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Geomorphology > Ice Age > Flashcards

Ice Age Flashcards

1
Q

what is an ice age

A

period of long term reduction in temp of the earth’s surface

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2
Q

what do ice ages result in

A

the presence or expansion of continental and polar ice sheets and alpine glaciers

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3
Q

what type of glaciers are present in an ice age

A
  1. continental ice sheet
  2. polar ice sheets
  3. alpine glaciers
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4
Q

describe the phases in a long term ice age

A

glacial period - period of cold climate where ice expands

interglacial period - intermittent warm periods between glacial phases where ice retreats and temps warm

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5
Q

how does the definition change in glaciology

A

implies the presence of extensive ice sheets in both NORTHERN and SOUTHERN hemispheres

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6
Q

are we currently in an interglacial or glacial period

A

interglacial period

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7
Q

what is the name of the interglacial period we are in

A

Holocene

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8
Q

when did the Holocene start

A

about 0.1 million years ago

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9
Q

when was the most recent ice age

A

started about 2.6 million years ago

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10
Q

what epoch did the most recent ice age start at

A

Pleistocene epoch

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11
Q

did an interglacial or glacial period start in the Pleistocene epoch

A

glacial period

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12
Q

how many large ice age periods have happened in the last 5 million years

A

4

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13
Q

how many periods of glaciation have happened in the last 450 000 years

A

4

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14
Q

glaciation

A

single episode or time period where ice sheets formed spread and disappeared

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15
Q

when does glaciation end

A

when the ice disappears

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16
Q

when do glaciation events occur

A

when temps drop or snowfall increases

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17
Q

describe what earth looked like 55 million years ago

A

there was lack of ice on the continents which led to higher sea levels because no water was trapped in terrestrial glaciers

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18
Q

describe the earth 5 million years ago

A

ice caps began to form in the north and south extremes (poles)

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19
Q

describe what earth looked like in most recent ice ages

A

larger ice sheets were found at Northward because there was more land there compared to down south (which had smaller ice sheets)

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20
Q

what is the glacial theory proposed by Louis Agassiz

A

glaciers had been much larger and more widespread in the last few million years with FOUR major glacial stages recognized in NA

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21
Q

what are the four glacial stages in NA according to Agassiz

A
  1. Nebraskan
  2. Kansan
  3. Illinoian
  4. Wisconsinan
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22
Q

how much of earth’s surface was covered by ice according to Agassiz

A

30%

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23
Q

what was the youngest (most recent) glacial stage in NA

A

Wisconsinan

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24
Q

what was the oldest glacial stage in NA

A

Nebraskan

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25
Q

order the major glacial stages in NA from oldest to youngest

A
  1. Nebraskan
  2. Kansan
  3. Illinoian
  4. Wisconsinan
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26
Q

what major glacial period is this in NA

A

Wisconsinan

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27
Q

what major glacial period is this in NA

A

Illinoian

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28
Q

what major glacial period is this in NA

A

Kansan

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29
Q

what major glacial period is this in NA

A

Pre Nebraskan

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30
Q

of the four major glacial periods in NA which is talked about most and why

A

Wisconsinan - most recent which means any other glaciation events that happen after have not had a chance to remove and destroy any sediments that would destroy the record of the glacial period

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31
Q

what is the Late-Cenozoic ice age

A

series of glaciation, deglaciation and interglaciations experienced during the late Cenozoic era

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32
Q

how do we relate to the Late Cenozoic Era

A

its the time period (era) we are technically in

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33
Q

how do scientists have evidence for past ice ages

A
  1. sediment cores from the ocean floor and ice cores
  2. evidence of magnetic reversals in the ocean
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34
Q

how far back do deep sea cores show alternating glaciations and interglaciations

A

back 2 to 3 million years

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35
Q

how do deep ocean floor cores reveal information about past glaciation events

A

looking at the oxygen isotopes show the ratio of heavy to light water where more heavy water in the ocean= more light water on land = ice sheets on land

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36
Q

what are magnetic reversals

A

the process by which the North pole is transformed into a South pole and the South pole becomes a North pole

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37
Q

what are some possible causes of ice ages

A
  1. motion of tectonic plates and uplift of Tibetan plateau
  2. volcanic activity that blocks solar radiation
  3. decrease in sun energy output
  4. change in atmospheric conditions (reduce green house gases)
  5. changes in ocean currents
  6. variations in earth’s orbit
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38
Q

what is the Tibetan plateau and its significance

A

the largest area of uplifted crust on Earth which holds largest ice mass besides poles and if it moves to higher altitudes = more formation of glaciers

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39
Q

how does changing atmospheric composition affect glaciation

A

changing atmospheric conditions changes the behaviour of weather and climate

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40
Q

when do ice ages start

A

when continents are in positions that block or reduce warm water flow from equator to the poles

41
Q

how does ice affect albedo

A

earth having more ice on its surface increases albedo which reduces the absorption of solar radiation = cools atmosphere and increases ice growth

42
Q

what eventually impedes the growth of ice sheets

A

when reducing in weathering causes an increase in greenhouse gases which warm the atmosphere and lowers albedo

43
Q

what formation of continents most promotes the formation of ice

A
  1. being in higher altitudes
  2. forming a large land mass that disrupts the ocean currents
44
Q

does volcanism contribute to the start or ending of ice age periods

A

BOTH

45
Q

how does volcanism contribute to start of ice ages

A

when huge volcanoes erupt and release large clouds of ash that prevent solar radiation from penetrating down to earth which starts an ice age

46
Q

how does volcanism contribute to ending of ice ages

A

when volcanoes erupt CO2 is released into the atmosphere which is a GHG = increases the atmosphere temp = warms earth and stops ice age

47
Q

what is responsible for some of the highest temps ever seen on earth

A

volcanism

48
Q

what are a suggested explanation for the paleocene-eocene thermal maximum

A

sudden release of methane hydrates from ocean sediments triggered by a massive volcanic eruption

49
Q

describe how the level of greenhouse gases changed at the start of ice age and end of ice age

A
  1. at the start of ice age the level FELL
  2. at the retreat of ice sheets (end of ice age) the level ROSE
50
Q

what are some factors that affect greenhouse gas levels

A
  • volcanism
  • plate tectonics
51
Q

what is the snowball earth hypothesis

A

Earth’s oceans and land surfaces were COMPLETELY covered by ice from the poles to the Equator

52
Q

how was the snowball earth theory proposed to end

A

severe freezing in the LATE PROTEROZIC was ended by increases CO2 levels in atmosphere due to volcanoes

52
Q

describe the 5 stages of the snowball earth theory

A
  1. an extended cold spell the oceans started to freeze and polar ice caps began to enlarge
  2. the lower reflectivity caused by increasing ice sheets caused further cooling
  3. the CO2 cycle in oceans stops and CO2 released by volcanoes builds up in atmosphere because it cannot be removed into ocean sink
  4. the large accumulation of CO2 in atmosphere warms the earth and melts the snowball earth
  5. CO2 cycle restarts which pulls CO2 back into the oceans and reduces GH effect to normal
53
Q

what are examples of factors that affect climate

A
  1. continent location
  2. sea level s
  3. salinity of oceans
54
Q

how do ocean current fluctuations cause ice ages

A

the cool water of the Labrador current is being pushed more northward by the Gulf current which is causing further lowering of water temps and increase of ice sheet formation

55
Q

importance of ocean currents

A

Ocean currents drive global ocean circulation, redistributing heat from the equator to the poles = warming pole water and preventing over formation of ice sheets

56
Q

what happens if Gulf stream current stop

A

it could lower temperatures by up to 10 or 15 degrees in Europe and lead to rising sea levels in the eastern US = ushering in ice age

57
Q

what is the astronomical hypothesis

A

explanation for glaciations and interglaciations based on cyclic variations in solar energy received at earth’s surface

58
Q

what is the current angle of earth’s wobble

A

23.5 degrees

59
Q

how would one degree more OR less of earth’s axis wobble result in

A

MORE
- greater seasonal differences on earth

LESS
- less seasonal differences in North and South hemispheres

60
Q

what is the typical variation between earth’s axis

A

22.1 to 24.5 degrees

61
Q

how long is cycle of earth’s axis changes (Obliquity)

A

41 000 years

62
Q

obliquity refers to

A

earth’s change in axis angle

63
Q

precession refers to

A

earth’s axis wobble (equinoxes)

64
Q

eccentricity refers to

A

the shape of earth’s orbit

65
Q

describe the shape of earth’s orbit

A

more OBLONGED/ELLIPTICAL than spherical

66
Q

how long is cycle of earth’s axis wobble (precession)

A

26 000 years

67
Q

how long is cycle of earth’s orbit (eccentricity)

A

100 000 years

68
Q

what happens when all three variations of earth’s orbit combine

A

results in minimum solar energy and surface temps which initiates glaciation events

69
Q

what is the Holocene epoch

A

the last epoch of geologic time

70
Q

when did the holocene epoch start

A

about 10 000 years ago (end of last ice age) and is continuing into the present

71
Q

three main climate periods in Holocene

A
  1. Boreal stage
  2. Atlantic stage
  3. Subboreal stage
72
Q

describe the three major climate periods in Holocene

A

Boreal
- boreal forest vegetation growth begins to be seen in midlatitude regions

Atlantic
- warmer temps which started about 8000 years ago and relates to START OF AG

Subboreal stage
- cooler stage about 5000 years ago to 2000 years ago relating to global expansion of AG

73
Q

what is the warmer major climate period in Holocene

A

Atlantic stage

74
Q

what is the colder major climate period in Holocene

A

Subboreal stage

75
Q

describe the past 2000 years in Holocene

A
  1. it was warm from 1000 AD to 1200 AD
  2. there was a small drop in temp (little ice age) from 1450 AD to 1850 AD
  3. there is a global increase in temp at present relating to industrial revolution
76
Q

what are some indirect effects of ice age glaciers

A
  1. forced migration of animals and plants (joining of continents allowed organisms to reach locations not able to reach otherwise)
  2. changes in stream courses
  3. isostatic rebound of continents
  4. changes in global sea levels (based on how water is being taken out of oceans in glacial period and added in interglacial period)
  5. glacial lakes
  6. aeolian dust deposits (loess which was good for farming)
77
Q

what was the largest glacial lake

A

Agassiz

78
Q

importance of glacial lake Agassiz

A

responsible for creation of Great Lakes

79
Q

what are the three main types of evidence for ice ages

A
  1. chemical
    - ocean cores
    - ice cores
    - marine organisms
  2. geological
  3. paleontological
    - pollen samples,
    - organism dating
    - flora data
80
Q

describe geological evidence for ice age

A
  • glacial erosion
    (ex. polishing and striations)
  • glacial deposition
    ( ex. moraines, drumlins, tills, erratic)
81
Q

what is an issue with successive glaciations

A

tend to distort and erase the geological evidence of past glaciation events

82
Q

why is geological evidence for ice ages hard to date

A

because most of it is sedimentary which has been carried from its in situ place by glaciers - so it was not originally part of it and dating correlates to dating the ROCK and NOT the glacier ice

83
Q

describe chemical evidence for ice ages

A
  • variations in ratios of isotopes in fossils found in sediments and ice cores
84
Q

describe paleontological evidence for ice ages

A
  • the global distribution of fossils showing migration of non native species
85
Q

where are organisms usually found in glacial periods

A

lower latitudes

86
Q

how does glacial periods affect organisms adapted to WARMER weather

A

they either go extinct OR they get forced in to very narrow habitat with warm temps at lower latitudes

89
Q

what is the most recent and BEST KNOWN ice age

A

Late Cenozoic ice age

89
Q

how long was the Late Cenozoic ice age

A

34 mya to present

89
Q

what evidence is there for the Late Cenozoic ice age

A

1, rock fragments in sediments of southern oceans dropped by ice bergs

2, layers of glacial deposited rock debris under lava flows dated to 10 mya

90
Q

how thick was the Late Cenozoic ice age ice

A

over 3 km thick

91
Q

how much of the planet was covered by the Late Cenozoic ice age

A

25%

92
Q

were sea levels higher or lower in the Late Cenozoic ice age compared to today

A

LOWER

93
Q

where did land bridges connect in the Late Cenozoic ice age

A
  1. Alaska and Siberia
  2. France and England
  3. England and Ireland
94
Q

during the ending of the Late Cenozoic ice age what happened with all the melt water

A

all the water was released and covered more land than before the ice age and sea levels rose 100 ft

95
Q

describe what happens during the end of the ice age

A
  1. fresh cold water runs into the oceans but stays on the surface because it’s lighter and cause temperature inversions which prevents oceanic currents preventing atmospheric temp drops
96
Q

describe how present day COMPARES to last ice age

A

temps have risen 20 degrees and sea levels have risen 1 foot every century but it’s accelerating with human made GHG

97
Q

what point are we nearing with our accelerated GHG effect

A
  1. seeing the melting of ice caps which changes ocean currents and climatic planetary patterns
98
Q

could humans be causing an ice age sooner than natural cycle

A

YES

Geomorphology (12 decks)

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