envs3240 Flashcards
define weather
constantly changing over a period of days/months such as cyclones, wet and dry seasons and storms.
define climate variability
period of years which includes ENSO and other oscillations
define climate change
observed change over a period of decades such as global warming, SLR and ocean acidification
Diurnal cycles complete within:
24 hours such as tides?
seasonal cycles have transitions every:
3 months
what is a benchmark
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’
what human actions have altered evolutionary outcomes?
intense harvesting, antibiotics, pesticides, genetically engineered organismsw
what was the first major impact of humans on the environment?
fire
when did the holocene start
11700 kya
what is ENSO
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
what is SAM
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
what is the IOD
indian ocean dipole: changes in SST affects rainfall in Aus. negative brings less rain due to cooler water temps
what is the IPO
inter-decadal pacific oscillation
what are the 3 milankovitch cycles
eccentricity (orbit)
precession (wobble)
obliquity (tilt)
what is eccentricty
the orbit of the earth around the sun. has a periodicity of 96ka and goes from elliptical to circular which affects the glacials
what is obliquity
the tilt on earths axis. directly controls the seasons and tilts between 22.1 to 24.5˚. periodicity of 42ka.
what is precession
the wobble of the earth. caused by the gravitational pull of the moon and the sun. affects the monsoon.
what is a stadial
following an interglacial with a period of rapid cooling
what is an interstadial
following a glacial with a period of rapid warming
what happens to oxygen 16 during an interglacial
ocean gets enriched with oxygen 16 and glacials are depleted
what happens to oxygen 16 during glacials
ocean gets depleted and ice gets enriched with 16 o
during the last interglacial in Britain around 120kya what type of animals roamed around?
hippos, white lions and elephants.
what gives the quaternary the distinctive character?
the combination of high amplitude and frequency of climatic oscillations
what are the 3 main proxies
deep sea sediment cores, ice cores and speleothems
what causes the ratio of oxygen isotopes to change
temp, evaporation, precipitation and currents etc.
what does AMS stand for and what does it do
accelerator mass spectrometer. accelerates ions to high kinetic energies before mass analysis. its dissolved into a gas and ratios are measured (18o vs 16o)
what is fractionation
the breakage of 16o from 18o during evaporation
advantages of deep sea sediment cores?
MOI stages, good for global correlations. can reach millions of years of data.
disadvantages of deep sea sediment cores?
low resolution, sediment mixing, bioturbation
advantages of ice cores?
very high resolution, timing of major events, multiple proxies, time parallel horizons, independent chronology and marine-terrestial correlation
how long is the quaternary period
2.6 Ma
what are the names of the ice drilling stations?
EPICA Dome C, GISP, GRIP AND NGRIP
what is the age of the oldest ice core
800ka
what is the coldest and driest period?
interstadials
how many glacial cycles in the quaternary?
over 100
what are examples of proxies?
flowstone, varves, coleoptera bettles, loess, coral
what are examples of lithological evidence
glacial, periglacial sediments, palaeosols, loess, lake levels and sediments, wind blown, cave, deep sea sediments and ice corres
what are examples of biological evidence
pollen, diatom, plant macrofossil, fossil insect, molluscs, ostracod, formaninfera and vertebrates.
disadvantages of ice cores
complex flow patterns, melting and refreezing, basal ice, very expensive and time consuming.
advantages of speleothem dating?
terrestial multi proxy records, no bioturbation or diffusion, high resolution, accurately dated with U seriesd
disadvantages of speleothem dating
isotopic equilbrium difficult to establish, kinetic fractionation (from evaporation), digenetic alteration, changes in isotopic ratios before entering caves
in speleothems, when is there enriched oxygen 18 ratios
when there is low rainfall periods (glacials)
in speleothems, where is there depleted oxygen 18 ratios
when there is high rainfall (interglacials)
what is the most widely used biological evidence
pollen
what is the connection between global warming and next ice age
melting ice increases freshwater discharge and disrupts the thermohaline circulation causing it to stop and cause an ice age
is loess a glacial or interglacial feature
glacial.
how can OSL signal be reset
light, heat and pressure
what are the naturally occuring radioisotopes
Thorium, Uranium, Rubidium and Potassium
what is more useful: inaccurate but precise or inprecise and accurate
inprecise and accurate
whats the best dating technique for widest range of materials
radiocarbon
how far can radiocarbon dating be used
60ka
where are the oldest sediments and caves found in limestone towers
at the highest elevations
what is a flowstone
a rock that forms from calcite flowing in layers over a flat surface
can caves form in sandstone and lava
yes, including marble, karst and limestone.
why are caves good preservers
capped by protected flowstone layer, protect from scavengers, protected from weathering and erosion, and rapidly build up with sediment that bury and protect fossils
best places in aus for early modern humans
Kow swamp and Lake Mungo
good overlap of humans and megafauna in aus
tight entrance cave
where are key megafauna sites in aus
lake mungo, cuddie springs, nullabor plain and narracoorte caves
what are sapropels
organic rich sediments found in the sea floor that reflect orbital precssion and indicate long term drying trend.
what minerals are used in OSL
quartz and feldspar
how are the electrons trapped in the minerals for OSL
in the cracks and imperfections
what is the process of radiocarbon 14 formation
a nuclear reaction between neutrons produced by cosmic rays and N14 to create 14 CO2 which is taken up by organism.
how is radiocarbon 14 measured
using a AMS which counts the 14c atoms
what are the 4 ways sediment can be reset to zero
formation by crystallisation
extreme pressure
heating above 200-300˚C
exposure to light
what material is used for radiocarbon dating
organics, carbonates
what happens to electrons during buried sediments
it accumulates and gives a larger value when exposed to light in OSL
what were some of the bridges to dispersal
land bridges, sea level fall, ocean currents and rainforests
what values of o18 does ice cores have
-30 to -40 % per mill
what values y axis does dust indices have
DD (Ca) ppm
what values of o18 does speleothems have
-6 to -10
what values of o18 does deep sea cores have
-1 to -3 or -100 +
what are sapropels
organic rich sediments caused by monsoon which floods the nile.
what do sapropels correlate with (2?)
precession (21ka cycle affecting monsoon) and long term drying trend over 3 million years which peaked at 1.8-1.6 Ma
what does 2.9-2.6 Ma describe in africa
Australopiths and homo habilis emergence, however none left africa. Homo habilis was a handy man using tools.
what does 1.9-1.6 Ma describe in africa
homo erectus emergence and moves out of africa using mode two tools and use of fire.
when could homos leave africa
2-1 Ma due to lack of desert
when were homos trapped in africa
1-0.5 Ma due to strengthening monsoon, extensive desert and Himalaya uplift
when did homo erectus reach SEA
1.8Ma
what stopped homo erectus from getting to aus
The Wallace line which separated marsupials and mammals and the different types of environment. erectus preferred grassy areas.
what was at mungo 3 site
articulated bones
what was at mungo 1 site
oldest ceremonial burial
when was mungo dated to
42ka using ESR of bone and TL and OSL of sand dunes.
where are the megafauna sites in australia top 3
cuddie springs, narcoorte cave and tight entrance cave
how many animals went extinct when humans arrived in aus
90%
what is the one kill per person per decade called
Imperceptible overkill
what is the rapid overkilling model called
blitzkreig?
how long were megafauna and humans overlapping in cuddie springs
15,000 years
what happened to fire regimes during MIS 4 to 2
a stable and decrease in burning until MIS 2 and then a sharp increase in the holocene
what trees had low abundance before 38ka
casuarina and eucalyptus
what is accuracy in dating
how confident the value is, or how aligned they are with one another
what is precision in dating
the range of the date +/-, how small the values are together.
what is the importance of articulated bones
rapid burial which is synchronous with the sediments around it
what kind of environments are best for OSL
aeolian environments
