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2115 > envs3240 > Flashcards

envs3240 Flashcards

1
Q

define weather

A

constantly changing over a period of days/months such as cyclones, wet and dry seasons and storms.

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2
Q

define climate variability

A

period of years which includes ENSO and other oscillations

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3
Q

define climate change

A

observed change over a period of decades such as global warming, SLR and ocean acidification

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4
Q

Diurnal cycles complete within:

A

24 hours such as tides?

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5
Q

seasonal cycles have transitions every:

A

3 months

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6
Q

what is a benchmark

A

an estimated set conditions that is thought to be the norm for that period - any conditions above or below the benchmark is thought to be out of the ‘norm’

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7
Q

what human actions have altered evolutionary outcomes?

A

intense harvesting, antibiotics, pesticides, genetically engineered organismsw

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8
Q

what was the first major impact of humans on the environment?

A

fire

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9
Q

when did the holocene start

A

11700 kya

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10
Q

what is ENSO

A

el nino southern oscillation with neutral, positive and negative phases. El nino is the negative phase with cooler sea temps caused by reversed trade winds. La nina is positive with warmer oceans and stronger trade winds

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11
Q

what is SAM

A

southern annular mode: influences rainfall and temp in south eastern aus. neutral, negative and positive that last 1-2 weeks.

positive sam = lower and increased rain in summer and winter in east coast

negative sam = decreased chance of rain in eastern aus and increased in west aus

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12
Q

what is the IOD

A

indian ocean dipole: changes in SST affects rainfall in Aus. negative brings less rain due to cooler water temps

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13
Q

what is the IPO

A

inter-decadal pacific oscillation

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14
Q

what are the 3 milankovitch cycles

A

eccentricity (orbit)
precession (wobble)
obliquity (tilt)

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15
Q

what is eccentricty

A

the orbit of the earth around the sun. has a periodicity of 96ka and goes from elliptical to circular which affects the glacials

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16
Q

what is obliquity

A

the tilt on earths axis. directly controls the seasons and tilts between 22.1 to 24.5˚. periodicity of 42ka.

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17
Q

what is precession

A

the wobble of the earth. caused by the gravitational pull of the moon and the sun. affects the monsoon.

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18
Q

what is a stadial

A

following an interglacial with a period of rapid cooling

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19
Q

what is an interstadial

A

following a glacial with a period of rapid warming

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20
Q

what happens to oxygen 16 during an interglacial

A

ocean gets enriched with oxygen 16 and glacials are depleted

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21
Q

what happens to oxygen 16 during glacials

A

ocean gets depleted and ice gets enriched with 16 o

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22
Q

during the last interglacial in Britain around 120kya what type of animals roamed around?

A

hippos, white lions and elephants.

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23
Q

what gives the quaternary the distinctive character?

A

the combination of high amplitude and frequency of climatic oscillations

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24
Q

what are the 3 main proxies

A

deep sea sediment cores, ice cores and speleothems

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25
Q

what causes the ratio of oxygen isotopes to change

A

temp, evaporation, precipitation and currents etc.

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26
Q

what does AMS stand for and what does it do

A

accelerator mass spectrometer. accelerates ions to high kinetic energies before mass analysis. its dissolved into a gas and ratios are measured (18o vs 16o)

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27
Q

what is fractionation

A

the breakage of 16o from 18o during evaporation

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28
Q

advantages of deep sea sediment cores?

A

MOI stages, good for global correlations. can reach millions of years of data.

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29
Q

disadvantages of deep sea sediment cores?

A

low resolution, sediment mixing, bioturbation

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30
Q

advantages of ice cores?

A

very high resolution, timing of major events, multiple proxies, time parallel horizons, independent chronology and marine-terrestial correlation

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31
Q

how long is the quaternary period

A

2.6 Ma

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32
Q

what are the names of the ice drilling stations?

A

EPICA Dome C, GISP, GRIP AND NGRIP

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33
Q

what is the age of the oldest ice core

A

800ka

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34
Q

what is the coldest and driest period?

A

interstadials

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35
Q

how many glacial cycles in the quaternary?

A

over 100

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36
Q

what are examples of proxies?

A

flowstone, varves, coleoptera bettles, loess, coral

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37
Q

what are examples of lithological evidence

A

glacial, periglacial sediments, palaeosols, loess, lake levels and sediments, wind blown, cave, deep sea sediments and ice corres

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38
Q

what are examples of biological evidence

A

pollen, diatom, plant macrofossil, fossil insect, molluscs, ostracod, formaninfera and vertebrates.

39
Q

disadvantages of ice cores

A

complex flow patterns, melting and refreezing, basal ice, very expensive and time consuming.

40
Q

advantages of speleothem dating?

A

terrestial multi proxy records, no bioturbation or diffusion, high resolution, accurately dated with U seriesd

41
Q

disadvantages of speleothem dating

A

isotopic equilbrium difficult to establish, kinetic fractionation (from evaporation), digenetic alteration, changes in isotopic ratios before entering caves

42
Q

in speleothems, when is there enriched oxygen 18 ratios

A

when there is low rainfall periods (glacials)

43
Q

in speleothems, where is there depleted oxygen 18 ratios

A

when there is high rainfall (interglacials)

44
Q

what is the most widely used biological evidence

A

pollen

45
Q

what is the connection between global warming and next ice age

A

melting ice increases freshwater discharge and disrupts the thermohaline circulation causing it to stop and cause an ice age

46
Q

is loess a glacial or interglacial feature

A

glacial.

47
Q

how can OSL signal be reset

A

light, heat and pressure

48
Q

what are the naturally occuring radioisotopes

A

Thorium, Uranium, Rubidium and Potassium

49
Q

what is more useful: inaccurate but precise or inprecise and accurate

A

inprecise and accurate

50
Q

whats the best dating technique for widest range of materials

A

radiocarbon

51
Q

how far can radiocarbon dating be used

A

60ka

52
Q

where are the oldest sediments and caves found in limestone towers

A

at the highest elevations

52
Q

what is a flowstone

A

a rock that forms from calcite flowing in layers over a flat surface

53
Q

can caves form in sandstone and lava

A

yes, including marble, karst and limestone.

54
Q

why are caves good preservers

A

capped by protected flowstone layer, protect from scavengers, protected from weathering and erosion, and rapidly build up with sediment that bury and protect fossils

55
Q

best places in aus for early modern humans

A

Kow swamp and Lake Mungo

56
Q

good overlap of humans and megafauna in aus

A

tight entrance cave

57
Q

where are key megafauna sites in aus

A

lake mungo, cuddie springs, nullabor plain and narracoorte caves

58
Q

what are sapropels

A

organic rich sediments found in the sea floor that reflect orbital precssion and indicate long term drying trend.

59
Q

what minerals are used in OSL

A

quartz and feldspar

60
Q

how are the electrons trapped in the minerals for OSL

A

in the cracks and imperfections

61
Q

what is the process of radiocarbon 14 formation

A

a nuclear reaction between neutrons produced by cosmic rays and N14 to create 14 CO2 which is taken up by organism.

62
Q

how is radiocarbon 14 measured

A

using a AMS which counts the 14c atoms

63
Q

what are the 4 ways sediment can be reset to zero

A

formation by crystallisation
extreme pressure
heating above 200-300˚C
exposure to light

64
Q

what material is used for radiocarbon dating

A

organics, carbonates

65
Q

what happens to electrons during buried sediments

A

it accumulates and gives a larger value when exposed to light in OSL

66
Q

what were some of the bridges to dispersal

A

land bridges, sea level fall, ocean currents and rainforests

67
Q

what values of o18 does ice cores have

A

-30 to -40 % per mill

68
Q

what values y axis does dust indices have

A

DD (Ca) ppm

69
Q

what values of o18 does speleothems have

A

-6 to -10

70
Q

what values of o18 does deep sea cores have

A

-1 to -3 or -100 +

71
Q

what are sapropels

A

organic rich sediments caused by monsoon which floods the nile.

72
Q

what do sapropels correlate with (2?)

A

precession (21ka cycle affecting monsoon) and long term drying trend over 3 million years which peaked at 1.8-1.6 Ma

73
Q

what does 2.9-2.6 Ma describe in africa

A

Australopiths and homo habilis emergence, however none left africa. Homo habilis was a handy man using tools.

74
Q

what does 1.9-1.6 Ma describe in africa

A

homo erectus emergence and moves out of africa using mode two tools and use of fire.

75
Q

when could homos leave africa

A

2-1 Ma due to lack of desert

76
Q

when were homos trapped in africa

A

1-0.5 Ma due to strengthening monsoon, extensive desert and Himalaya uplift

77
Q

when did homo erectus reach SEA

A

1.8Ma

78
Q

what stopped homo erectus from getting to aus

A

The Wallace line which separated marsupials and mammals and the different types of environment. erectus preferred grassy areas.

79
Q

what was at mungo 3 site

A

articulated bones

80
Q

what was at mungo 1 site

A

oldest ceremonial burial

81
Q

when was mungo dated to

A

42ka using ESR of bone and TL and OSL of sand dunes.

82
Q

where are the megafauna sites in australia top 3

A

cuddie springs, narcoorte cave and tight entrance cave

83
Q

how many animals went extinct when humans arrived in aus

A

90%

84
Q

what is the one kill per person per decade called

A

Imperceptible overkill

85
Q

what is the rapid overkilling model called

A

blitzkreig?

86
Q

how long were megafauna and humans overlapping in cuddie springs

A

15,000 years

87
Q

what happened to fire regimes during MIS 4 to 2

A

a stable and decrease in burning until MIS 2 and then a sharp increase in the holocene

88
Q

what trees had low abundance before 38ka

A

casuarina and eucalyptus

89
Q

what is accuracy in dating

A

how confident the value is, or how aligned they are with one another

90
Q

what is precision in dating

A

the range of the date +/-, how small the values are together.

91
Q

what is the importance of articulated bones

A

rapid burial which is synchronous with the sediments around it

92
Q

what kind of environments are best for OSL

A

aeolian environments

93
Q
A

2115 (9 decks)

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