Earth Science Summaries *when reading through this, when it comes to diagrams, draw them on paper! TECTONIC IMPACTS Lithospheric (crust and upper mantle) plates characteristic are very different: Oceanic Continental Density 3.1g/cm 3 2.7g/cm 3 Composition Mafic- basalt, gabbro, dolerite Silica rich (felsic) mixed e.g. granite and sedimentary Thickness 7km 60-100km Age <200my 3.8by Primary wave speed 7km/s 6km/s There is a relationship between rock composition and plate boundary: Divergent- Mafic, low quartz (oceanic) Convergent- Felsic, varied, (continental) Convection currents and subduction drive plate motion Heat from core hot rise-cold sink. Less dense float. Convection is very slow in solid mantle. Hot, less dense basalt made at MOR. Colder, denser subducts MOR. SLAB PULL- denser subducting plate sinks down into mantle- pulls plate with it. RIDGE PUSH- MOR- plate is higher up and hotter/less dense. Gravity pulls plate down into mantle at subduction zone. TRENCH SUCTION- 2 converging plates- subducts. One subducts and convection current occurs. Sucks plates together. WHAT RESISTS MOTION? COLLISION RESISTANCE- two plates resist each other at subduction. SLAB RESISTANCE- friction between subducting plates resists motion Tectonic super cycle takes 400my: 20my- super continent (PANGAEA). Thick, cold climate, low co2 + sea- level.
Transcript
Earth Science Summaries
*when reading through this, when it comes to diagrams, draw them on paper!
TECTONIC IMPACTS
Lithospheric (crust and upper mantle) plates characteristic are very different:
Oceanic ContinentalDensity 3.1g/cm3 2.7g/cm3
Composition Mafic- basalt, gabbro, dolerite Silica rich (felsic) mixed e.g. granite and sedimentary
Convection currents and subduction drive plate motion
Heat from corehot rise-cold sink. Less dense float.Convection is very slow in solid mantle. Hot, less dense basalt made at MOR. Colder, denser subducts MOR.
SLAB PULL- denser subducting plate sinks down into mantle- pulls plate with it.RIDGE PUSH- MOR- plate is higher up and hotter/less dense. Gravity pulls plate down into mantle at subduction zone.TRENCH SUCTION- 2 converging plates- subducts. One subducts and convection current occurs. Sucks plates together.WHAT RESISTS MOTION?COLLISION RESISTANCE- two plates resist each other at subduction.SLAB RESISTANCE- friction between subducting plates resists motion
Tectonic super cycle takes 400my:
20my- super continent (PANGAEA). Thick, cold climate, low co2 + sea-level.70my- heat builds up underneath plate. Extension and sagging of crust.70my- super continent splits. Co2 rise + sea level + temp. MOR form.75my- rapid seafloor spread. High co2, temp, sea level, lots of MOR, high plate movement.165my- continents come together. Low sea level, co2, temp. COLD. Super continent getting made.
Plate motion and types of boundaries: ROTE LEARN.Aus. –Indian- northsouth American- westpacific- east
north American- NWNazca-east
Eurasian- eastDIVERGENT- MOR, Graben, mafic igneous, shallow quakes, transform faults.CONVERGENT- Ocean-ocean: subduction, island arc e.g. Indonesia. Ocean continent: subduction, volcanic mountain e.g., ANDES. Continent- fold mountains Himalayas.
1906 San Fran Quake is likely to occur again:
Gas lines- fires. 3000 dead. WHAT PLATES? N.A and North Pacific. San andreas fault rupture. WHAT HAPPENED? Strike slip movement of the plates. NP- northwest. NA- southwest. Released pressure in a quake. 7.9 magnitude- rupture in fault spread north and south 476 km. displaced ground 6m. Main shock most destructive-42 seconds. Reclaimed San Fran bay soil liquefaction. Untrained firemen used dynamite to make firebreaks- more fires.DISTANCE FROM DISASTER AREA- epicentre offshore san Fran. plate movement 300km north San fran. PROBABILITY- 80% chance quake 6.2 or higher. Continual plate movement- pressure has to be released somehow.HOW TO PREDICT- Geiger counter- radon gas released from crystals cracking from high plate movement. Seismometer- monitors p and s waves. Bigger time difference between waves means bigger distance device is from epicentre. Triangulate results to locate epicentre. Use past data to predict where a quake will occur and when.HOW TO MINIMISE EFFECTS OF QUAKES- Good warning systems- TV, radio, newspapers, loudspeakers in major cities, good training and coordination of emergency services, ensure all households have emergency kits ready e.g. clothes, food, water, masks to stop dust inhalation etc. Build in reduced risk areas- map geotechnical hazards and computer simulation of quakes. Better local building codes. Quake proof buildings- BASE ISOLATION- Teflon pads or springs separate building from ground. Reduced shearing forces. DIAGONAL BRACING- braces across building keeps it intact made from wood or steel. STRONGER FRAMEWORKS- reinforced steel > masonry.
Faults and folds cause different mountain structures DIAGRAM: Anticline, syncline, monocline, recumbent, overturned. Results in shortening and thickening of crust.FaultsNormal = divergent. Reverse/thrust (two come together and push up a bit). Conservative= strike slip. Horst- bit pushed up (convergent). Graben- (divergent) layered stairs kind of thing. Faults occur because brittle rocks crack instead of fold.
Mountains and structures depend on boundary type DIAGRAM:
Divergent oceanic: MOR, most extensive mountain ranges, 1000km wide, 3000m high. Layers of rocks- basalt, sheeted dyke, gabbro on bottom.
Divergent continental: rift valleys, African rift valley, less than 100km wide, less than 300km high, normal faults, graben. Mafic igneious-0 basalt.
Convergent continental C & C: folds, reverse faults, graben, ophiolites, metamorphic e.g. gneiss, schist. Mt Everest
O & C convergent: subduction zones. Andesite, rhyolite, igneous, volcanic mountains, mountains made from compression and uplift of rock and sediment, highly faulted and folded sedimentary rocks.
O & O convergent: volcanic island arc, subduction. Explosive volcanoes and fold mountains INDONESIA.
Aus. through time DIAGRAM:
Achaean- Pilbara Yilgarn. 3.8. ByProterozoic- north Aus. Cratonised. Gawler craton west of Adelaide. Central Aus. Mobile belt active- not cratonised until end of era.Palaeozoic- Tasman fold beltCambrian- Volcanic island arc Vic. Ordovician- Narooma subduction.Silurian/Devonian- Subduction zone went eastCarboniferous/Triassic-Aus. Was extended by coastal extension. Subduction zone attached to land and accreted a lot of sediment and magma
onto old cratons e.g. Pilbara and Lachlan Fold Belt. Sediment which become the land. Sydney basin made.Cretaceous to present- rifting on SE edge of Aus. PNG mobile belt.
CRATON= old stable piece of continent crust. MOBILE BELTS= active part of crust with subduction zones and collision boundaries, they are highly deformed with metamorphic rocks. EVIDENCE- WA rocks 3.9. by lot older than rocks on East Aus.
Rock types at mountains:
Mountains made by Formation Rock type Structure in mountainsUplift and rifting Divergence MOR,
Mount Pinatubo 1991 5km3 of magma and ash and dust could 40km high Huge clouds in stratosphere Injected 17 megatons SO2---- made aerosols reflect solar radiation---moved around globe—
global cooling of 0.5 degrees. Eruption and effects stronger than effects of global warming and El Nino at the time.
Earthquakes and volcs. occur at plate boundaries:
Convergent= deeper quakes due to benioff zone and thick lithosphereDivergent= shallow quakes due to transform faults along MORSubduction= explosive composite cones.EPICENTRE= surface. FOCUS= underground (where it happened).
Many technologies exist that can predict quakes and volcs:
Quakes Volcs.Groundwater level and temp- rise before a quake. Need thermometer in groundwater monitoring constantly. ALREADY COVERED IN SAN FRAN
Steam from vents- increase before eruption.Change in gas levels- more hydrogen, CO2, water, H2S before eruptionVegetation dieback- happens a while before
eruption. Toxic gases kill them.Gravity and tilt meters- magma rises before eruption. Volcanoes change shape as magma risesLasers- detect change in shape of cone.GPS- of cones position is altered on GPS map, eruption soon.
People live in dangerous zones for many reasons:
High altitudes= good rainfall. Clouds condense on mountains. Rich soils= high trace elements + high rainfall =good for agriculture. Grow rice. People forget about eruptions because they’re infrequent- stories aren’t passed down
through cultures. Cultural value to volcanoes- religious beings. Pop. Pressure- no land means forced to live in risky areas.
Shockwaves from quakes are disastrous:
P, S, L waves. L most destructive. Impact depends on proximity to epicentre, type of wave, intensity of quake and type of substrate (ground).
Natural BuiltLandslides Soil liquefaction: reclaimed swamps. Makes
quicksand.Tsunamis: coastal regions get hammered. Change river direction. Also destroy built e.g. Japan 2011.
Destruction of buildings: rigid masonry is bad.
Forests get destroyed: only in huge quakes. Fires: broken gas mains and power lines. Water lines get broken. Can’t extinguish.Flooding: Dam walls break.Roads destroyed: Can’t get emergency services to areas easily.
Volcanoes are dangerous lots of hazards:
Poisonous gases: asphyxiate e.g. Lake Nyos (sleeping African town all dead at night from gas from lake). Sulfuric acid formed- destroy lungs.Ash flows: pyroclastic flows. Gas and dust. 200km/hr, 400 degrees. Travel up to 20km. destroy everything. Composite cones.Lahars: Hot mud. “Dams” of debris on cones break with rain from eruption. Shaking from cone and
lots of rain – race down hill. Max destruction. Move down water courses- dangerous areas for people.Lava flows: Common with shield volcanoes.
Types of volcanoes:Plinian eruption: Stratosphere. Ash is aircraft hazard- clog engine. Global cooling.Shield volc: Hot basaltic lava, high silica, low viscous lave (runny), 1200 degrees. Not explosive. Composite cone: Explosive, cooler felsic lava 850 degrees, viscous lava. High dissolved gas. Magma rises in cone, pressure reduces, gas out of solution makes high pressure in cone- explosive from side = lateral blast, gas escapes. Pyroclastic flow.
Research into prediction of quakes and volcs is justified:
For: Against:Reliable early prediction = less death Too difficult to predict quakes. Money better
spent on hazard reduction e.g. safety measures and better houses.
High cost of technology to predict is low cost compared to loss of life. Is there a price on a life?
Warnings cause panic and stampedes- death
Computers and remote sensing has greater prediction potential
Better to spend money on education of people about how to live with the hazards e.g. what to do in a quake.
Unreliable prediction of events will mean people won’t move to safety because they think event won’t happen
Volcs easier to predict.
Cristal movement at collision boundaries can be predicted:
Technology How does it work?Laser geodimeter Measures change in distance between stationary
recording stations on opposite sides of a boundary. Detects movement.
10m long wire strain gauge Measures strain and change in surface of ground at fault line.
Tilt meter Ground tilting.GPS measurements Measures distance plates have moved from a
satellite. Bases measurement from stationary recording stations either side of converging plate.
1989 Newcastle quake occurred intra-plate:
5.6 Richter and shaking felt 200,000km2 in NSW. Old fault line under Newcastle reactivated with coal mining. Water pumped out to keep
mine dry. Stress on rocks increased. Coal extraction deformed crust. Deformation over time got too much---- pressure released in quake. FOCUS- 15km SW Newcastle shallow 10km depth. Disastrous because city buildings not built for quakes. $4 billion damage.
Natural disasters are focused round plate margins ASSESS:
DISASTER ABOUTKrakatoa 1883, tsunami, quake and volcano, 2000 death.Sumatra Quake and tsunami, 200,000 dead, 9.1 Richter,
2011Assess: natural disasters are focussed, more frequent and violent around destructive plate margins. Forces acting on plates cause huge pressure and energy released- sudden movement occurs as plates slip past each other. Hypothesis arguing for this are correct.
Plate margin and intra-plate quakes are different:Most severe at plate boundaries, intraplate less severe. INTRAPLATE AUS- Aus. Plate move north, stress and compaction, existing fault lines are where quakes occur, heat flow from asthenosphere changing is also a cause.
Plinian eruptions cool then warm planet- affect local and global climates:
Lots of gas in eruption. Green house gases absorb suns infrared. WARM. Sulphuric acid causes fine milky aerosol. COOLING GLOBALLY. Scale of eruption alters degree of cooling. Stratosphere >15km- no weather so aerosol stay for long time. Wind in troposphere spread aerosol. CO2 in atmosphere from eruption later causes warming
LOCAL GLOBALSeverely affected- ash smothers crops. 1883 Krakatoa. Heavy rain and lahars washes away crops and infrastructure.
Global cooling. Slow crop growth. 1815 Tambora reduced temp by 3 degrees.
No light due to clouds- can’t grow crops Ash and aerosol block sunlight- no photosynthesis.
Acid rain destroys crops and stock- no food for stock.Ash smothers crops and stock- dead. Poisonous gas kill stock and crops -1783 Laki eruption. Pyroclastic flow kill everything- Pinatubo 1991.Area affected >100km.
Plate tectonics affect the climate:
Single eruptions only reduce temp by few degrees. ICE AGES CAN BE CAUSED BY MANY THINGS- 11 year solar cycle, changes in Milankovich
cycle- earth orbit and tilt change, Bolide impact- cooling from dust, warming if bolide hits limestone deposit- CO2 in atmospheres, Plate tectonic supercyle- warming and cooling as super continent breaks and forms. SNOWBALL EARTH WHEN A SUPER CONTINENT EXISTS.
ENVIRONMENTS THROUGH TIMEChanges in lifeforms means a change in eon:
Cryptozoic- “hidden life”. No fossils- hadean, Achaean, protoerozoic.Hadean- Oldest rocks 3.8by. Young earth. Oceans made at end. Archaean- First life 3.8by Isua Greenland. Pillow lava shows oceans present. Stromatolites 3.45 bya North Pole Pilbara.Proterozoic- max stromatolites. Shallow seas good for stromatolites. BIF made. RODINIA supercontinent made 700mya. SNOWBALL EARTH- 3% Oxygen levels. Increase O when broke up. Ediacaran metazoans- visible life.Phanerozoic- “visible life”. More O. Cambrian- hard parts.
Fossil evidence for cyanobacteria exist in Aus in NorthPole Marble Bar Pilbara:
UV resistant. Make oxygen. Tolerate low oxygen and light. EVIDENCE OF FOSSILS: 3.45 bya in rocks PILBARA.
BIF require certain processes and conditions:
PROCESSES CONDITIONSCyanobacteria photosynthesis in top of ocean. Shallow waterIron oxide precipitates. High ironIron washed from rocks by acid rain into ocean. Acid rainBands of silica and iron occur when O builds up to kill cyanobacteria.
Anoxic atmosphere and oceans + high UV
DRAW DIAGRAM HERE:
Isotopes of carbon are evidence for life in 3.8.by rocks:
3 carbon isotopes. C14 unstable 5670 year half life. Plants like to take up C12 over C13. Observing ratio of C12:C13 in rocks can indicate whether
organic or not. ISUA GREENLAND ROCKS FIRST EVIDENCE OF LIFE C12:C13 organic material is 102:1 C12:C13 inorganic material is 100:1.
Fossilisation is rare due to breakdown and scavengers and lack of good conditions and needs certain conditions
Body fossils= once living things. Trace fossils= footprints, croptolites (poo). PROCESS- Dead organisms with hard parts buried in sediment e.g. storms over shallow seas disturb sediment, turbidites fossilise benthic organisms, floodplain sediment deposition, ash from volcanoes. Types of fossils:Petrification: skeletal material/shells in original form. CaCO3 preserved as calcite or aragonite.Carbonisation: soft parts converted to carbon rich residue e.g. plant fossils.Replacement: hard parts dissolved away and replaced with other thing e.g. CaCO3 with pyrite (FeS).Permineralisation: Minerals precipitate in internal organs/tissues. Blood vessels, vascular systems. Petrified wood.
Ozone and oxygen
3O2 ------ 2O3 can go the other away as well. UV breaks oxygen and one oxygen free radical joins to a spare oxygen molecule. Made 50km up in stratosphere. Ozone 2.5ppm stratosphere, 0.02ppm troposphere.
Cyanobacteria made oxygenated atmosphere:
Atmosphere is 20.9 % oxygen. The more oxygen made, the more ozone that gets made from the UV. First oxygen bonded in BIF. 1.8 by all Fe gone from ocean. Oxygen levels rose and diffused form ocean into atmosphere. In Phanerozoic oxygen reached stratosphere and ozone layer---- helped life onto land.
Ozone enabled life to move onto land as it filtered out the harmful UV.
Ozone filters 99% of UV. UV =mutagen. UV too high for life on land before ozone. 400-300 mya ozone high enough for land life in the PHANEROZOIC. Life previously restricted to ocean.
Stromatolites can’t live in most modern oceans because they have predators in them which eat them. Ancient oceans were more suited for them and their predators didn’t exist yet.
They are layeredd accretionary structures of sediments and cyanobacteria. Like harsh environs e.g. high saline, high temp, low oxygen. HAMELIN POOL SHARK BAY WA: water twice as saline as normal
ocean. Shallow pool with high evaporation, low oxygen and high temp. Grazing snails can’t survive there!
There were huge changes in life in the PHANEROZOIC:
Palaeozoic: animal phyla appeared, arthropods, amphibians, reptiles, life onto land, trilobites and brachiopods common, ferns rule land, reptiles ruled at end.Mesozoic: DINOSAURS, mammals and angiosperms ruled at end, conifers (gymnopserms) ruled, marine reptiles e.g. icthyosaurus, ammonites and belemites- marine cephalopods “squids with shells”.Caenozoic: Angiosperms and mammals ruled. Insects and angiosperms evolved together-mutualism – pollination by bees for example. ANALYSE: Mass extinctions drive changes in life forms and creation of new eras. New groups radiate out into vacant niches. Life onto land in Palaeozoic because of high oxygen and ozone. Eras end in mass extinctions.
You can find the relative age of a fossil from looking at a stratigraphic sequence:
Fossils won’t be found further up once disappeared from a rock layer. One disappears another appeared- faunal succession. Comparing when a fossil disappears in one layer to another is called CORRELATION. 3 IMPORTANT FEATURES OF STRATIGRAPHY: 1. Sedimentary rocks are layered horizontally. 2. Law of superposition- oldest on bottom- assuming no folding or faulting. 3. Layers of sedimentary rocks continue sideways until they get thin and disappear. IGNEOUS ROCKS ARE YOUNGER THAN ANY ROCK THEY CUT THROUGH. EXACT DATE ABSOLUTE DATING. NO FOSSILS IN IGNEOUS ROCKS.
Compare dating methods
Relative AbsoluteFossils Igneous rocks that cut through sedimentary
layers.Not exact dates Exact dateLaw of superposition Radiometric dating of daughter element ratio to
parent element. HALF LIVES.Shows changes and increasing complexity of life through time.
Uses comparison of known half-lives known elements
Organisms have evolved from past organisms:
Evidence: transition fossils e.g. archaeopteryx – reptile to bird, increasingly complexity of life, pentadactyl limbs, biogeographical evidence- radiated out from common ancestor, comparative embryology, biochem, many organisms only found as fossils.
Canberra fossils- Or, Si, De.
Ordovician- Canberra in deep water. Black mountain sandstone formed. Actin shale + Pittman Formation formed from subduction zone. FOSSILS- graptolites- floating colonial organisms.Silurian: Ground sinking, turbidites. Sedimentary basin submerged and volcanic activity occurred.
FOSSILS- corals- little bits, brachiopods- two shelled, gastropod- marine snail, trilobites-arthropods, crinoids- sea lilies.
Ediacaran fossils were soft bodied:
635-542 mya, Precambrian, evidence of increasingly complex life- frond/disk shaped plant globally distributed. Hard to classify metazoans as most lack mouth or anus, first multicellular, Kimberella had bilateral symmetry.
Living on land was hard to do but it had many advantages:
Advantages: more oxygen, more light for plants, new niches, more space to move around, less predators.Problems that needed to be adapted to: Getting and keeping water- desiccation/dehydration = death, oxygen is corrosive to cells- need to combat this, “Breathing” gas transfer was hard- lungs developed, Support- no buoyancy on land, became stiffer, temp varies lots on land, few salts on land-needed to survive, Pressure- high in water. Lungs developed because gills would collapse without pressure on land.
There were major steps in transition of life onto land:
PLANTS INSECTS VERTEBRATESLate Ordovician and Early Silurian- first non-vascular derived from green algae. Most low areas.
Only had xylem- no true roots or phloem. Sporangia. Stomates and cuticle. Moist low areas.Club moss an improvement on Cooksonia:
Had leaves and long stems. Sporangia-moist areas.
THE CAMBRIAN EXPLOSION
Hard parts are important because they explain the Cambrian explosion: Increase in oxygen enabled ozone-life to land.
Higher oxygen: bigger body size and energy usage, ozone- protect from UV, collagen could be made- structure for skeleton and muscle.Hard parts: protection from UV and predators, movement-muscles act off skeletons, Organ attachment- gills- get more O, animals can seal themselves from the world e.g. shells. Eyes- predators and food. Predator prey relationship- “Arms race” for best predator and defence drove evolution, all modern phyla appeared, PIKAIA- flat marine floating organism-had endoskeleton- uncommon- showing development of internal hard parts.Cambrian life forms were better than Ediacaran because they had protection, movement, organ attachment and pred/prey driving evolution:Higher O allowed exoskeleton development, hard pincers- Anomalocaris – good predator, good eyesight- eyes- see pred and prey.There were many changes in Cambrian life forms:New niches opened up- radiated out made new species, active hunting- go and get food!, sight, complex burrowing-OTTOIA, greater mobility and diversity, complex life, bilateral symmetry- better joint movement on both sides. ANOMALOCARIS: large 60cm arthropod, mouth and pincers grab food, good eye sight.OTTOIA: carnivore worm, 6cm, burrowed, ate carrion.
Riversleigh fossil site in QLD has a huge variety and number of fossils:
Fruit eating possum creatures, ancestral kangaroo Balbaroo fangaroo- carnivore, 35 species of ancestral bats-placental mammals.
Explosive evolution is fast following mass extinctions whereas gradual is slowly filling new niches:
Explosive- generalist species fill niches, rapid evolution, 50,000-100,000 years. PUNCTUATED EQUILIBRIUM.Gradual- Darwin and Wallace, took over 1 million years for organisms to specialise in niche and make new species . SLOW RADIATION INTO VACANT NICHES. Natural selection.
Mass extinctions is a large number of species from lots of niches all over world whereas small/regional is large no. species unique to an area:
Mass- >35% of species die. Many phyla die. Very quick-<2my. FollowsSmall- lots of species unique to an area die at same time e.g. Megafauna. Local climate change or a disease.
Permian extinction was the biggest eukaryotic life extinction ever:
95% marine organisms died, 80% terrestrial died. Pangaea formation. Lack of volcanics- cool planet- TECTONIC SUPERCYCLE- ocean currents and rainfall changed led to ICE AGE. MARINE REGRESSION- oceans into icebergs- benthic e.g. brachiopods, exposed on continental shelf. Specialists species die-some generalist survive by moving into deeper water. Exposed shelf rotted and oxidised- reduced ocean and atmosphere O levels increased CO2. ANOXIC OCEANS- destructive combination of
conditions. This killed deeper benthic organisms. Generalists moved into vacant niches “RADIATED OUT”. Pangaea broke up-ice melted due to higher temp from CO2 from Siberian Flood Basalt. MARINE TRANSREGRESSION- flooded shelf and killed terrestrial land that colonised exposed shelf.
Cretaceous/Tertiary K/T killed the dinosaurs:
BOLIDE- Chixulub crater Yacutan Peninsula Mexico 10km diameter dated at 65 mya. High levels of quartz crystals at crater- asteroid at high speed vaporised the rock and dispersed around area. Indicates major shock impact. Iridium is element common on asteroids- found in 65 mya sediment around world- came from big bolide. Disturbed sediment around world 65 mya evidence of tsunamis from bolide. Evidence of huge forest fires North America 65 mya from bolide impact. Tektites (droplets molten rock) found on Mexican Coast from huge impact.GRADUAL- many dinosaurs groups already dying off, angiosperms were taking over from gymnosperms which were dino food source- STARVE?, incomplete fossil record doesn’t show all dinosaurs and when they died- could have died at different times.
Megafauna extinction was either an iceage or human hunting:
CLIMATE CHANGE HUMAN HUNTINGFor Against For AgainstPlanet warmed and megafauna died because adapted to the cold. Fossils show megafauna died of drought stress.
Some megafauna fossils show some went extinct in ice age conditions ones they had previously survived
Aborigines were in Aus. 40,000-60,000 years ago and megafauna disapperared not long after.
No fossils of human and megafauna bones found together. Spiritual and cultural reasons made Aborigines hunt sustainably. Computer modelling showed that megafauna would have died in 1000 years if hunted hard by Aborigines. In reality took longer to die!
QLD fossils show extinction happened in 3 stages which links in with the climate change.
Some megafauna were already adapted to the cold e.g. Diprotdont
Megafauna weren’t used to predators and would have been targeted because they were big and slow with tiny brains.
Some megafauna survived to recent years 10,000-4,000 years.
There have been other megafauna extinctions e.g.New Zealand and Madagascar.Genyornis lived on Lake Eyre. Sediment shown that eggs in older layers that last ice ages.
Suggests humans killed them.
Conclusion: climate change most plausible, statistically you’d think human and megafauna bones would have been found together if they were hunted. Bones may have weathered away? Mix of hypothesis to blame.
Advances of life timeline DIAGRAM:
First organisms examples:
Name Features DistributionCooksonia (plant) Small- 15cm tall.
No leaves, sporangia, xylem, no roots, stomates and cuticle.
Hylonomus (reptile) 20cm long, small sharp teeth, ate insects
North America
There is a relationship between mass extinctions and geological time scale:
Palaeontologists found that particular organisms lived at the same time and also saw huge changes in the organisms found. Gave different names to periods of time before and after the big changes. They made proper boundaries through absolute dating. The boundaries of the changes coincided
with bolide or tectonic activity-mass extinctions. Punctuated equilibrium occurred after mass extinctions.
Caring for the countryAustralia has had a long period of low fertility:
Long period depletion of nutrient ions: Old soils 100my, no nutrients e.g. Nitrates as they are leached out.Stable continent: no active volcanoes, glaciation, uplift, so no soil rejuvenation from basaltic lava with trace elements in it. Glaciers grind rock--- soil. Himalayas active mountain building--- rich soils. East Coast more fertile soil due to more recent tectonic activity and bit of glaciation. Low Relief: no tall mountains with high rainfall- cloud condense, 10% Aus. has sufficient rainfall mountains, low rainfall=no vegetation and low organic matter, sporadic rainfall=severe erosion, no sedimentary plains with good soil because high mountains
There are many different causes of soil erosion in Aus:
Land clearing: increase wind erosion. SALTATION- soil particles bounce along. SOIL CREEP- soil rolls. DUST STORM- light particles airborne. Nutrients attached to small soil- wind erosion =low fertility!Solution: plant trees around crops, put mulch back on soil, take care NW slopes- hot winds, reduce machinery use- soil compaction, reduce stocking.Sheet erosion: runoff removes soil. Organic matter in topsoil lost.Solution: keep vegetation; reduce fallow periods, less stock.Rill and Gully: rill= 30cm, gully= 30m. Funnel water on land. High rain= erosion= soil loss= sedimentation waterways.Solution: more trees, less stock, no fallow, plant alongside drainage routes to hold soil together.Stream bank: erosion along banks of rivers, happens when trees are removed and stock walk on banks.Solution: reduce runoff- plough in contours along slope, no fallow, reduce stock getting to river, plant natives, dams and weirs.Urbanisation: hydrological pathways altered, permeability and soils cover reduced, high contamination, Catchment areas changed by houses, roads, carparks- water can’t get into soil =high run off. Topsoil loss. Less water recharge- concrete covers soil. Stormwater drains take water away- can’t get into soil to replenish water table, erosion occurs- weeds grow-salinity. Make management strategies-NSW water department laws say can’t cause soil erosion by building, councils now have to have sediment traps.Solution: hay bales trap sediment, silt traps in drains, roads and building sites (the green sheets of plastic near roads).
East coast has fertile basaltic soils compared to infertile lateritic soil in WA:
Soil fertility= high level of nutrients, moisture retention for plant growth.
Laterite BasalticHigh iron oxide from weathering Weathering of basalt mountainsNutrient poor- porous. Fine crystals-non porous
WA-old Achaean- no tectonic activity-nutrients leached.
Fertile
Highly weathered, sandy soil, light colours, duricrust, acidic, low in P and N.
Recent tectonic activity- Narooma subduction and glaciation.
No organic matter-no growth. High trace elements and mineralsLow trace elements. High fertility- growth- organic matter back in soil.
16% Aus fertile-mountains and river banks.Regions of natural salinity in Aus.include Lake Eyre, Northern South Aus and parts of Murray Darling Basin- Aus once inland sea:
Land clearing has very negative consequences including salinity:
Dryland salinity-remove trees. Evaporation leaves salt. Water table 2m from surfaceIrrigation: see diagramCONSEQUENCES- Will be 600% increase in salt affected areas unless prevented. Native plant species extinct with salinity. Adelaide will end up with saline water supply. Maquarie Marshes wetlands destroyed. Huge amount of money needed to fix crumbling roads and mortar in houses. Desertification. Loss of agriculture-no growth- no food or money. Population issue! Hard to feed if no food!Features of saline land: Salt erosion leaves no vegetation and eroded soils. Water table is high and soggy soil. Trees are dying and salt scalds on ground. Crumbling buildings and roads and very clear water-no algea!Solutions-Deep rooted trees in high recharge areas. Salt bush or Lucerne, pump salt water ont ponds, flush out rivers remove salt, restrict water usage, better irrigation methods.
Temora Farm had saline issues but fixed the problem by planting Lucerne:
Dry land salinity from land clearing. Loss of revenue since all crops died. Shallow root crops planted e.g. safflower and grass. In 1990s 0.4ha ruined with salty crust. Soil compaction also was bad. Biotic impact- weeds grew, toxic to stock, native plants died, native veg eating animals died no food.Abiotic- Soil salinity increase, “sodicity”- high Na levels made soil basic and caused to swell and break when wet into small particles which clog soil pores and increase run off, permeability increased and hard soils-erosion.How did they fix it? Lucerne-deep tap root planted 100ha away from salt scald, water table lowered –one year later they grew crops again, rain leached salt away, Lucerne=high water usage-long tap root access moisture deep in soil.SOURCE- Aus. Society of Agronomy.
Discuss- pesticides have very bad effect on everything: resistance occurs.
Insecticides, herbicides, fungicides. Combined effects of pesticides greater than all individual pesticides-SYNERGISTIC EFFECT. Chemical companies promote their products-sell to farmers! NON TARGET SPECIES EFFECTS- non specific to pests, disrupt food web-locusts killed and their pred birds die. OSPREY AND BALD EAGLE- THIN SHELLED EGGS CRACK NEAR EXTINCTION. DDT residual (chem stable). Fat soluble ones worse. Pesticides bond to aquatic sediments-make way through food chain.
Aerial spraying of pesticides means they spread out quick and wide and kill non target species. BIOACCUMULATION- fat soluble. BIOMAGNIFICATION- pesticide needs to be stable, able to move through food web, fat soluble. HUMAN EFFECTS- evidence of human illness from household pesticides- cancer, eye abnormalities, aging accelerated. Other pesticides cause abnormal sperm-can’t move, infertility, cancer, tiredness, limb pain, SUICIDAL TENDENCIES.
Alternatives to pesticides exist but there are problems as well as benefits from them:
Bio control:
Foreign organism to eat/control pest. FUNGAL SPORES sprayed from planes onto hopper phase locusts. 2-3 weeks to kill. Must observe properties all the time to check for locusts. 2-3 week to die is still long enough for crops to be eaten. Expensive and possibly dangerous- Non target and humans? Time consuming and need a pilot.
CACTOBLASTIS- moth ate prickly pear. Effective! Once all over Aus, not now. SUCCESS Need to do lots of research to see what organism will work/live in the area. Cane toads example of bio control gone wrong.
Natural insecticides:
Made form plants e.g. chrysanthemum. Called PYRETHOIDS. Fat soluble but will break down-not chem stable-wont bio mag/acc. PROBLEMS- is it toxic enough? May be hard and expensive to extract.
IPM:
Integrated approach to pest management. Avoid harvesting and planting in peak pest seasons Check before spraying instead of spraying before checking Don’t use pesticides if cost is greater than crop cost RESEARCH Redesign habitats to favour crop growth, make as natural as possible-permaculture. Multiple cropping- means just one pest won’t get massive quickly. Will take time Barriers- copper on trees stops slugs, flypaper, netting. Make a good environ for natural predators e.g. spiders Spray pheromones to attract pests to traps SUCCESS: Traps been good in Perth to trap
fruit flies. GM crops- need companion crops so resistance doesn’t occur rapidly. Bt Cotton.
SUCCESSFUL: kill Bollworm and increase cotton yield Lots of time, money and knowledge for IPM to be effective. Labour intensive. Multiple cropping is hard to harvest-different crops grow at different times. SUCCESS: USA IPM good in stopping a mite that carries bee pathogens from getting into
hives.
ASSES: all have great potential. Although expensive and time consuming they are much better for environ than pesticides. IPM and Bio control are only effective on small scale properties, not on big
farms. WAY TOO MUCH WORK ON BIG. PERHAPS A MIX OF PESTICIDES AND ALTERNATIVE METHODS WILL BE BEST.
DDT is a pesticide not in use anymore because it biomagnified and killed non target species:
DDT invented end WWII. Used to kill malaria mozzies in tropical areas to protect troops. Also used to spray Holocaust refuges to get rid of lice. In the 1950s and 60s it was widely used to kill insect pests on crops.Why stop using it? It is fat soluble and pushed the top of food chain e.g. bald eagle and osprey, nearly to extinction. Biomagnified and thinned the shells of the birds so that no babies could be born. Insect pests became resistant and super pests evolved. Banned since 1972 all across world except Africa and Asia where it is still used. DDT was sprayed in Borneo why WHO to kill malaria mosquitoes. Floors of BAYAK TRIBE collapsed because DDT killed wasps that ate the wood boring caterpillars that eat their thatch roofs. Outbreaks of typhus and plague occur because poisoned insects eaten by geckos----cats---- cats died and rats flourished. WHO parachute cats into Borneo to fix it. It’s residual chemicals are very harmful: DDT halflife 15 ears in water and breaks down to DDE also toxic. They bond to soil sediment and biomagnify through food chain. Disrupts food chain severely.
Soil compaction experiment:
Pore space in soil reduced, lower infiltration rate, lower gas exchange rate, roots can’t penetrate.Cause- raindrops, ploughing, heavy machinery, over stocking.Problems- increased run off occurs due to reduced infiltration rate (rate at which water goes into soil). Fertiliser and soil into waterways-eutrophication. Nutrient loss-topsoil gone.
AIM- to observe effect of soil compaction on soil features.MATERIALS- stopwatch, tincan (no base), beaker, pipette, measuring cylinder, electronic balance, Bunsen, filter paper, funnel, retort stand, ring clamp, evaporating basin, hammer (remove grass off soil), spoon, water bottle, incubator, trowel. SOIL SAMPLES FROM TRACKED AND NON TRACKED AREAS- Ag plot, oval, pathway.METHOD- PERMEABILITY: Tin can in soil deep enough so water can’t run out. 50ml water in tin and record time for all to soak in. FIELD CAPACITY (water holding): DIAGRAM. ORGANIC CONTENT: burn in crucible till no more glowing. Weigh before hand and after.CONTROL- same soil type, same sample sizes, identical methods used.VARIABLES: IV- soil compaction. D- permeability, organic content, field capacity. RESULTS: Direct link between soil compaction and soil characteristics. Everything is lower when tracked.
DISCUSSION: results significant to life as it shows how bad compaction is. There may be bias in organic content-worm in it. Permeability is subjective test- needs to be more scientific. Soil may not be uniform content and human error may stuff up results.
Greenhouse gases are bad and need strategies to stop their release:
GAS NATURAL ORIGIN MADMADE ORIGINCO2 Fires, respiration, volcanoes,
rotting.Fossil fuel burning, burn wood and waste, cement production.
SO2 Volcanoes, geothermal springs Fossil fuels, extracting met from sulfide ores. (cools planet down-aerosol).
NOx Lightning-high heat bonds N and O in atmosphere. Hot springs, bacteria release it from soil.
Fossil; fuels, high temp combustion chambers N and O combine. VERY GOOD ABSORBER OF INFRARED- WARM AND COOL WITH NITRIC ACID AEROSOL.
Combustion, steam from industry. WARM AND COOL- PROVIDES WATER FOR ACID RAIN.
STRATEGIES:
GLOBAL- emission taxes-carbon price, international treaties-force gov to reduce emissions, invest in cleaner fuels and renewable energy, fine big polluters, ration energy, sell fluorescent bulbs and ban incandescent.LOCAL- plant trees-subsidies, build bike paths and public transport, solar panels on houses- councils provide info on how to get set up, pay people to put wind farms on properties.
There are strategies used to assist the maintenance of natural water processes but there are often problems with them:
Environmental flow = min. water flow needed to maintain healthy river and marshland. Excessive water extraction leads to river and marshland damage. Low water levels---high
temp, high nutrients--- algal blooms--- DEATH. In past only consumption and usage of water was considered per river but now there is a
state wide monitoring and environ flows are being considered/ partially maintained. PROVIDING ENVIRON FLOWS FROM DAMS- SNOWY RIVER MOUNTAIN SCHEME: large
dams, pumping stations and hydroelectric system built Diverts water away from river and into Murray Darling Basin-reduced Snowy river flow to
1%. Gov promised 21%-28% flow rate but only 4% achieved because farmer lobby groups
convinced them to give more water to irrigation for Murray Darling. Occasional flushes occur to help get rid of sediment and build up in the river Reduced flow means the river is dying
Attempts to re-establish the flow rate have been held back by drought and agriculture needs.
REGULATED RIVER= most water given by gov to towns, houses-domestic. UNREGULATED- take as much water as you want but only in times of sufficient flow. LICENSING IRRIGATION/BORE WATER USERS: Flood irrigation- wasteful, flood the land, cheap. IMPROVE-capture all unused water and
reuse later, level field so no run off. Spray irrigation- fine mist. PROBLEMS- lots of runoff, wind carries water away, evaporation
in day (spray at night is better). WASTEFUL. Drip irrigation- expensive, labour intensive. Little drippers on all plants. Holes in drippers get
clogged and need to constantly maintain. LICENSING- sell licenses to farmers who want to use the river/bore water. Tradeable water
rights created by MURRAY DARLING BASIN AUTHORITY. WATER MANAGEMENT ACT 2001 lets the, keep 10% of rain that falls on their property. If
they need extra water its not necessarily give which is a good way to control water and land usage. People can tamper with their pumps and take more than allowed to.
Licensing bores controls the water table. Great artesian basin is still dropping rapidly because people take all they want from it.
TREATING STORMWATER: need to treat all to maintain quilailty fo fiver. Towns and cities have lots of pollution and this gets into river if not treated- dog poo, plastic, oil, chemicals. Filter out rubbish with traps.
Artificial wetlands- need a lot of land, aquatic plants filter out the nutrients so no algal blooms, microbes break down organic matter, remove the plants to remove the nutrients then plant again, removes solid and dissolved waste. Possibly only work in country areas with lots of land, cities may have to divert water there. Expensive to set up but pretty self sufficient.
Gross pollution traps- trap everything but not dissolved things, must clean and maintain a lot.
Oil and litter booms- floating barriers in water collect oil and litter.
Chemical reactions involved in making greenhouse gas and acid rain:
Hydrocarbon combustion- C + O + CO2 +H2O. methane from anaerobic breakdown and ruminant break down. ACID RAIN: S+O---SO2, SO2 + H2O--- H2SO3 (sulforous- oxygen can bond to make sulfuric), SO3 + H2O--- H2SO4. Nitrogen dioxide and water--- nitric and nitrous acid.Photochemical smog- UV and acidic gases—ozone and acidic gases.
Vehicle exhaust emission:
Hydrocarbons- unburnt fuels. Carcinogen.CO- incomplete combustion. React with OH free radicals. OH radicals break down greenhouse gases. CO=bad!Oxides of nitrogen- fossil fuel burning, high temp combustion. Sulfur oxides- fuel.Volatile organic compounds- non methane hydrocarbons eg.. organic acids and alcohol. Make ozone and pollute troposphere.Particulates- small solids block outgoing infrared and warm planet. BURN ETHANOL INSTEAD!
Different scientists have different views on global warming- anthropogenic or natural variations:
Most believe anthropogenic warming from fossil fuels, mining, agriculture etc. Others think temp rise is part of continual heating and cooling of climate due to natural variations.
ANTHROPOGENIC NATURALGHG conc. increased 280-395ppm since I.R. Greatly varying climate in earths past e.g. hot
carboniferous and Ice ages.Methane in swamps and clathrates (methane in sediments under seas) released with warming. Methane conc. doubled since IR. 20 x more effective at absorbing infrared than Carbon dioxide
Earths temp relates to natural CO2 levels from tectonic activity and respiration and Milkankovich cycles (earth orbit around sun)
NOx 300 x more effective infrared absorbed than carbon dioxide
All cycles should be having a cooling effect at the moment
Wild storms and heat waves more common. Planet has continually warmed since 20th Cent.We should be in a cold stage of the Earth’s natural variations but we are heating it!Warming is positive feedback ice melts, methane released, less albedo affect more IR absorbed.Studying ice cores we can determine past climate variations and CO2 levels. We can see that high CO2 = warm temp.
CFC’s were used as refrigerants, propellants, solvents in electronic circuits, dry cleaning, making plastics in 30s-80s.
Non-toxic, non-flammable, chem stable, CHEAP! Group 7 halides. Cl free radical. WRITE EQUATION SHOWING THE RECYCLING OF Cl RADICAL. One Cl can break down thousands of ozone. Bromoflourocarbon is a fire retardant used by fire-fighters- banned in most countries but atmospheric conc. increase til 1998.HCFC and HFC are replacements- break down to produce halogens but do so in troposphere-not bad.
Australian scientists Paul Frazer and Johnathan Banks helped find first ozone depletion evidence:
EVIDENCE- ozone depletion predicted in 1976 and confirmed 1980s by measuring ozone over Antarctica with a TOTAL OZONE SPECTROPHOTOMETER. Identified hole every spring. Hole over Antarctica due to wind patterns and earth’s rotation.Dr Paul Frazer- monitored ozone levels and campaigned to phase out CFC and recovered old CFCs.Dr Johnathan Banks- lobbied to include METHYLBROMIDE in Montreal protocol (fumigant kills soil fungus).
ASSESS: anthropogenic more likely due to all the evidence. If emissions not reduced, warming will be disastrous. Crazy storms, sea level rise, habitat destruction, ocean currents change, acidifying of oceans, crop failure-no food, extinctions, ice caps melt.
The 1997 Kyoto protocol has not been a success whereas 1987 Montreal Protocol has been:
KYOTO- GLOBAL WARMING MONTREAL- CFC160 countries signed. Forced them to cut emissions by 5.2% between 2008 and 2012
No CFCs made after 1995, phase out completely by 2000
There were clauses for developing nations e.g. China and India as we didn’t want to hamper their development
Hopes ozone recovery will occur by 2050
AUS and USA weren’t keen on treaty at time-fear would ruin economy. Aus now signed.
There were different clauses for developing nations e.g. China and India as we didn’t want to hamper their development
Aus emissions can increase annually y 8% 25 countries and majority of Europe signedUSA pulled out in 2001. They thought there should be carbon trading- buy carbon credits off countries not using them.
Later agreed to ban HCFC and phase out by 2030
Aus has made some moves to ratify it but won’t go anywhere with no carbon tax.EVALUTION- not successful, merely a way of gov looking like they’re combatting climate change, emissions continue to rise, half hearted approach to implementing strategies. Need stricter measures and more emission cuts for success
EVALUTION- very successful. Phasing out of CFC has occurred quicker than required due to cooperation by gov and industry. Replacements have been found and CFC emission slashed worldwide. Need to do more to ensure no black-market. Need to make sure developing nations abide by treaty.
Features of a rubbish dump include soil and rock type, landslide potential, tectonic stability, lack of groundwater and if they have bottom liners:
Soil and rock type: low porous rock and soil-stop leachate into groundwater. Uniform composition of rocks- no cracks or faults. IMPERVIOUS SOIL E.G. CLAYLandslide potential: need flat area. Landslides expose waste and release pollution.Stability: quakes fracture rocks leachate run off.Lack of groundwater: can carry leachate into rivers and gets pumped onto farms and drunk-toxic.Leachate: toxins, plastic, oil, pesticides, heavy metalsHDPE bottom liners: stop leachate. Always get holes, wombats burrow through, eroded by chemicals. ALTHOUGH WE CAN TRY TO STOP LEACHATE, IT WILL ALWAYS POLLUTE AREAS.
Methods to dispose, treat and recycle of solid and liquid waste- evaluate:
SOLID WASTE:Landfill: 97% solid waste to landfill, 3% to be treated. Need a lot of land-can’t do in cities. Transport is difficult and expensive-lots to move, expensive to dispose rubbish, maintain dumps is expensive, leachate is polluting-expensive damage. Need to treat hazardous waste e.g. biochem waste-incinerate or radiation to destroy. ALTERNATIVES- bioreactors- collect methane from breakdown of rubbish and burn to power homes. Lucas Heights Sydney.Recycling: Can recycle lots of things, can be done in factories in cities-good employment, recycle organic matter for mulch, recycle paper to make new paper. EVALUATION- big improvement in recycling methods. Need to be able to recycle everything in the future. Education: gov programs needed to tell people what they can recycle. Reduce excessive packaging. Reuse: incentives for
recycling e.g. 5c. Need to implement in NSWIncineration: burning. Banned-released carcinogenic dioxins into air.Liquid waste: usually toxic, transported and stored at dump and tested to see if toxic, add alum to flocculate, precipitate, put in centrifuge to remove solids, froth floatation-separate oil and then skim off, remove metals after everything and then can reuse the metals, neutralise acids bases and solvents-less harmful. EVALUATE- expensive, time consuming, dangerous to workers, use lots of power, need to get companies to reduce their liquid waste and make less toxic
Nabarlek Uranium Mine has been rehabilitated very effectively:
Get environment back to original conditions. HOW TO REHAB: fill mine with rock or soil, put topsoil back on land and stick to natural land contours and shapes, replant natives, native animals. AS OUR KNOWLEDGE OF ECOLOGY HAS INCREASED, COMPLEXITY AND EFFECTIVENESS OF METHODS HAS INCREASED.NABARLEK- Northern Territory operated 1979-1989 and had uranium extracted over 143 days and processed over 9 years. Waste was returned to mine pit.
Containing contaminated water-not let into rivers Neutralising tailings Minimising land to be cleared for mining Fill pit back up with soil and rock Landscaping and revegetating with natives ASSES: effective, ensuring that there was a set (enforceable by law) rehab plan before opening mine
let NT GOV decide if mine would be ok for environ. Mine now looks unchanged-lots of vegetation and the pit has been filed in. Ongoing mine site monitoring is occurring
Experiment: simulation of treating waste water.FILTRATION: pour murky water through a sieve and collect in a beaker. Observe how its cleanerFROTH FLOATATION:
PRECIPITATION: pour muddy water through a sieve into a beaker. Add alum and the particles will coagulate and sink. Add sodium carbonate and barium chloride to remove ions. The water will go milky then clear. SAFETY- don’t get waste water in eyes.
Experiment: show effectiveness of landfills
Landfills generate methane. Fill ¼ of milk bottle with food scraps and squeeze to remove air and put lid on. Leave in sun for 3 weeks swell with methane. Carefully puncture small hole in bottle and light a match and place over hole WILL BURN DUE TO METHANE.EFFECTIVENESS OF LANDFILLS: perhaps only solution we have to deal with non recyclable waste. Organic matter anaerobic breakdown methane and global warming. NEED TO IMPROVE METHODS OF LANDFILL TO REDUCE ORGANIC WASTE IN IT OR PUMP METHANE OUT TO POWER HOMES. Liquid waste is hard to deal with and expensive toxic by-products e.g. heavy metals. Can pollute environ. Better methods needed but expensive to change infrastructure.
OCEANOGRAPHYAverages of the ocean:
Feature About Changes with depthTemp 3.8 °C. varies with latitude and
depth –cold poles warm tropics.Sun heat surface-cold deep. Bottom is 2°. Tropics 32°. Poles 0°
Depth 3.75km Deepest Mariana trenchSalinity 35g/L 3.5% High salinity in subtropics and
dead sea and areas of high evaporation. Increases with depth. Low salinity around continents
Density 1.03g/cm3 Increase with increase NaCl. Decrease with temp
Earth covered by 71% oceans (361 million km 2) and they have huge effect on conditions:
More ocean in south hemisphere than north. Ocean moderates local and global climates. High heat capacity-keeps land warm-heat transported by currents. Currents create air and water circulation patterns. Carry heat away from tropics to poles and cold to tropics. Aus climate variability e.g. floods and droughts influence by Pacific Ocean. El Nino and Nina effect created by oceans- cool and warm currents change. El nino = drought in Aus and floods in Peru and vice versa. Ocean absorbs about half energy from sun reaching earth.
Origins of oceans are either outgassing or comet
Outgassing: young earth molten rock released water vapiour when cooling. Made clouds. Got below 100° and rained. Filled low areas oceans. Volcanoes release water as well.Comet: comet made od ice. Melt on collision. Lots of comets over time = lots if water. Not likely to be cause has low levels of DEUTERIUM in ocean but high on comets. evidence for age oceans: 3.95 bya sedimentary rocks show oceans made between 4.6 bya (earth formation) and 3.95 bya.
COMPARE: evolution of oceans vs atmosphere evolution.
Closely linked. First atmosphere made from outgassing from early vulcanism and left over gas form solar nebula- Hydrogen, Helium, CO2, methane water. Planet cooled rain. First rain acidic and leached out metallic ions first ocean acidic and ion rich. Photosynthesis (cyanobacteria) oxygenate ocean and atmosphere. Ozone made from oxygen. Salt came from dissolved salt in rivers from erosion of rocks. LINKED DUE TO C, WATER AND O CYCLES.
Ocean floor forms at MOR and destroyed at subduction zones.
Form: Red Sea.Subduct: active plate margins, convergence, pacific ring of fire.
Evidence used to date sea floor:
Sonar- depth. Oldest = deepest because cooler rock and denserPalaeomagnetic banding- magnetic crystal direction correlates with magnetic pole changesSediment dating- relative dating and core samples.Drilling: into basaltic seafloor absolute date K-Ar ratio.
Ocean is not more than 250 my old because it is continually being destroyed at subduction zone before 250my and recycled at MOR
Plate tectonics plays a major role in maintaining the 65-35% ratio of ocean to continent equilibrium:
Continent crust not subducted because lighter composition e.g. silica. Oceanic denser –mafic. Continent is thicker-super continent made by rifting and accretion of sediment via subduction. Oceanic continually subducted. Erosion of continents also occurs via water and wind.
Discuss: shifts in the equilibrium can have major impacts
Constant equilibrium-what’s changed is where land masses are. Variations in equilibrium caused by:
Sea level change: global warming- iceage. Last ice age and warming sea rose 170m. Isostatic changes- continents are buoyant and rise and sink-mountains are eroded, ice sheets
disappear from warming plate now less dense and floats Super continent break up.
Draw a diagram showing movement of carbon, water and O throughout ocean and atmosphere:
Experiment: compare solubilities of common salts
Materials: teaspoon, scales, large test tube, measuring cylinder, ice, Bunsen and tripod and gauze, stirrer thermometer.
Method: find out what one teaspoon of salt weighs. Stir in salt at low temp recording how many get dissolved in STIR ALWAYS till saturated. Heat up tube in 5° increments adding more spoons till saturation. Results: solubility all salts increased with temp. Most soluble was calcium chloride and magnesium chloride.Solubility rankings:
Attenuation of light: 100m is photic zone with phytoplankton-basis for foodchain. Depth penetrates. Green penetrates furthest-shortwave length. Darker as you go deeper.
Red and uv Orange Indigo Yellow Blue Green
Experiment- precipitation of salt in cooling solutions GET TEMPS
AIM-observe and predict which salts will precipitate out first in cooling solutionMATERIALS- salts, spoon, electronic balance, 500ml communal beaker, 150ml beaker, large test tube, beaker with ice, Bunsen tripod gauze, safety glasses, test tube holder, thermometer.METHOD- make solutions 10x seawater conc in 100ml hotwater stir and dissolve. Split solution into large test tube and 500ml beaker. Evaporate to half volume with Bunsen (don’t let it spurt out the top)and then put in ice bath (not too quickly so doesn’t crack glass. Record temp when precipitation occurs.
Salts in order of precipitating Temp at which precipitatedCalcium carbonateGypsumSodium sulfateMagnesium chlorideCalcium chloride
Depth
Brine shrimp hatching- effect of salinity and temp:
They live in lakes and waterways-crustaceans, eat phytoplankton. Tolerate varying salinities but die in freshwater. Eggs are dormant cysts.Variables: IV- temp and salinity D- number eggs hatchedControl- same ph light and container.Materials- brine shrimp eggs, specimen jars, binocular microscope, salt, electronic balance, fridge, incubator.Method:
1. Three temps: 2° fridge, 15° room temp, 30° incubator.2. Three salinities made using spoon beaker and electronic balance- o%, 1.5%, 3.5%.3. Eggs in equal amounts put in specimen jars- number that could fit in depression of a well in
microscope slide.4. Made 6 jars for each salinity. Put eggs in and then put in varying temps.5. 2 days later observed with microscope no. eggs after stirring 5 times to mix it up. Sucked up
with pipette and placed ion watch glass. Look with binocular microscope. Found average.
Results: direct link between salinity and hatch rate. Most hatched in marine conditions 1.5%. low hatch rate in freshwater. Only 2 hatched at 2°. 15° optimum temp for marine but 30° was optimum for fresh. No true correlation between temp and hatch rate. Most hatched in marine because that’s their natural environ. Discussion: need to improve counting methods to ensure accuracy and reliability.
Experiment: effect of SA:VOL on solids and rate of cooling
AIM- compare rates of cooling of different solids with varying SA:VOL.Materials- plaster of Paris magnesium sulfate, data logger, 3 probes, 800ml beaker with hot water, 3 500ml beaker with cold water.Method- make 3 spheres from plaster paris with radius of either 1,2,3cm and let dry. Leave in hot water until all temps spheres are the same-check with probe. Put spheres in identical beakers of cold water (make sure same temp) and use data logger to time their cooling rates. Graph results on computer. Results- 3cm had highest SA:VOL ratio and took longest to lose heat. Smaller ones lost heat more quickly. Need to repeat with more spheres of different volumes. No controls uses as results based on comparison.
