Environmental Geoscience

Earth’s structure

how environmental science informs society

• plays a huge role in characterising and predicting changes to physical-chemical processes at the earth’s surface affected by human activity

• contributing to interdisclipinary environmental system analysis

• identifying trends as opposed to natural baseline variability

• what are the fundamental processes leading to the observed change?

• over what time will the change occur?

• what technologies are available to mitigate the change?

the geological record

• a record of environmental change over decades

  • e.g. Niger, Nigeria, and Chad sees loss of lakewater because unsustainably managed

• a record of environmental change over hundreds of thousands of years

• a record of environmental change over millions of years

Basalt in Melbourne

• formed from volcanoes → lava spat out, air bubbles in rock as well

• as rocks erode they become rich and fertile soils, very high in nutrients (calcium phosphate) → can sustain agriculture

granite

• forms in continental collisions

• doesn’t weather very well, very hard

• coarse textured

• coarse gravelly soil

• low in nutrients (silicon and al-rich)

• BUT good for growing wine grapes

the fertility divide

• basaltic regions

  • higher crop yields support denser populations, trade, and urbanisation

  • fertile land historically drives conflict and colonisation

  • less rich in mining wealth

• granitic regions

  • poor soil paradox → infertile land drives trade, fishing, manufacturing, emigration → outward-looking commercial cultures

  • lower agricultural value reduces land conflict

• mining regions attract investment but also resource nationalism

  • rich in mineral wealth → boom-bust economies

• BUT important to remember environmental determinism has limits

  • geologies set conditions, not destinies (climate, institutions, trade routes etc.)

    • e.g. Venezuela, DRC → should be wealthy buttt

stratigraphy

Australia’s ‘geological diary,’

2.4 billion years ago → shallow ocean floor oxygenated by early cyanobacteria (hence reddish)

white cliffs of dover → trillions of microscopic shells from warm shallow cretaceous sea, 70-100 million years ago

• sweeping curved layers in red sandstonre record ancient dunes in rid desert approximately 200 million years ago

• ‘aolian processes,’ → windblown across the desert landscape

black mineral chimneys spew 400 degree gluid from the seafloor in a mid-ocean ridge hydrothermal vent system

salt plains → white crystalline landscape in an arid closed basin due to shallow inland sea that slowly evaporated

coase sand grades to fine mud repeated in stacked layers → deep ocean floor, deposited by turbidity currents

the evolutionary ladder

• cyanobacteria meant that oxygen could be produced on earth’s surface, also therefore allowed for water

• phenezoic → cambrian explosion (lots of fossils discovered)

• geologically speaking we are in an ice-age period, in previous millions of years there were no ice caps

we’re gonna be a supercontinent one day again!

pangea ultima in 250my+

oxygen isotope ratio variations coupled to the global water cycle

you get less Oxygen 18 as you get closer to the poles bc it falls out of the sky sooner basically

interglacial vs. glacial period

• 

looking at lake and deep sea sediments, ice cores

• 3.6km of ice shows 400 000 years ago to present day

• can see glacial and interglacial periods

reconstructing paleooenvironmental history in corals

18o and Sr/Ca can reconstruct sea surface temperature

• need more than ice cores because ice cores are quite localised!

• discovered mercury contamination in south china sea during the three civil wars in China → how humans can alter the record

tree rings

• thickness of rings impacted by

  • precipitation

  • temperature

  • sun

  • soil nutrients

  • wind

• so not perfect but does show precipitation variation!

• peat sediments show historical record of lead contamination

more paleoclimate and paleoenvironmental indicators

• microfossils

  • pollen

  • frustules of protozoa (e.g. foraminifera)

• macrofossils

  • tracks

  • bones

• chemical composition

  • organic carbon concentration

  • stable isotopic composition (see oxygens above but also with other elements like carbon)

  • element enrichment (elements found in rock formation under specific environmental conditions)

  • organic molecules (’biomarkers,’)

• speleothems (stalactites)

sedimentary basin

a depression in the Earth’s crust where sediments accumulate over geological time, creating layered sequences of rock.

have layered stratigraphy, organic-rich horizons, and varying permeability

layered stratigraphy

different rock types at different depths

varying permeability

some layers store/transmit fluids, others combine them

organic-rich horizons

source of coal, oil, and gas

pore space

store groundwater, hydrocarbons, and potentially CO2

Australia’s sediment-hosted resources

• $239B in energy exports (2022)

• 6264 PJ of gas production/year

• $33B GAB economical value

formation and occurence of coal

major coal basins

Bowen, Sydney, Surat, Gaililee, Latrobe Valley

conventional formation of natural gas

• porous reservoir rock (sandstone)

• impermeable seal (mudstone/clay)

• structural or stratigraphic trap

• gas migrates and accumulates

unconventional formation of natural gas

• coal seam gas (CSG) - absorbed on coal

• tight gas → low-permeability sandstone

• shale gas → organic-rich mudstone

• no migration needed - gas stays in source

trapped by water pressure rather than structural traps

Unlike conventional gas, which migrates and is trapped by impermeable seals, CSG stays within the source coal

Coal seam gas (csg)

• methane is absorbed onto the surface of coal within coal seams

• held in place by hydrostatic water pressure

• operators pump water from coal seams to reduce pressure

• methane desorbs and flows to the surface

• associated water must be treated and disposed (extraction is fundamental to CSG)

the great artesan basin

• a sub-surface water reservoir laterally and vertically connected across sedimentary basin and lithological boundaries

• 1.7 million km2 → one of the world’s largest groundwater basins

• supports $33.2B/y in economic activity

• historically 2000ML/day extraction

  • now ~1500ML/day (improved management

• multiple aquifer layers: springbok, hutton, precipice sandstones

• supports agriculture, pastoral, mining, and town water

• other sedimentary basin resources

  • mineral sands

  • uranium

  • sedimentary iron ore

  • co2 geological storage

resource co-location

• a single column may host:

  • 0-10m: irrigation water (condamine alluvium)

  • 10-100m: groundwater

  • 100-900m: coal & CSG

  • 800-4000m: CO2

• extracting one resource changes conditions for others

condamine alluvium

• name of soil package of top 30ish m, basically the water/(soil?) that interacts with weather, very seasonally/precipitation dependent, susceptible to evaporation).

the surat basin

• 21000+ registered water bores

• 215GL/year of groundwater extraction

• 7500 active CSG wells

• 510 PJ/year CSG production

• 95GL/year of CSG associated water

• 528 bores affected

aquitard

an impermeable geological unit

petroleum system of the surat/bowen basins

• the big rig in Roma, australia’s first oil production starting in 1907

• oil occured below the seal layer for big rig

depressurisation problem

• registered water bores, 215GL extraction per year, 95 GL water from CSG

• CSG extraction depressurises the Walloon coal measures (underground coal layers that normally contain groundwater) which propogate upward through the springbok sandstone

  • When the pressure drops, water from surrounding rock layers can start moving toward the coal seams to replace the removed water.

  • Pumping water out of the coal seams pulls groundwater down from the sandstone aquifer above.

  • This can lower groundwater levels in the aquifer, which may affect springs, bores, and ecosystems that rely on that water.

condamine alluvium water table affected:

water intensity and production trends

• water intensity dropped 80% GL/PJ

• but cumulative aquifer impact continues at ~38GL/yr

  • irrigation, cattle grazing, certain crops require a lot of water

• water demand by farming → artesan basin has huge agricultural industry

  • 519.4M = gross value of western downs

water requirements for plant and animal products

how will water from CSG production be used or disposed

capacity for subsurface water storage (Acquifer managed resource)

• putting the water back into the aquifers

  • acquifers have natural filtration capacity, removes particulates

  • good in bushfires, surface water is often contaminated (ash)

  • can offset drought years, we can turn to groundwater

hydraulic conductivity

how well the ground can absorb water

low: means ground is less absorbative of water, better to mine for CSG as less water will inflow from surrounding aquifers

multi-resource development in the surat basin

• multiple resources occur in near proximity

  • oil & gas, coal, CSG, surface and groundwater

• over 100 years of resource development and economic wealth

• unconventional oil and gas production such as CSG production now requires integrated water management

• shale oil and gas production will pose further water challenges

• water is almost exclusively stored at surface leading to significant loss through evaporation

• groundwater recharge into the condamine river alluvial aquifer has large potential

groundwater recharge

the hydrologic process where surface water, such as rain or river runoff, moves downward through soil and rock layers to replenish underground aquifers

• Managed Aquifer Recharge (MAR): Intentional, engineered, or "artificial" replenishment to boost water supplies, reduce evaporation loss, and prevent land subsidence.

explain what the great artesan basin being laterally and vertically connected across sedimentary basin and lithological boundaries means for resource management when CSG operators depressurise the walloon coal measures.

alters the pressure gradient, which may cause the water to move to areas of lower pressure

condamine alluvium water level (name of soil package) → surface layer that interacts with the environment, very susceptible to seasonal/rainfall variations, susceptible to evaporation

• as CSG production increases, condamine alluvium water level (in m below surface) also increases → water level is decreasing

  • removing water from higher layers, some farmers may not be able to access water if their wells don’t go deep enough

  • extract water from the top layers to reduce the pressure on the gas trapped in the coal seams

shell build a pipeline delivering treated CSSG water to chinchilla weir, farmers pay $4/ML but face 1$60/ML if they don’t take agreed volumes. Is this equitable?

• shell benefits as farmers are responsible for building dams, storing water, bearing the risk

• encourages farmers to build dams to store the water → transferring the cost of CSG water storage onto the farmer

• but not the most equitable as shell bears no risk

the 528 registered bores that will be affected represents 2.5% of the overall 21000 bores, but are the remaining bores safe? why might this prediction be uncertain?

No — the remaining bores are not guaranteed to be completely safe. The prediction that 528 out of ~21,000 bores (≈2.5%) will be affected is based on modelling, not certainty. It means those bores are expected to exceed a “trigger” drop in water level, but other bores could still experience smaller or unpredicted impacts

• Predictions are uncertain because groundwater models rely on incomplete data, assumptions about geology, and unknown future development of CSG extraction.

stakeholders of environmental management

Queensland’s Regulatory Framework for

CSG

other potential contributors to water table decline

Legitimacy vs. Power in Resource Decisions

deep carbon cycle

• carbon influxed into oceanic sediments

  • surpentinite

    • molten interior of the earth is exposed to the overlying water column (surpentinisation and uptake of carbon within surpentenite rocks)

• carbon within oceanic crust as new oceanic crust is formed, and the mantle lithosphere

  • the whole oceanic plate is a massive carbon reservior

• as a parcel of oceanic seaflor travels it can pick up more carbons, can come close to and erode continents which deposits into the oceans

  • continental deposits get incorporated into the oceanic sediments

• eventually might find a place like a subduction zone (125km depth ish) where the oceanic seaflor is being subducted under the overriding continental crust

  • opens up pore spaces in the bending plate → water can get into, surpentinise, extract even more carbon from the surface

  • portion of the carbon stays inside the plate and becomes mixed deeper and deeper into the molten interior of the earth

  • a lot of carbon is released → devolatilisation

    • volatile gases like carbon can’t stand the pressure and temperatures at the subduction zone

    • released into mantle above, percolates into the base of the overriding continental crust

      • volcanoes → outflux and released back into the atmosphere

shorter deep carbon cycle explanation

• i.e. carbon sequestered into the plate, plate recycled into the interior of the earth, devolatilisation of the subducting plate occurs, portion of carbon is released back through the mantle and overriding plate into the atmosphere

  • repeats and repeats over millions of years

interesting stuff about deep carbon cycle

• a mass balance between influx and outflux can be observed at ocean ridges and subduction zones over geological timescales

  • divergent plate boundaries (ocean-plate ridges) contribute a lot more carbon to the atmosphere than we previously thought

    • (we overestimated volcanic arcs on the pacific rim)

plankitic calcifiers

• only evolved ~200mya are responsible for sequestering much of the earth’s emissions

  • take carbon, turn into shell/rock, die

  • build huge carbon reservoirs on the seafloor

controls on carbon sequesteration

• biological:

  • evolution of planktic calcifiers

  • dense rainforests during the cretacious

• chemical weathering of silica rocks at the earth’s surface:

  • draws down and traps carbon in the sedimentary products

  • usually deposited in ocean

    • (high strontium ratio takes too much carbon, historically an icehouse climate)

  • i.e. spreading silica crystals on beaches to wash out to sea and absorb crystals, cannot compensate for anthroprogenic emissions because it cannot be accomplished on the required scale

    • long-term, natural carbon sink

      • its natural pace is too slow to compensate for current anthropogenic emissions

chemical weathering equation

carbonate compensation depth

• depth below which calcium carbonate dissolves completely (CaCO3)

  • deeper in warm waters, shallower in cold waters (capacity of ocean to fill itself with carbon)

• i.e. if waters are too warm than CaCO3 doesn’t dissolve soon enough to store lots of carbon

ocean can store less carbon, which means more is present in the atmosphere

short-term carbon cycle

• atmosphere: CO2 traps heat → greenhouse effect → global warming

• ocean: CO2 dissolves → carbonic acid → ocean acidification

• land: CO2 feeds photosynthesis

co2 reservoirs

the keeling curve:

carbon reservoir sizes and fluxes

• land ~27%

  • vegetation

  • litter

  • soil

• ocean ~25%

  • surface ocean

  • surface biota

  • intermediate and deep ocean

  • sediment

• atmosphere ~48%

• fossil fuels and land use changes are small year-year but accumulate

• deforestation is in a significant ballpark to our fossil fuel emissions

carbon cycle and humans

fossil fuels

• solar energy stored over hundreds of millions of years, released in just a few centuries

resource vs. reserve

inferred how much of that resource we have underground vs.

• once we have a very reliable estimate it becomes a reserve

• need a means to access

growth in oil reserves (probs don’t need percentages!!)

• middle east - 47.5%

• south and central america - 19.5%

  • but e.g. venezuela, political issues

• north america - 16.9

  • fracking → only produces light crude oil which american plants can’t process, have to export all of it.

  • venezuela has all the heavy crude oil

• australia (asia pacific) by far least

  • aus has wound down oil production recently

growth in natural gas reserves

• middle east - 43.2%

• europe and eurasia

• a lot for aus → one of our largest exports

major trade movements

closure of the strait of hormuz

• affects 20 million barrels of oil per day

• 27% of global seaborne trade

• 20% of global LNG, and 84% of asia-bound share

• ~16Mb/day remains at risk even with full pipeline bypass utilisation

decline in global coal reserves

• world’s kind of had enough and is transitioning

  • mostly europe, then asia pacific, north america, middle east, s + central america

• if we burned through all our remaining coal reserves → 3-12x remaining carbon budget for 1.5-2 degrees celsius

  • we’re not running out! we’re burning too much. we have enough resources discovered

  • but supply chains matter → geopolitical risks to accessing much of our reserves (hormuz, venezuela)

• coal is growing → china and india using it to make steel for their industrial booms

types of coal power stations

• brown coal hasn’t been precooked → sits higher in the earth, contains more organic matter and hasn’t been squashed as much, black coal has already been heated and compressed a lot

• CSG emits half as much co2 as black coal

global stats

• the question of who is responsible depends entirely on your chosen metric → becomes an equity debate

  • China and india have been rising a bunch in co2 emissions

  • China is world’s largest co2 emitter

  • Australia has highest emissions per capita

  • USA has contributed most cumulative co2 since 1850

  • India, with 4x population of USA, emits half of USAs emissions

  • Australia accounts for ~1% of global emissions BUT also exports fossil fuels!

  • if remaining carbon budget were shared equally per person, Australia would need to cut emissions the most

COMPARING EMISSIONS PUNISHMENT APPROACHES

This approach divides the remaining carbon budget equally based on population size, providing every individual on Earth the same emissions allowance. → favourable to developing nations

historical: Places heavy responsibility on industrialized countries

• Based on accountability—those who caused the problem should fix it.

current-emissions basis → limits growth for developing nations but focuses on efficiency and urgency—cut where emissions are highest now.

key policy drivers of australia’s energy transition

• 2001: mandatory renewable energy target (howard government)

• 2009: RET (renewables energy target) expansion, target raised to 20% renewables by 2020

• 2011: RET split for solar and wind

• 2012: carbon price of $23/t (gillard government)

• 2014: abbot repeals carbon price

• 2015: LRET cut to 33000 from 41000 GWh, large-scale wind and solar investment stalls

• 2017: hazelwood closes (victoria’s largest coal plant) abruptly, 5 months notice, price spike

• 2018: national energy guarantee abandoned

• 2019: LRET target met ahead of schedule

• 2023: NSW’s largest coal plant closes after years of notice

• 2022+: Albanese: 82% renewables by 2030

australia’s decline in coal use

• reflects aging plant economics and corporate decisions as much as direct regulation

  • solar’s rise to 18% is largely due to the SRES (small scale renewable energy scheme) subsidy plus collapsing panel costs

  • state government took up federal government’s slack

  • private investment going up, subsidies by government

fossil fuels summary

the carbon budget and future scenarios

but 2 degrees is quite destructive

• humidity increases because ocean temps increase

• heat deaths

• pacific islands underwater

• vegetation is sensitive → coffee plantations in Brazil being moved up mountains

possible carbon futures:

three levers for emission reduction:

• reduce demand

  • energy efficiency

  • behaviour change

  • electrification

  • circular economy (minimising trade → aus is well-placed)

• decarbonise supply

  • solar and wind

  • nuclear

  • green hydrogen (though some issues?)

  • grid storage

• remove carbon

  • reforestation

  • direct air capture

  • enhanced weathering

    • spreading silica crystals on beaches to wash out to sea and absorb crystals

  • bioenergy with Carbon Capture and Storage

nuclear in europe

• france is 17x cleaner than germany

• german residents paid more than 44 euro cents per kilowatt hour compared to 33 euro cents

• when germany shut 8 reactors immediately after fukushma, carbon intensity went back up 1022-2013

• germany is much more reliant on imported gas (price spike after russia invading ukraine)

• early nuclear reactor designs have a shelf life of like 40 years

• nobody notices silent deaths caused by coal → life expectancy significantly affected by proximity to coal plants

arguments for nuclear

• zero-emissions baseload

  • near-zero co2 and runs 24/7 (unlike solar and wind)

  • australia’s coal fleet which provides ~90% of current baseload is set to retire by 2037, big gap left

• energy density and land use

  • do have to mine uranium tho

  • 3000 GWh of generation per km2

    • 62 GWh for solar

    • 872 GWh for wind

• we literally have the world’s largest uranium reserves (which we currently export)

• AUKUS precedent

  • we are investing billions in nuclear-powered submarines, yet prohibits civilian nuclear

  • we could power them ourselves

• coalition cost claim

  • the opposition modelled/argued a nuclear-inclusive plan would be ~44% cheaper than a renewables-only approach (heavily disputed)

arguments against nuclear

• too expenny

  • 1.5-2x more than renewables according to CSIRO’s GenCost 24-25

• too slow

  • at least 15 years away

    • no regulatory framework

    • no trained workforce

    • no development pipeline

  • nuclear could not be expected to produce electricity well after all coal plants are expected to retire

• Small-Module-Reactors (SMRs) are unproben comercially

  • only 3 operational SMRs globally, all in russia and china

  • no OECD-country SMR comercially has been completed

• cost overruns are the norm

  • the uk’s hinkley point c is costing 3x more than promised (~90 billion) and is running 14 years late

• renewables already winning

  • renewables continue to fall in cost

  • the cost of electricity from nuclear by 2040 would be more than for solar and wind

the nuclear option in australia

• core tension: timing vs. long-run reliability

• strongest argument: grid stability once renewables dominate

• weakest point: cannot arrive before the problem it’s meant to solve

carbon budget and scenarios summary

calculating emissions

Mtoe x 11.63 x emission factor converted to Gt (/1000)

see examples in notion

trapezoidal rule.

• calculate the cumulative emissions

• average of the start and end of the period → amount released/year

• multiply by number of years

For each scenario, calculate the required annual rate of emission reduction (% per year from the 2025 baseline) needed to reach its 2050 level. (suggests you don’t need to do increments)

groundwater use and recharge

groundwater flow in confined and unconfined porous aquifers

aquifer

• a medium of rock that water flows through

  • efficient → permeable and porous rocks

    • basalt = porus but not permeable, not effective

  • water enters and recharges the unconfined aquifer, enters and re

    charges the river through arrows around divoty thing

potentiometric surface and flowing wells

• recharge area, 2 confined aquifers, and 3 wells

  • heights correspond to water pressure inside the well

    • if well only intersects with unconfined aquifer, then height of water will be same as water table

    • if well intersects confined aquifer, hydrostatic pressure can be much greater and therefore water level can be much higher → at potentiomentric surface

undisturbed groundwater flow

minor water extraction

major water extraction

breville liquid descaler example

unconfined aquifer = squeezing a bottle with the lid off vs. confined = squeezing a bottle with the lid off, how water rises

Darcy’s law

• how to quantify groundwater flow

  • rate of water flow through a tube = Q

    • proportional to the difference in height of the water between the two ends of the tube

    • is inversely proportional to the length of the tube

    • is proportional to a coefficient K, hydraulic conductivity

• Q = volume of water flow in m3/day

• K = hydraulic conductivity in m/day

• A = cross-sectional area in m2

• dh/hl = hydraulic gradient

relating hydraulic conductivity to permeability

• the capability of a rock to allow the passage of fluids

• dependent on the size of the pore spaces and to what degree they are connected

• grain shape, grain packing, and cementation affect permeability

relating Darcy flor to velocity