paleoceanography=

A

the study of the oceans as they were in the past, from a few hundred years to billions of years ago, with the aim to reconstruct their physical, chemical and biological character

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12
Q

T/F
stable isotopes decay

A

false!

stable isotopes do NOT decay

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13
Q

Physical, chemical, and biological transformations lead to changes (ie. ______) in the relative abundance of _____

A

fractionation

isotopes

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14
Q

Which is more likely to evaporate, water with 16O or water with 18O? Condense?

A

Water with 16O is more likely to evaporate than water with 18O (because it’s lighter)

Water with 18O is more likely to condense than water with 16O

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15
Q

______ secrete at CaCO3 “test” shell

A

foraminifera

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16
Q

What is a glacier?

A

= a body of ice that flows under the influence of gravity and its own mass

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17
Q

What are 2 examples of ice movement that could classify it as a glacier?

A

Deformation of ice, sliding (*under the influence of gravity and its own mass)

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18
Q

Glaciers will form when ice accumulation is ____ (less/ greater) than ice loss. What is this called?

A

Glaciers will form when ice accumulation is GREATER than ice loss.
= Accumulation

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19
Q

T/F
Studying glaciers can be useful, but can’t give us a baseline for future climate changes

A

False
They can preserve highly resolved records of past environments that provide a baseline for future changes (temp, dust, pollution,
volcanism)

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20
Q

T/F
glaciers and ice sheets interact strongly with the climate system through a variety of feedbacks

A

true

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21
Q

Is it possible to find evidence of glaciers across the northern hemisphere?

A

Yes!
Surface sediments associated with growth and decay of ice sheets are widespread across the N. hemisphere

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22
Q

List some things that are factors of the distribution of glaciers

A

elevation, aspect/ topography, continentality, marine currents, ocean temps

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23
Q

T/F
avalanches, calving, sublimation, and geothermal heat flux don’t have much impact on the distribution of glaciers because they’re relatively small-scale

A

FALSE
these all play a role in shaping the distribution of glaciers

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24
Q

mass balance=

A

net difference between accumulation and ablation over time (usually winter/ summer cycle)

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25
Q

Glaciers will recede when ice accumulation is ____ (less/ greater) than ice loss. What is this called?

A

LESS
= ablation

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26
Q

what is the density of snow?

A

= 0.05g/cm^3

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27
Q

Explain what firnification is.
What’s the density of firn?

A

= a process when snow survives a year of summer melt to become firn
Density of firn ~ 0.8g/cm^3 (void space reduced)

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28
Q

The density of glacial ice is ___g/cm^3 (____ dense than snow and firn)

Are there any void spaces? Is there exchange with the atmosphere?

A

0.9g/cm3

MORE

All void spaces are isolated. There is no exchange with the atmosphere

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29
Q

Thermal regime determines:

A

determines how material is eroded and transported, glacier velocity, and geomorphic legacy of glaciations (landforms)

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30
Q

Cold-based glacier=

A

frozen to bed, no subglacial water

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31
Q

warm-based glacier=

A

Basal ice is at high pressure, so above melting point. This results in the presence of liquid water at the base of the glacier

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32
Q

Polythermal ice=

A

cold/ warm based in different places and times

33
Q

A body of ice is greater than 50,000km^2. What is it classified as?

A

An Ice sheet

34
Q

A body of ice is less than 50,000km^2. What is it classified as?

A

An ice cap

35
Q

Icefields=

A

the glacier fills and elevated basin (controlled by topography), commonly with radiating outlet valley glaciers

36
Q

Cirque glacier=

A

occupies a small basin on a mountain slope

37
Q

Piedmont glacier=

A

lobe-shaped glacier formed when steeper ice spills out into a broad lowland

38
Q

Tidewater Glacier=

A

a glacier that terminates at sea level into the ocean

39
Q

Calving=

A

ablation of glacier ice by breaking off into the ocean

40
Q

There is only one movement mechanism possible for cold-based glaciers. What is this motion called? Describe it

A

= internal deformation (“creep”): change in shape of ice crystals in response to an applied load (strain)

41
Q

Basal sliding is a type of glacier motion, explain how it works

A

basal sliding= sliding along the interface between ice and substrate
- strongly controlled by presence of water, whereby glacier can be locally detached from its bed

42
Q

What is subglacial deformation? What largely controls it?

A

= deforming of sediments underlying base of ice, which contributes to the overlying glacier

  • strongly controlled by presence of water and nature of underlying materials
43
Q

Why do crevasses form?

A

They form when ice can’t deform fast enough to an applied stress, resulting in brittle failure

44
Q

T/F
internal deformation heals surface fractures where crevasses form

A

true

45
Q

What is a glacier surge?

A

transient episode of rapid movement 10-100x the normal velocity of the glacier
- Lead to a rapid transfer of mass from high to low elevation

46
Q

T/F
glacier surges are directly related to climate

A

false
glacier surges are internally driven, not directly related to climate

47
Q

How long do glacier surges last?

A

Can last for months up to ~1yr, separated by many years of quiescence

48
Q

Looped moraines=

A

moraines from tributary glaciers that get stretched out by the surging glacier

49
Q

Surge-front propogation:

A

indicates buildup of ice reservoir, which will eventually be rapidly transferred downslope during a surge

50
Q

What can happen if there’s lots of water at the base to facilitate basal sliding?

A

= high basal water pressure!
This can locally approach ice overburden pressure

51
Q

Till=

A

a generic term for unsorted, generally unstratified sediment, directly deposited by a glacier

52
Q

What are the 3 principles for till-formation?

A
  1. Lodgement
  2. Deformation
  3. Melt-out
53
Q

Describe “lodgement” in the till-formation process

A

= the plastering of debris along the base of moving ice
- occurs when frictional resistance exceeds the shear stress at the base of the ice

54
Q

Describe “deformation” in the till-formation process

A

= change in the shape and orientation of sediments

55
Q

Subglacial sediment deformation will occur when:
1
2

A
  1. the glacier is coupled to the underlying sediment
  2. shear stress from overlying ice exceeds the shear strength of the underlying sediment
56
Q

Describe “melt-out” in the till-formation process

A

= the slow release of sediment from basal ice due to melting

57
Q

Debris-rich ice will be deposited during melting at the ___ of the glacier

A

base

58
Q

Subglacial erosion=

A

processes occurring at interface between ice and ground surface that promote the breakdown of surface materials.
There are 2 main processes

59
Q

What are the 2 main processes of subglacial erosion?

A
  1. Abrasion= wearing down of bedrock by direct contact b/w particles carried by ice and the surface
  2. Plucking/ Quarrying= fracture due to stress build-up leads to detachment of rock fragments that are then entrained (carried away)
60
Q

What are 2 landforms associated with erosion by abrasion?

A
  1. Striation
  2. Glacier polish
61
Q

Striation=

A

particles carried by ice directly abrade thin linear grooves into bedrock or clasts. Appear smooth, but are the result of a series of microfractures due to a build-up of stress

62
Q

Glacier Polish=

A

polishing of bedrock surfaces by action of smaller particles (carried by ice) being dragged across the bedrock

63
Q

Landforms associated with erosion by plucking are called:

A

Roche Moutonee
(rock looking like a sheep at rest)

64
Q

Aretes, horns, U-shaped valleys, and hanging valleys are all landforms associated with ____

A

erosion

65
Q

Arete=

A

A ridge that forms between cirques

66
Q

Horns=

A

erosional remnant of glacier erosion (high triangular peak)

67
Q

U-shaped valleys=

A

longitudinal valleys produced by widening & deepening of pre-existing valleys by glacial erosion

68
Q

Hanging valley=

A

a tributary valley that enters a larger U-shaped valley

69
Q

Equifinality=

A

principle that in open systems a given end state can be reached by many potential means

70
Q

Drumlins=

A

glacially elongated hills, generally w/ steep stoss side and gently sloping lee side

teardrop shape in planform

71
Q

Flutings are __glacial ____. Describe what they might look like

A

Like drumlins, but stretched, and lacking teardrop planform and “inverted spoon” cross-section.
- Parallel ridges, tens of cm to a few m high and wide, & tens of m in length

72
Q

Moraines=

A

ridges or mounds of glacial material deposited at, or close to, ice margins

73
Q

Hummocky moraine=

A

topographically, a strongly undulating surface of irregular, steep, small hills and hollows

74
Q

Gilbert Deltas provide evidence of past ___ level

A

water

75
Q

dropstones=

A

clasts carried by floating ice & released as ice melts

76
Q

varves=

A

annual couplet of fine sediment recording seasonal changes in deposition

77
Q

___ __ ___ developed the study of varves for glacial geochronology

A

Gerald de Geer

78
Q

What does the term “palimpsest” mean?

A

refers to something reused or altered but still bearing visible traces of its earlier form

79
Q
A

EAS 225 (Earth Surface/ Landforms) (13 decks)

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