#1 Flashcards
Where can we observe water in the distance universe besides Earth?
- In deep space, in a quasar system 12Ga, a mass, a black hole 20bn times as massive as our own sun. This produces energy 1000trillion times of our sun.
- quasar light highlights water vapour, 300 trillion times less dense than our atmosphere but could fill 140trillion earth oceans
- -53 degrees celcius
Talk about the abundance of water in the universe:
- After H and He, O is very abundant, H2O is most common molecule
What did William Hershal do?
- 1800’s he discovered Uranus, lots of star systems and galaxies, icy moon Enceladus.
- Hershals space observatory is great at identifying the spectral signature of water
- 2 Million oceans worth found round CW Leonis (young star), Orion nebula, disk of newly born star, around jupiter, dwarf planet Ceras. - water is not unique to us
How is water formed in the first place?
- 13.8Ga, the big bang! 1Millionth of a second after proton and neutrons can exist. 300,000yrs electrons settle in orbit around them.
- 3000 degrees celcius, 25% He, very high temp and rarely some Li
- stars produced ,most of elements, heavier elements, fusion pathways upto Fe. Anything heavier would need a super nova. The fusion pathways lead to O. So O is more abundant than any other element after that.
Where can water be found in space as ice not vapour?
- Most water in space exists as a thin layer of Ice on interstellar dust. - can’t exist in liquid fase. e.g. Snow storm behind hartley 2 comet.
- Depending on temp, transition is -170 degrees C
- Water found on Moon of Jupiter, Europas.
Why is water unique?
- Animals existing in methane or ethane/ silica based organisms. but water has properties so life an exist.
- C and H2O are building blocks of life, reason why water is so special is due to arrangements of H and O.
- 2 H have 4 electrons with 2 lone pairs. The structure of the molecule is a tetrahedra but has a positive side where the H is and negative side with the O = polarity.
- Therefore water has a great affinity for itself, its attracted to itself (sticks together).
- H bonding is a larger mass when frozen meaning ice layers can have liquid layer underneath (resist UV bombardment and need liquid water to operate metabolically)
How did water form in the solar system? How did the solar system form to produce it?
- 6Bn years ago there was a mass of gas and dust and water in a cloud
- A nearby star went super nova, causing a gravitational collapse, a chain reaction of attraction eventually forming the spiralling disc of material, a net direction determines spin direction.
- The disc collapses in on itself, the center gets hotter and hotter to create a proto star.
- Eventually creating a fusion pathway for elements upto Fe, releasing ions (solar winds) sweeping away tiny dust and gas particles
- around planets material is blown away to outer solar system = Frost line (about a Bn miles from sun), gases condense past this line
What sort of molecules condense past the Frost line?
H2O, Ammonia, CO2
How do we have water if we are in the hotter zone, pre-frost line?
- Due to solar winds and temp we don’t tend to get much of the water, instead we get metal and rock.
What marks the frost zone?
Jupiter
What happened 4.5Ga?
- The Hadean
- Collision of Tellus with Theia (mars size planet) due to eccentric orbit, which drove off more volatiles.
- Evidence - the moon is essentially dry
Where did Earth get its water from?
- In the Hadean the Earth had a similar composition to the Moon
- 0.1% of Earth is our Sea water
- Other than surface water, ringwoodite in diamond has 1.5% water, survived 500km accent, contains more water by weight than Earth
- Do we have water locked up in the mantle? How much?
- Comets and Carbonaceous Chondrites
- CC’s contain hydrated silicates, main contenders as they have a lot in common with Earth
- Francis Albarède suggested this, elements such as Xenon, Lead and water are sourced from CC. - time to land on earth e.g. Early Bombardment shown by the D/H ratio of water
- Incoming comets and meteorites can vaporize as well as add water - Late Heavy Bombardments at 3.8-.9Ga must have been significant
Are comets a good source for Earths water?
- Water can be found on comets (Garradd, Borrelly) usually forming around Jupiter where water can condense, using light spectroscopy on deep impact space probe on comet 9P Temple-1 (2005)
- D/H ratio was not the same as Earth, although some comets show some similarity/contribution (Hartley-2)
How is water important for Plate Tectonics?
(Moore and Webb, 2013)
- Moons such as Io have a relatively inactive plate tectonic system no means to get rid of pressure. They have period out bursts of lava. Forming thick cold crust.
- Heat pipes are immobile, releasing pressure. Earth was once like this until water was added!
- Water lubricates plate margins and subduction, changing the mantle composition, allows efficient convection, rocks to break more easily.
What evidence is there for water affecting the process of plate tectonics and mantle composition?
- Subduction related minerals, eclogitic garnet appear in diamonds 3Ga, or younger.
If all the ice on earth melted what would be the change in sea level?
65m
What would happen if the earth was completely covered in water?
- Algae and plankton’s nutrition that need to grow in the ocean comes from the weathering of land
Describe the nutrition cycle in the oceans today
- most nutrition is at the bottom of the ocean
- New Zealand is an exception, where there is an upwelling
- Most oceans are a desert for life (no chemical fuel) e.g. South Pacific
- Silicate weathering on land is the most important method for carbon capture.
- They are broken down to bicarbonates and dissolved silcates which are the building blocks for planktonic life
Why is the carbonate silicate cycle important?
It acts as a system of carbon control, it ultimately controls climate change, stops the runaway greenhouse effect
Facts about the South Pacific:
- you could fit all of the continents in there with rrom with another australia
- it covers about 1/3 of the earths surface
- vast majority is very clear, lack of diversity and upwellings
- ecosystems develop on rafts
What happens when there is too little water?
- water that does exist is very briney
- no processes of erosion or weathering for hydraulogical systems to exist
If the earth is covered in too much water:
- few currents and little nutrients
- we have no control over climate change
What layer of the atmosphere is at 50-60km
- The stratosphere, it has very little water, but any water that does make it there freezes and falls back to earth
Why is the stratosphere important
- It acts as a cold trap, an incredibly tiny amount of water escapes the earth.
What happens to water at subduction zones?
- The oceanic crust leaks until pore spaces are filled
- Heat at base turns water to steam which prevents water moving down
- The rock is fractured, moving and active
- Fractures mean water is subsumed into mineral structures (serpentinites) of ultramafic rocks and soft sediment, and dragged in to the mantle.
- Water is tectonically squeezed out of pore spaces and fractures, the compressed lower sediments and the ocean crust
- A slower process of de-serpentinization occurs at volcanoes, island arcs and even ocean ridges
- Worszeski et al, 2011
- OVERALL water is lost to the mantle
How is some water regained during subduction?
- Water is tectonically squeezed out of pore spaces and fractures, the compressed lower sediments and the ocean crust
- A slower process of de-serpentinization occurs at volcanoes, island arcs and even ocean ridges
- Worszeski et al, 2011
Describe the Wilson cycle:
- Diamond inclusions (eclogite garnets) suggest modern plate tectonics started ~3Ga
- Its a relatively new theory
- Showing the cycle from stable cratons (Archean slave craton NW Canada)
- Early rifting (E.African Rift valley)
- Ocean basin (Red Sea)
- subduction zones (Pacific ocean
- Collision zones orogenies (Mediterranean)
- Suturing (mountain building - Himalayas)
Who was Alexander von Humboldt?
An explorer and polymath(1769 - 1859). He found granitic rocks in S.America injected into older sediment, became a plutonist
who was Matthew Maury?
An ocean surveyor (1806 - 1873) collecting samples from the ocean floor with piano wire ad rope for depth measurement. He noticed a lump i the mid atlantic. The first recording of a MOR
What did the HMS Challenger achieve?
The Atlantic MOR was confirmed in 1872
- early microfossil work
Who was Marie Tharp and what did she achieve?
- Using sonar after the first world war confirmed the Atlantic mid ocean ridge, additionally, ridges in the Indian oceans too.
- in the 50’s and 60’s lots of data coming in and she produced the first maps
- led to expanding earth hypothesis
- however in , 1977 plate subduction was descibed but not by her
How far did the moho experditionists manage to drill?
13m
- but they got through miocene sediments and found basalt
Where does most of our ocean crust data come from?
the IODP, pure research vessel
How was sea floor spreading confirmed?
DSDP confirmed starting in 1968
- Microfossils (easily seen in boreholes)
- Eruptions at ridge
- Earthquakes at ridge
- Magnetic striping (only back to Jurassic)
- Radiometric dating (we have all ages of rock, use computers to model tectonic movement)
What are methods for reconstructing plate movements and ancient basins
- Palaeomagnetism
- Radiometric dating/isochron dating
- Biogeography/fossils
- Palaeoclimate
What is electron configuration important for?
Outer electrons important for bonding and chemical reactions
What occurred 4.56Ga?
gravitational collapse of a solar nebula
How does the composition of our sun relate to other elements found in the solar system
- Chondrites hold samples of the cloud of gas and dust from which all bodies in the solar system formed
Name the 3 types of Chondrite:
- Carbonaceous (oldest - with volatiles from early system)
- Ordinary
- Enstatite
What name is given to blobs of melt floating in our solar system?
Chondrules
What is fractionation
Separation process that splits elements into reservoirs
Carbonaceous chondrites have a similar composition to what?
The suns protosphere
How can we predict mantle composition using extrinsic information
Plot 87Rb/86Sr against 87Sr/86Sr to get a rock age from the slope of the line.
- The mantle evolution line is extrapolated created using decay constant, and thus predict the mantle composition from data collected from a meteorite
- initial 87Sr : 86Sr is useful for magma genesis, work out internal structures
What is the compostional and physical sructure of the earth?
- Crust - Lithosphere
- Moho - Asthenosphere
- Mantle - Upper Mantle
Lithosphere conducts heat, Asthenosphere/below is convection
Whats thicker crust or Lithosphere
Lithosphere
What depth is the Asthenosphere
100-200km
Which is more compatible in a matrix Rb or Sr
Sr
Is Rb or Sr more likely to go into a melt
incompatible minerals like Rb
Chondritic meteorites are more likely to have what?
a lower initial 87Sr/86Sr ratio than continental crust
What two elements besides Rb:Sr replace each other
In REE there are two elements that can also replace each other Nd:Sm
Whats the difference between Nd and Sm?
Sm has more protons, therfore, smaller and more compatable
Describe the decay process for Sm and Nd
147Sm –> 143Nd (alpha decay)
144Nd: stable isotope (= non radiogenic)
Decay constant (lambda) = 6.54 x 10^-12/a
Half life = 1.06Ga
The parent (147Sm) is more compatible than the daughter therefore:
- The crust has more Nd
- The mantle is more Sm bias
- The crust has less Sm so can’t decay to produce a high 143Nd:144Nd ratio
Describe the Sm:Nd system
147Sm –> 143Nd (alpha decay)
- In the mantle there is a high 143Nd:144Nd although originally it has a low Nd (Sm bias in mantle)
- As soon as some heat or pressure it causes melt, the 143Nd can move to a more stable area in the crust.
Describe how Sr and Nd isotopes can be used to understand mantle processes:
- Tell us which parts of the mantle that is melting
A high 143Nd:144Nd and low 87Sr:86Sr = depleted mantle (MORB) - High 143Nd:144Nd and high 87Sr:86Sr = bulk earth (CHUR = chondritic uniform reservoir)
- Ocean island basalts (come from upwellings) potential for material from lower parts of mantle, show us whats in the lower mantle, what been stirred in.
- OIB show a range from depleted mantle where MORB is towards continental crust suggesting mixing with acidic magma of continental crustal origin
What material is subducted at a subduction zone?
Ocean crust - MORB, gabbro, serpentinised
Ocean sediment - Mudstones, limestones, cherts, pelagic rain
Continental sediment - Sandstones, conglomerates
(Rarely) Continental crust - New - old sedimentary, metamorphic, igneous. - can delaminate continental crust, fall down into mantle from bottom.
Name the groups for Sr-Nd isotope data for MORB and OIB
groups represent different types of ocean island
- EM2, old continental crust returned to the mantle
- EM1, high Sr ratio but not as high as EM2 with lower Nd. Possible younger continental crust? Or pelagic sediment (geochemistry
- HIMU high Mu (238U : 204Pb), most similar Nd to MORB (least like continental crust) and lowest Sr of the 3 (Use the U-Th-Pb system to unravel what HIMU is)
- IN hydrothermal vents there’s removal of Pb from MORB, therefore more Rb but not U and Th. U, Th are not easily extracted
- Other ocean islands plot as mixtures somewhere inbetween
What are “primordial” components?
They are unaltered mantle, the mantle rock that was there at the beginning.
- We can use 3He isotopes (not formed by any endogenous terrestrial process
- 4He is radiogenic, produced by alpha decay
- we lose 3He and 4He through the atmosphere
- Plot 3He/4He showing amount of volatile escape from the mantle. MORB’s are very low on graph which suggests presence of primordial components
Whats special about He
Its the only noble gas to escape the atmosphere, lose 3He and 4He isotopes
Whats the Residence time of He in the atmosphere?
10Ma
- very unlikely to back into the mantle
- Plot 3He/4He showing amount of volatile escape from the mantle. MORB’s are very low on graph which suggests presence of primordial components
1 ltr of sea water:
- When the hydrogen dioxide is evaporated it leaves 35g of salts
- 55% chloride,
- 30.6% Sodium
- 7.7% sulphate
- 0.5 Bicarbonate, important
- everything else are trace elements of anything from the periodic table
Salt makes up what % of sea water?
3.5%
Who managed to extract 6mg of gold from sea water?
Svante Avrenius
What did Fritz Harber manage to do?
- Create fertilizer
- When recreating Avrenius gold extraction, his experiments were flawed due to human error (wore a gold ring, reused beakers.
Why is salt so common but iron isn’t, in sea watereven tho iron is so abundant in the planet? 5% of crust.
The source water for rivers is very different from sea water.
- Iron has a very low residence time (200yrs) so it precipitates out almost immediately in oxygenated water, it turns to rust (not soluble) and thus iron is taken out of the water
Whats the average river composition coming of mountains?
- HCO2 38%
- Ca 31%
- Mg 15%
- Na + K 8%
- Cl 4%
- SO4 4%
Explain how salts evaporating from sea cause terrestrial weathering
Salt from the sea evaporates as water forms cloud and precipitates down.
- The precipitation (usually rain) reacts with CO2 and SO4 to form carbonic and sulphuric acid.
- This reacts with soil/rotting organic material further increasing pH.
- Eventually it reaches rock with a pH of 5 - 3
How long does it take for all oceans to mix?
~1500yrs
- Takes neodymium ~600yrs so it can be used to trace where water flows and how far it travels and mixes
Describe the process of biological extraction/precipitation
Radiolarians drain silica from the water to make their skeletons (some use strontium)
- They die (biological precipitation) and form cherts etc and foraminifera (CaCO3)
- Original river water composition is biologically extracted
What is Abiogenic precipitation?
- In the persian gulf, a hyperconcentration of CaCO3, they are tiny microscopic particals of Aragonite
Whats a polymorph of Calcite?
Aragonite
What would happen if skeletons were made of salt?
Salt is soluble in water, it would be a metabolic nightmare!
- The more soluble elements build up in the oceans and so have long resistance times
How do tectonic accidents help in regulating salinity in the ocean
- subduction is a minor drain, a better example is the messinian salinity crisis 5.96 - 5.3Ma (the strait of Gibraltar was closed)
- Therefore evaporation is greater than water in the Mediterranean
- After evaporation 7m of salt left behind
- (Ryan, 2009)
How do seismic imaging help in regulating salinity in the ocean
Glomar challenger conducted a seismic survey in the Mediterranean, showed a salt thickness of approximately 3km in places - multiple events
- Halophiles will be the only thing able to survive
Reduction in sea level during Messinian crisis causes:
canyon formation from rivers left behind
What occured 5.33Ma
The Zanclean 10 x 108m^3/s, a huge flood triggered by an earthquake
- in a little less than 1Ma 1Mm^3 salt formed
Where in england can you find evidence of periodic evaporation?
Cheshire - rock salt from the Zechstein sea
- Permo triassic, bands of mudstone and siltstone inbetween salt + red with oxidation (terrestrial weathering)
Describe the relationship between Mg and Ca
Mg interupts CaCO3 formation - Aragonite forms instead of Calcite
What determines the amount of Mg in the sea?
The amount of sea floor spreading/tectonic activity.
Mg is used by basalt (Mg Sponge), as well as the formation of Smectite and Chlorite.
- By the same processes the less Mg there is the more likely Calcite is to be produced than Aragonite
- Mg comes into the sea from mountain/continental erosion, more continental uplift (mountain formation) = more Aragonite.
Give an example of biological use of Calcite and not Aragonite, and visa versa.
- Trilobite in Calcite sea make shells from calcite and kyton.
- Sleractinian corals maker their skeleton from aragonite
- These species were evolving at the time so it was a positive for them. Species nowadays struggle due to acidic seas/different chemical composition of the water
Oxygen in the precambrian:
Early precambrian little or no free oxygen in the atmosphere or dissolved = accumulation in the sea, this lead to green iron seas
Describe the Ocean oxygenation event:
- 3.85 - 2.45Ga No O2 in atmosphere, possible O2 in shallow seas
- Iron removed from anoxic, iron rich Archean oceans biochemically, via anoxygenic photosynthesis
- These organsims would then eventually die and fall to the sea floor to form an iron rich bang (BIF)
- 2.45 - 1.85Ga O2 becomes prominant, a major constituent in the atmosphere/oceans but absorbed into oceans and sea bed (iron mostly)
- 2.2Ga some organisms exhaled O2
- O2 produced by organisms, cyanobacteria (blue/green algae) produce O2 on mass
- This leads to a massive mass extinction of Archean anoxic bacteria and other organisms O2 is poisonous to.
- 1.85 - 0.85Ga O2 starts to gas out of the oceans, its absorbed by the land surfaces, There was no significant change in terms of O2 level
- 0.85 - present, O2 sinks filled and gas accumulates
People noticed what important feature of the sea?
the decrease in temp with depth
- (Cashin, 2007) Henry Ellis 1751 used deep sea to cool his wine down
What important figure discovered and named the Gulf stream?
Benjamin Franklin discovered current was faster from America to England - 5km/h difference
What drives the Gulf stream and the process of ocean currents?
- Sun provides energy, 174 x10^15 W
- The difference in heat at the equator creates currents.
- Heat absorbed at equator leading to evaporation of seas, which in turn drives atmospheric winds that create currents in oceans, even in deep sea
- At poles we move much slower (s = 0mph), at the equator (s = 1000mph), the rotation forms from difference in speed from equator to pole.
- This is the coriolis effect, it causes cyclones to move clockwise in N. Hemisphere and anti clockwise in the S. Hemisphere
- Hadley cells, systems circulate heat and produce winds
- Thermohaline currents
Water effectively absorbs heat:
x5 more than land as its darker in colour
What are thermohaline currents?
- Dense more saline cold sea water at the poles, it therefore sinks under sea ice and to the bottom of the ocean carrying nutrients and oxygen along the sea floor towards the equator.
- Water at the equator is heated and rises, water at the surface moves back to the poles and the cycle continues. (great oxygen conveyor belt)
- 10Mm^3/s
Stopping water flow in the Arctic:
would stop the Gulf stream, and thus change the British climate
What are Ocean gyres?
Slow moving masses of water surrounded by faster moving ocean currents (ocean deserts)
- they have no nutrition, therefore no productivity
- Coccolithophores only need sun light so they thrive, Radiolarians can also survive in oligotrophic waters due to a symbiotic relationship with small algae (dinoflagellates) in their cytoplasm. (Finley, 2005)
What happens at the contact between gyres?
Eddies form that swirl and last for centuaries.
- Large/mid size eddies, smaller ones interact with each other forming smaller ones. (track movements through thermal imaging)
Where can upwelling of nutrients be found?
As well as wind (thermohaline) upwelling of nutrients in Africa, New Zealand, S. America water on top of ocean moves faster than at the bottom, the coriolis effect creates a spiral that pulls nutient rich water upward
- The Ekman transport vector, the 3rd important vector for ocean currents (Korgen, 2016)
Describe the effect of nutrients and life in the deep ocean:
The deep ocean still has diverse but slow cold water life. An important form of nutrient is marine snow (calcareous material, faeceas, dead stuff), crinoids eat it on the abysall plane.
Describe and explain nutrition in the Cretaceous oceans and the impact on life:
- The ocean currents were different from now, no polar ice caps
- A huge diversity of life in the Antarctic ocean
- No large scale eddies, only smaller localised ones so lower diversity world wide
- Ocean anoxic events, likely to happen again to us due to CO2, black shales in chalk (nothing to eat organic shale)
- Sea levels 100m higher, due to melted ice and larger mid ocean ridges displacing water, more water on continental shelf could have been an advantage for marine life?
What is the definition for the origin of life:
Complex ordered structures that require extraction of energy and materials from surrounding, less ordered environment and have the capacity for self replication.
Any initial Archean life withstood:
the late heavy bombardment (3.8 -3.9Ga)
What is abiogenesis
Aristotle came up with the theory that life spontaneously came from matter
- 1668 Francesco Redi did the maggot, meat beaker experiment
- 1861 spontaneous generation proved incorrect by broth boiling, tube, experiment
What is the inorganic model?
Clays, like kaolinite, have complex structures and serve as a base for life, information is replicated across layers of crystal growth
- silicate solution with organic interaction, inorganic became organic
- Results are inconclusive, not much evidence
Describe the Biochemical model
- Oparin and Haldane (1920’s)
- Miller-Urey experiment (1950’s)
- production of amino acids, recent reanalysis showed 22 amino acids and 5 amines
- proved there are gene + enzyme in the 60’s
- membrane can’t be produced with RNA
- DNA, RNA and membranes play a large role in the step by step evolution of life
- Atmosphere used in experiment not consistent with recent findings
- Huge leap to go from complex chemistry to a single cell like a prokaryotic cell.
Panspermia:
- seeded from meteorites (organic compounds found on carbonaceous chondrites) - Fred Hoyle
- very unlikely a single cell could survive the impact, lethal radiation, cosmic rays
- Doesn’t explain origin
Darwin’s warm little ponds:
Primordial soup, UV needed to cause chemical reactions
- The most evidence for this
Hydrothermal vents:
- energy from oxidation of hot reduces sulphur compounds
- LUCA is a hyperthermophile - bacteria that can be found there act as a base for life
What are some constraints with the origin of life theorys?
- High UV radiation and meteorites bombardment of Early Earth
- Microfossils, early forms are argumentative
What fossil evidence is there for early life?
- Haematite tubes 3.77 - 4.22 Ga in Canada
- minerals or life?
- some isotope carbon evidence - Carbon films, structure of graphite in 3.7Ga
- metamorphic schist but its very controversial
structures - Fossil cells 3.4Ga western Australia in cherts (Wacey et al, 2011)
- Stromatolites
- Bangiomorpha
Describe the evolution of early life:
~ 3Ga
- Shark bay Australia
- initial substrate with blue green algae + sediment and then more algae
- pump out oxygen
- O2 is poisonous to other Archeans
- Iron precipitation and anoxia (BIF)
- Great oxygenation event - 2.4Ga Bad for obligate anaerobes
- Life isn’t prokaryotic until 1.7Ga
- Endosymbiosis - Lynn Margulis 1967
- Bangiomorpha at 1.2Ga - no more mitosis, its now meiosis
- allowed genetic variation but lower numbers for the energy involved
- Complex 3D shapes ~650Ma
Describe endosymbiosis
- Eukaryotes formed from a host prokaryote fusing with other prokaryotic cells of different functions to form a nucleus and organelles
What was the impact of complex 3D shapes such as sponges
650Ma - By filter feeding they began to clean up the Proterozoic oceans - there was more oxygen and more light penetration as the water became cleaner.
- Other organisms began to eat them creating ecological tiering
- Soon lead to Ediacarans 580Ma
Fossil evidence following the origin of life: Ediacarans:
- Sudden infusion of O2 in ocean 580Ma
- 1957, Roger Mason discovered Charnia
- Some ediacarans had bilateral symmetry, Kimberella, meant vagrant mode of life, movement
- Large leap in history was in Chengjiang biota, Maotianshian shales ~530Ma, show all animal groups
- worms, velvet worms, shrimp,
- Myllokunmingia, possibly the earliest cordate, similar to most basic fish
- Some Australian fossils known but age is poorly constrained, so only assumed to be Cambrian.
Various changes in biota diversity in the ocean through time:
- Devonian, Rhynie Chert show evidence of animals and plants on mass evolving to survive and edapt to life on land yet just in the mammal family, ~50Ma, in the Eocene Pakicetus, then later Ambulecetus, began life back into the oceans
- Snakes back in the water
- Iguana and turtles
Increased fishing methods:
End of 1970’s cod population decimation, Carnivores, eat crustaceans like shrimp.
- Humans fish down the food chain: once we find a large species like blue fin tuna, we hunt it to extinction (next 10yrs no blue fin)
- This would have a large impact on diversity, predators that control the food chain
- loss of sharks in the sea of Cortes, replaced by Humboldt squid, sea of death
- Whitebait is baby herring, so no more wild herring
- fish farming is destructive
- However, there is some hope, fresh water farming is on an increase
What are the effects of trawler nets
They destroy reefs, they decimate everything, usually looking for one species of shrimp.
- Also creating turbidity currents after trawling meaning erosion of continental shelf, further reducing chance of recovery
Following the 1950’s plastic boom:
A cumulative increase in plastic items and plastic use
- Only <10% all plastic is recycled
- It degrades as the bonds are strong until its very small, only then do the bonds break, this induces a plastic ooze/durable grains of plastic floating in our oceans
- sewage plants can’t process micro plastics and fibres
- 6Mt into ocean every year
- Great S.Pacific garbage patch - gyre
- 9/10 beaches contain plastic
- Half of it floats half of it sinks
- By 2050 plastic will outweigh fish in the ocean
What happens to the plastic in our ocean?
once it has broken down, 10yrs after toxins are released. It absorbs inorganic and organic toxins like fertilizer and DDT, these are consumed by zooplankton and make their way through the food chain.
Whats the CO2 rise from 1960 to current day?
~280ppm to ~400ppm
CO2 is way:
higher than normal fluctuation
- argue that its due to mylankovitch cycle
- however 1950’s onwards we have burnt more hydrocarbons than the sum of that before, so probs not
Most of the suns heat is stored:
In the ocean.
- leading to ice melt, 200 -300Mt melt per year
- Reduced albido effect
What occurs as the polar ice melts:
- Ice caps reflect less heat
- decreasing salinity at poles effecting the life and global circulation of nutrients
- 430Gt +/- 230Gt over the past few years
- Start to lose continental shelf, decreasing photic zone, more flooding, fewr reefs/biodiversity
- in a few centuries = sea level will rise 10m
What do temperature profiles in the ocean show?
- Ocean water stratification
- summer has thermocline (difference between warm and cold water), winter does not.
- There is a thermocline all year round now which means no nutrient flow from depths
Effects of ocean acidification:
calcite/aragonite pH requirements for precipitation with increasing CO2
- carbon flux absorbed by oceans makes it more acidic
- 1/3 of carbon released from burning hydrocarbons goes into the ocean
- oceans are about 0.1pH unit more acidic (30% more H+ ions), they are naturally more alkaline, which would support its life
- As we increase temp + CO2, it reduces O2 in seas, when 7pH is reached corals + planktonic organisms start to dissolve and become weaker, often destroyed by storms/environmental pressures
- Corals release algae inside once a temp is reached
What is the predicted shrinking of coral reefs
560ppm
Why can coccolithophores cope better with ocean acidification
They are made of calcite not aragonite
Whats the main reason for marine eutrophication
Main reason for our population increase + spreading population, we produce nitrates/phosphate fertilizer and almost doubled in use, which is still increasing.
- Eutrophication in oceans caused by fertilizer in oceans, causing a massive increase in algae, killing photosynthetic organisms beneath, bacteria eat the alage => dead zone. e.g. Gulf of Mexico
Whats the spreading rate of dead zones
~250,000km^2
Where are oceans disappearing?
Into the crust
- subducted into mantle
- serpentite
- 1km^3 of water lost per year
- estimated we will lose 1/4 of our water, making the sea more salty and smaller over time (Worszeski et al, 2011)
What will happen to life in the future of our planet?
- Sun is getting hotter and brighter, meaning more evaporation and methane.
- Stratosphere will go so we can’t hold onto our water, we will lose ions into space as temp increases
- Earths core will begin to cool so we lose are magnetic field for protection against solar winds
- Salt eroded from old deposits like Zechstien and Med. go back into the oceans meaning eventual death for all life on earth
- Greenhouse effect begins to melt rock
- 5bn yrs from now red giant forms and the earth is engulfed or melted
What did Svante Avrhenius discover
(1859 - 1927)
- Used wavelengths of light to interpret planetary atmosphere or water
- Mars is a freeze dried planet
- Mercury has almost no water
Mars:
- Mars has white poles, and linear features (noted by Avrhenius) which are canals
- -120 degrees C at poles and -5 at equator
- thin atmosphere, pressure 1% of earths, mainly CO2
- Sedimentology and topography to back up evidence o water, alluvial fans found like those found in death valley.
- High concentration of deuterium
Mercury:
- No water
- In hospitable for water, bright patches may be water or sulphur but they have to survive solar winds
- -150 degrees C at night, 425 degrees during the day
Venus:
- Behind venus’s thick veil of cloud, its very bright in the sky
- Clouds are mainly droplets of concentrated sulphuric acid
- ~400 degrees C at surface
- pressure to high to support any cells
- tiny amount of water (deuterium), due to run away greenhouse = loss of water to space
- Lower density than earth, probably had an iron core but it cooled = solar wind bombardment
Jupiter:
- water vapour (thin) in vast amounts
- Europa
- Ice covered in channels and relatively smooth
- Possible subsurface ocean and ice tectonics, water depth 100km, total volume 3bn km^3
- occasional geysers from surface
- periodic water leaves the moon into space
Saturn:
Enceladus has geysers and water at surface, zero pressure or heat underground?
- water depth 10km
- total volume is unknown
Titan has hydrocarbon seas, largest shown on radar images, Kraken mare 1000km across, and water ice boulders on the surface
- Ammonia water ocean inbetween 2 layers of ice`
Dwarf planet Quaor:
Located in the Kuiper belt
- half the size of pluto
- has crystalline ice at the surface
- cryovolcanism, lots of ammonia and methane fueled by radioactive decay of its core
Finding more exoplanets:
Transit - detect them when they are eclipsed infront of the nearby star causing periodic dimming, most in 2014.
Wobble - the planet’s gravitaional pull can make their parent star wobble
Direct observation - light given off when starlight is rid off or reflected off a planet
Oceans beyond our solar system:
- Trappist-1, an ultra cool red dwarf star in the Aquarius constellation, 7 terrestrial planets orbiting (Witze, 2017)
- Canri 55e, wierd water world with a super heated/supercritial water, possible CO2 planet or solid diamond
- Keplar 22b may be a true ocean world (in the habitable zone), goldilocks point from star
How far across is the Milkyway
100,000 lightyears
Most of rocks:
- Don’t have biostratigraphic record to date them
Can use strontium isotopes:
- can use strontium isotopes to work out continental erosion, ocean deposition and how much ocean crust is being formed
Whats the principal feature in any mineral
- Closure temperature
- high temp elements can move and equilibrate according to partition coefficients
- For any given temp, elements may be able to move in or out of a mineral phase, as temps go down minerals close their doors
e.g. U - Pb
Zircon >750 degrees C
Sphene >650 degrees C
How do you test ranges of closure temperature
If we work out amount of radiogenic nuclide remaining in the mineral we can work out closure temp.
Name some high temp range minerals U-Pb
- Garnet
- Zircon
- Allanite
- Monzanite
- Sphene
Name some medium temp range minerals Ar-Ar
- Hornblende
- Muscovite
- Biotite
- K-feldspar
Name some low grade low temp range minerals (U-Th)/He
- Fluorite
- Apatite
- Zircon
- Sphene
What make the best chronometers
High parent isotope/daughter isotope ratio
