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Module 1: Earth's Resources Structure of the Earth, the Early Geosphere, Atmosphere and Hydrosphere
● investigate and model the processes that formed the geosphere (ACSES018), atmosphere (ACSES022) and hydrosphere (ACSES023)
● investigate the evidence for the structure of the Earth using technologies, including:
− seismic wave velocities Analysis of seismic body waves (which travel through the Earth) provides evidence of Earth’s layers
How its works Change velocity (speed in a given direction) as they reflect (bounce) and refract (bend) through different substances of differing densities Move from the epicentre of the earthquake Evidence showed through seismic wave velocities
1. We know that density and pressure increase with depth because wave velocity increases with depth (waves travel faster through denser material)
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Geosphere Atmosphere Hydrosphere
The geosphere is composed of all the material below the solid surface of the earth. It consists of the silicate rocky crust and mantle, as well as the metallic core. The geosphere was formed due to accretion formation of the earth.
The atmosphere includes all the gases on the Earth. The molten rocks of the young, hot Earth released a mixture of gases. This process is outgassing. The atmosphere was mainly anoxic, meaning it had no free oxygen.
Origins not fully known! Icy asteroids hitting the Earth's surface → releasing H²O. Volcanic outgassing: surface molten, covered in volcanic eruptions. The surface cools and water vapour condensed and falls to the ground. Rain falls for centuries, oceans and forms where the areas are low lying.
P – waves (Primary) compressed longitudinal waves → can travel through solids and liquids (slower travelling through liquids due to atoms being less packed)
- Waves travelling at an angle are progressively refracted as they encounter materials of increasing density - Waves perpendicular are unaffected and travel in a straight direction
S – waves (Secondary) transverse waves → can only travel through solids
- Where waves don’t reach are known as shadow zones. S waves have a larger shadow zone compared to P waves as the cannot go through liquids
2. At the boundary between the mantle and the core (~2900km), S waves are stopped and P waves slow down. (meaning the outer core is liquid!)
3. A surge in the velocity of P waves is felt at a depth of 5100km indicating that the inner core is solid!
− meteorite evidence to demonstrate differences in density and composition Asteroids and comets are together classified as meteoroids.If any of these enter the Earth’s atmosphere they become a meteor, and once they reach the Earth’s surface, they are called a meteorite. Meteorites are solid pieces of material that have reached Earth’s surface. They have more Iron, nickel and iridium (denser than most surface rocks) Most are remains of asteroids, planetesimals, moons, comets that collided and disintegrated during accretion phase of formation of the solar system Evidence showed through meteorites
1. Meteorites were made from same ingredients at the same time as Earth (therefore elements found in these meteorites should be found in Earth)
2. They also haven’t been subjected to rock cycle or weathering and erosion 3. Many meteorites are DENSER than the crust (contain heavy metals iron, nickel and iridium) 4. The inference can be made that these dense materials found in iron meteorites were present during Early earth but
melting and differentiation caused them to sink out of sight into Earth’s interior (core)
● describe the compositional layers and thickness of the Earth’s layers, including: − lithosphere
○ Brittle, outer layer shell of the geosphere ○ SOLID REGION → Consists of crust and upper mantle ○ The average thickness is ~70km but ranges widely
− Asthenosphere
○ viscous, (plastic liquid-like), ○ weak and constantly reforming → convection currents (13000°C) ○ It is about 100km thick
− crust, mantle and core and their compositional layers
Crust
Mantle
2900km thick, mainly made of olivine and peridotite 1. Upper Mantle: solid part (lithosphere) (1000°C) 2. Asthenosphere: viscous, (plastic liquid-like), weak and constantly reforming → convection currents (13000°C) 3. Mesosphere: semi-fluid, the boundary between mantle and core (3700°C)
Core
● analyse evidence of the Earth’s age, including: Isotopes Isotopes are elements with the same number of protons but different numbers of
neutrons. They have a different mass but do have the same chemical properties
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Factor Continental Oceanic
Thickness Average 50-60km Only 5-8 km
Typical rock Granite Basalt
Age Often billions of years old Rarely more than 200 mill years old
Factor Outer core Inner core
State of Matter Liquid Solid
Thickness 2300 km 1220km
Temperature 4400°C 5500°C
Composition 80% iron and nickel
- Protons + electrons = mass number - Mass number - protons = neutrons Radiometric Dating Radiometric dating is the most reliable evidence for the Earth’s age. It is a method of dating geological samples by analysing
the proportions of particular isotopes - In some isotopes the nucleus is unstable and will decay into a different stable atom - The original unstable atom is the parent - The new form of stable atom is the daughter - Analysis of a rock sample where the ratio of an unstable parent atom is compared to a stable daughter atom helps
determine the age of the rock sample Half Life - A half life is the time needed for ½ of the parent radioactive atoms to decay into the daughters atoms Zircon Crystals In 2001, a zircon crystal was extracted from a rock in Jack Hills, Western Australia. The mineral is highly resistant and present everywhere. It can withstand conditions like high temperatures and chemical weathering! The crystal contains radioisotope uranium which has an incredibly long half life of around 4.5 billion years. These crystals were found to be the oldest rocks in the earth. This allows us to efficiently date rocks even older than the earth itself. Through the zircon crystals we can determine that the planet was wet and cooled quickly (big collision theory). We also learn that solid rock and liquid water was on earth 165 million years after the solar system was formed. Scientists analysed using the mineral using microbes- radioisotopes dating where basically they looked at the uranium (parent) in it and compared it to the amount of lead (daughter).
Meteorite evidence - They are not exposed to weathering or plate tectonics, thus a perfect snapshot into early days of formation of our solar
system - Ages have been calculated using radiometric dating and indicate age 4.4-4.57 billion years old . This confirms the
predicted age of the Earth Rocks, Minerals and the Rock Cycle
● investigate the chemical composition of a variety of minerals and explain their formation, including Minerals are naturally occurring compounds, usually with a crystalline form and formed by geological processes. They are naturally occurring inorganic structures that have a distinct chemical compound and structure. Silicate minerals are the most common form of mineral. They are broken into two groups, felsic and mafic minerals.
● investigate the physical properties of minerals that are used to assist in classification
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Felsic minerals Mafic minerals
- Relatively richer in silicates - Less dense - They tend to be lighter in colour
Example: quartz, feldspar
- Rich in magnesium and iron but relatively low in silicate
- Much darker in colour (green-black) - More dense - Common in oceanic crust
Example: olivine
Hardness Hardness is the resistance is to being scratched. Each substance falls between 0-10 on Mohs Hardness scale.
Colour streak Streak refers to the observable colour when powered. Streak is the lone left by a rock after dragging it across a white tile. Colour is not the most reliable of properties as minerals can exhibit a range of colours
Lustre Lustre refers to the shininess of a mineral's surface (or appearance of light as it is reflected off surfaces). Identifies a mineral is metallic (shiny) or nonmetallic (dull) Vitreous (glassy), perealy or earthy (dull)
Cleavage and fracture Cleavage is when minerals breaks along a flat surface or into sheets Fracture is when a mineral breaks with lots of jagged edges.
● explain the formation of rocks as characteristic assemblages of mineral crystals or grains that are formed through igneous, sedimentary and metamorphic processes, as part of the Rock Cycle
Igneous Rocks - Categorised by their crystal texture and chemical compositions - Formed through cooling of molten activity (lava or magma) - Igneous rocks are the best for radiometric dating because when igneous rocks cool and mineral harden is when
radiometric dating begins Depending on where and speed at which rocks cool determines crystal size:
- lava/magma cools QUICKLY→ SMALL fine crystals (eg basalt) - lava/magma cools MEDIUM→ MEDIUM sized crystals - lava/magma cools SLOWLY (as in under the crust)→ LARGE crystals will form (eg granite)
Igneous rocks that solidify underground slowly (intrusive) are referred to as plutonic and form larger, coarse crystals Those that cool on the surface quickly by exposure to air or water (extrusive) are referred to as pyroclastic and form small, fine crystals. Sedimentary Rocks
- Sedimentary rocks form in layers called strata They are formed from weathering of particles when they are compacted and cemented
- They are divided into subgroups: clastic chemical and organic depending on the conditions under which they were formed.
Metamorphic Rocks These are the result of existing rocks being changed by heat and or pressure so they have a totally new form. There are 2 types determined by the manner they were formed: Contact metamorphic rocks have been altered primarily by heat from close contact with igneous solution (eg molten rock) These are found in bands around the intrusion. * non foliated and occur at a much smaller scale Regional metamorphic rocks are those that have been altered primarily by high pressures when tectonic plates collide causing these rocks to form * foliated and occur and a much larger scale Foliation refers to the layering within metamorphic rocks. The Rock Cycle The rock cycle states that any rock type can be changed into any of the other two rock types and back again through the Rock Cycle
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Specific gravity Specific gravity describes a minerals density compared to water ensity d = mass volume
Specific properties Some minerals have other specific properties that can be used for identification, For example: calcium carbonate will bubble if acid is dropped on it, magnetite is magnetic, others fluoresce in different colours under UV light.
Clastic sedimentary rocks are formed from weathering and eroded pieces of other rock that have been cemented together They are classified by size
○ conglomerates→ cemented pebbles (large pieces) formed from high energy transport
○ sandstone→ sand grains formed from intermediate energy transport
○ siltstones→ fine grained sediments formed from low energy transport
Chemical sedimentary rocks are formed by chemical precipitation which occurs when the evaporation of water from shallow water bodies causes the water to become saturated with soluble minerals. Some examples are halite and gypsum.
Organic sedimentary rocks are composed of materials found by biological processes e.g. dead organic/ once living materials. Some examples are coal and fossiliferous limestone.
● explain the formation of soil in terms of the interaction of atmospheric, geologic, hydrologic and biotic processes Soil is a mixture of organic and inorganic matter and provides a medium which allows abiotic (non living) and biotic (living) organisms to occur. Soil is made from weathered minerals particles, organic matter, water, dissolved gases and living organisms. Regolith → place where biosphere interacts with physical spheres Pedosphere→ the pedosphere is the outermost layer of the crust that is composed of soil and its formation. The depth varies from nonexistent to tens of meters. Soil Horizon→ The soil horizons are the layers of soil parallel to the surface (different horizons will have different chemical compositions) Soil profile→ Soil profile us the overall arrangement of these different layers Leaching→ leaching occurs when water washes away soluble (dissolves in water) substances from the soil, often to the layers below. This can be good or bad. Illuviation→ illuviation is the movement of silts and clays to lower layers Eluviation→ illuviation is the removal of materials from soil layers via leaching or illuviation Factors Affecting Soil Formation 1. Bedrock The base inorganic (non living) component comes from bedrock that is weathered and broken down to form grains of soil. If rocks are more resistant to weathering, soils will be thin and easily weathered they will be thicker 2. Climate Contributes to the formation and fertility of soil by causing weathering of material and encouraging biological processes 3. Topography Topography of landscape refers to the slopes and hills of the land. Comparing soil from slope to flat land shows how this affects them 4. Water Movement
- Horizontal waters such as rivers and shore lines cause weathering of soils and rock - Vertical water (running) causes eluviation of soluble materials from upper horizons of the soil, the raising of water tables
can bring these substances back up to the surface, alerting the chemistry of topsoil 5. Time Weathering, erosion, deposition of materials, accumulation of biomass AND the formation of horizons can take 100s to 1000s of years Soil Horizon O horizon → “organic” loose and partly decayed organic matter A horizon→ is the most important layer for life, it consists of lots of human and intense biological activities hence why it is darker in colour E horizon→ is located in between A and B and is ‘eluved’ zone of leaching and is very pale because lack of nutrients B horizon→ called subsoil and has less organic activity and contains the most leached materials C horizon→ known as subtraction which consists of weathered rock and little organic activity R horizon→ is bedrock and tend to be the base material for above layers Geological time scale
● describe relative and absolute dating of the geosphere Relative Dating - the science of determining the relative order of past events (i.e., the age of an object in comparison to another), without necessarily determining its absolute age (i.e. estimated age)
- Strata’ = sedimentary rock that are formed in layers
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Absolute Dating - the measurement of the actual age of something, in years.
- Materials are able to be accurately dated by examining radioactive isotopes (radioisotopes) - Radioisotopes are atoms with unstable nuclei that emit energy in the form of radiation and transform into other atoms at
predictable rates. - As each (equal) half-life of time goes by, half of the previous sample of
atoms decays. Compared to the original starting sample, the amount remaining is a fraction as shown.
Geological Resources
● investigate traditional Aboriginal quarrying and mining methods - Relied on stone tools to assist with hunting, gathering and processing of food and medicines. - Stone tools were created at ‘quarry sites’ (open pit mines where particular stones of value were available) - Usually rocky outcrops with rocks exposed by erosion were ideal - Example Mount William stone quarry and Narcoonowie grindstone quarry (grindstones were used to grind and crush
different materials.
● locate and relate a range of non-renewable resources to their location Resources is anything supplied by earth to satisfy a particular need of humans or other living things e.g food water minerals
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Law 1: Law of Superposition
In an undisturbed sequence of rocks, oldest rocks are on the bottom. Youngest are on the top
Law 2: Law of original horizontality
When it is first deposited, sediment is always laid down in horizontal layers (due to gravity), HOWEVER these layers can be bent by geological activities.
Law 3: Law of lateral continuity
Law of lateral continuity states that layers of sediment are deposited as continuous layers that extend laterally (horizontally) until they reach a boundary or are exposed to erosion after deposition took place.
Law 4: Law of cross-cutting relationships
Any feature that cuts across a sequence of rocks, is younger than everything it cuts. ‘the unbroken surface is younger’ Intrusion = When magma forces its way through cracks in other rocks we call this an intrusion. It may solidify to form a dyke (vertical) or sills (horizontal)
Law 5: Law of inclusions Any rock or fragment that is included in another rock is older than the rock in which it is included
A renewable resource can be replaced by natural resources - takes less time than 80 years - examples; air water, sunlight new sentence
Non-Renewable resources are natural resources that cannot be remade or regrown at a scale comparable to it's consumption Minerals
- mineral deposits = higher concentration of minerals - economically viable deposits = mineral ores
Fossil Fuels
- Materials that have formed as a result of past biological and geological processes - Once living things have been converted by heat and pressure over long periods of time - Release energy and carbon dioxide when burnt
Source Rocks → rock that contains sufficient organic material to create hydrocarbons when subjected to heat and pressure overtime. Components involved in formation of Petroleum traps. (i) Source Rocks (ii) Reservoir Rocks (iii) Cap rocks. Oil and gas accumulation 1. Crude oil forms in the source rock as it is buried and the
temperature and pressure results in changes in the hydrocarbons molecules.
2. As it forms its density changes and it will migrate through the pores on the source rock.
3. It will continue to migrate until it hits an impermeable rock - the cap rock (impermeable → no gaps for oil or gas to see through.
4. There it will accumulate in the reservoir rock (sandstone → high porosity= more oil = more economic value) until the source rock is exhausted.
5. Natural gas can also be formed through this process. As it's density is less than oil it will displace the oil underneath the caprock.
Economically sufficient Ore
- A resource is economically viable if the cost of mining is less than the price received by profit. - Legal and environmental considerations which need to also be made. - Finding new economically viable deposits has become increasingly challenging due to the high demand globally.
Factors affecting economic viability
1. Grade (amount)
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Coal Petroleum Natural Gas
- Produced from thick vegetation in sedimentary basins over millions of years
- Heat and pressure drive off much of the water
- Increasing carbon content = “coalification’
- How much water is present will determine the rank of the coal (high quality = no water) peat = lowest rank, anthracite - highest rank
- Used extensively for production of electricity
- Liquid hydrocarbons forms by chemical and heat alterations of buried Marines organic matter ‘foraminifera’ (organism like zooplankton) in marine sedimentary basins
- Heated by either igneous intrusions or release of heat from the mantle over long periods of time.
- Crude oil = unrefined Petroleum.
- Predominantly used for transportation of fluids.
- Closed association with Petroleum → formed in marine basins but just exposed to higher heat / pressure when caused organisms to further decompose into gas.
- Combustible hydrocarbons gases (mainly methane).
- Coal steam gas → primarily methane found in coal deposits.
- Natural gas → occurs in association with crude oil.
2. Size of deposit 3. Easy access to infrastructure 4. Current and projected price of commodity 5. Demand both locally and globally.
Metallic v non metallic ores. Metallic deposits of ores = iron, gold, silver and aluminium Non-metallic deposits of ores = sandstone, limestone, diamond, coal, Petroleum and natural gas.
● analyse the economic importance of Australia’s non-renewable resources (ACSES061) - Provides income for the government. - Depends on resources that mining provides us access to. - Provides rural communities with infrastructure transport and schools. - Supplied 251 700 people with employment in 2018
● investigate and assess the appropriateness of direct sampling techniques and remote sensing techniques in discovering non-renewable resources Remote sensing = gathering of information from a distance. Direct sampling = gathering a piece of Rock / soil in the field
● investigate the locations and extraction methods of, for example: (access 074) Surface mining
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Satellite image - Cost effective way of determining areas which have a high likelihood of containing desired resources (can be used for 20 years)
- Sensors record radiation reflected of earth's surface - Different objects reflect / refract and absorb light differently depending on chemical and
physical properties. - Converted into images by specialist software by geologists so it can be analysed. - Provides geologists the location of tracks, roads, fences and inhabited areas. - This is important for mapping out potential access corridors for exploration areas and
considering the environmental impacts of large projects.
Aerial photographs - Taking photos of air → allow mapping to be done rapidly and much faster than on ground material (ie identification of heels, services surface rock types ect.)
- geological features could be examined and later identified. - Helpful when deciding where they might send a team on the ground.
Geophysical data - Geophysics → physical characteristics of rocks (density, radioactivity). - Airborne geophysics surveys use a magnetometer to measure magnetic intensity. - Gravity surveys using gravimeters → help identify areas of Mineral deposits as different
densities will have different ‘gravity signatures.’
Seismic methods - Required small explosives charges open (ie air gun) being detonated and then studying shockwaves.
- Reflections of shock waves provide information about stratigraphy and structure of sedimentary basins.
Geochemical data (direct sampling)
- Stream sediment sampling → river sediments analysed for particular metals. - Soil sampling → representative of site conditions. Can be used to quickly establish the
existence and extent of hoped-for mineralization. - Drilling → gathering of underground samples to assess whether design materials resource
is present.
Open pit mining - Excavation made in ground surface (which remains open) overburden is removed to spoil banks and is then or is broken up with explosives (been refined).
- A bench is a large ledge that forms a single level of operation for which mining is occurring. Several benches may be operational simultaneously.
- Allows for work to occur on a massive scale using large trucks. - This makes it possible to mine lower grade deposits that otherwise would not be mindful of
stopping use to mine coal near-surface and copper, iron, aluminium and gold.
What impacts does surface mining have?
- Changes land topography and drainage - Strips land of vegetation, soil and rocks - Spoil banks erode and weather away - Rainfall leaches toxic chemicals into soil profiles
Underground methods
What impacts does underground mining have?
- Less waste than open pit mining however far more dangerous - Workers die in mine collapses, water dissolves toxic chemicals in mine, explosions in old tunnels are not uncommon due
to natural gas igniting easily
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Strip mining - Strip mining is the process of mining a seam of mineral by removing a long strip of overlying soil and rock. Strip mining is a practical when the ore body that is to be extracted is very near the surface.
Mountaintop mining
- Mountaintop removal requires explosives to blast debris off mountain tops in order to reach coal seams deep inside the earth,
Room and pillar method
- Typically coal, iron and copper - Carried out IN the ore deposit by an electrically powered machine which gathers coal then
dumps into shuttle cars to conveyor to transport out of mine - May occur hundreds of metres below ground surface - A series of ‘rooms’ are mined which leaves ‘pillars’ of the ore remaining which support the roof
(this must be very carefully calculated as otherwise ‘rooms’ risk collapse!) - Considered slightly more ecologically friendly as surface is preserved above
Longwall method
- Coal mining ‘long’, horizontal ‘wall’ of ore is excavated from one of its faces using a longwall shearing machine
- Large panel up to 350 m long and 4 metres thick - Massive shearers cut coal from a wall face, which falls onto a conveyor belt for removal. - Artificial support is provided to the excavated space (stope). These supports are gradually
pulled out as excavation proceeds, so that the overlying rock collapses from the farthest side of the miners.
- The coal is collected on a conveyor and transported to the mine’s processing facilities.
Sub-level stoping
- Hard-rock ore is removed by drilling/blasting a hole or ‘stope’ - A series of horizontal tunnels, or sub-levels, are excavated one above the other, to access
different levels of a vertical ore deposit. - At the bottom of the stope is a haulage tunnel, which is used to transport ore that collects at the
bottom.
Cut and fill - Used when ore body is found in steeply dipping rock with low strength - Mining is carried out in horizontal slices along the ore body, where the bottom slice is mined
first. - The slice is then backfilled and the fill becomes the working platform from which the next level
is mined.
Onshore and offshore drilling Use of petroleum and natural gas
- Petroleum and natural gas are trapped in porous rocks DEEP under Earth’s surface and are extracted using drilling methods (offshore and onshore)
- Petroleum and natural gas products are used widely in our everyday lives (we are very dependent on them both as a society!)
- Petroleum products are used for making plastics, transportation of vehicles, fertilisers, pesticides, waxes, tar, chemicals, synthetic materials like nylon, beauty products, medical supplies etc!
- Natural gas products are used for generating electricity, cooking, heating and cooling our ‘houses and water Extractions of petroleum and natural gas Onshore drilling: deep holes are drilled under the earth’s surface Offshore drilling: drilling underneath the seabed In general the equipment for onshore and offshore drilling is similar (tools like waste-water/oil separators, pumps, pipelines and storage tanks for petroleum/natural gas Onshore drilling
1. First hole is vertical (surface hole approx. 30 metres) using a drill bit and then steel casing is then cemented in place to stabilise ground
2. ‘Drilling mud’ is sent down in hole to maintain pressure and keep drill bit cool 3. Once desired depth is reached, drill pipe is removed, and hole is reinforced with
cement 4. After this, a specialised drilling motor can be attached and sent down which
enables drilling of curved/horizontal sections of well at much greater depths 5. A perforating gun is lowered into the deepest part of the well and fired which
creates holes that connect the rock holding the oil and natural gas to the well 6. ‘Fracking fluid’ (99.5% water and sand, 0.5% chemicals) is pumped at high pressure
through perforating holes. This creates cracks in the rock and frees up the oil and gas inside the reservoir rock → oil and gas flow up through pipe where they are processed at the top
Offshore drilling
1. Drill bit and large metal case pipe (which surrounds drill bit) is lowered to the seafloor and forced beneath seabed
2. High pressure ‘drilling mud’ is sent to drill a bit and then moves back up to the platform. IMPORTANT for lubricating the drill bit, maintaining suitable pressure and carrying rock pieces away from the well.
3. Once drill bit reaches appropriate depth, it is retracted back to surface 4. Smaller metal casing is then sent down into the well and secured. 5. Blow Out Preventer (BOP) is placed on top of the well to maintain a safe
pressure. It is connected to the drilling rig by a ’marine riser’ which allows oil and gas to travel back to surface
Offshore drilling environmental challenges:
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- As easily accessible oil and gas resources became depleted, and technology improved, the oil and gas industry have expanded into deeper waters in recent decades
- However, this deep-water expansion has not always been matched by legislation that reflects modern practices of environmental conservation
Module 2 : Plate Tectonics Evidence for the Theory of Plate Tectonics
● analyse evidence, including data and models, that supports the theory of plate tectonics, including but not limited to: the ‘jigsaw fit’ of the continental shelves The theory of jigsaw fit is the idea that if you were to slide the continents toward each other they would almost make a perfect jigsaw fit. This theory supports that our continents were once all joined as a supercontinent called pangaea. Wegner noticed that Earth's continents looked as if they were pieces of a puzzle. In 1912 he took this idea and proposed the theory of continental drift. This theory suggested that Earth's continents were once formed as a single landmass called Pangea. This theory was suggested by Alfred Wegener but his ideas were originally rejected. Matching up identical fossils on different continents Index fossil locations of organisms match across distant continents and are also consistent with the “jigsaw fit” model of plate tectonics evidence. Since the oceanic distance was too far for them to have travelled on their own, this supports Wegener’s idea that the continents were once joined as a supercontinent For example, the cynognathus was a mammal like reptile, found in south america and africa. However this mammal was not capable of migrating across the atlantic ocean as it was a land dominant species. This supports Wegener’s idea that the continents were once joined as a supercontinent. Holmes was intrigued by Wegner’s theory and wanted to find an explanation. In 1928 he proposed that Earth's continents move over time as a result of convection currents within the mantle. His model explained how magma rising to the crust formed mountain ranges. the profile of the ocean floor Bathymetry= Study of seafloor Bathymetric maps= map of the seafloor In the 1960s it became possible to map the seafloor with sonar, a technology originally developed for spotting submarines for the Cold War. The map revealed mountain ranges and trenches at plate boundaries in predicted locations, consistent with the theory of plate tectonics. Harry Hess noticed the relationship between the mid-Atlantic Ridge system and oceanic trenches. Using Holmes theory he proposed that convection in the earth mantle creates the seafloor at mid-ocean ridges. Rising currents would have caused the continents to split and drift. – the age of seafloor rocks New crust is continuously formed at the mid-ocean ridges as they move apart from each other. As the rocks produced at the ridges are igneous basalt and gabbro, it gives scientists absolute dates of their formation. We can predict that rocks will become progressively older as they move away from the mid-ocean-ridges. Taking samples from across the ocean floor gives exactly this information; the rocks near the continents are predictably older than the newly formed rocks near the ridge Glomar Challenger was a research ship which drilled below the seafloor and collected sediment and rocks. They were able to prove that ages of Basalt match the sea for magnetic stripe ages. This further provided evidence that the seafloor was formed at mid-ocean Ridges and the age of sediment increased with distance from the ridge. – magnetic reversals and seafloor rocks Magnetic reversals are preserved in the rock of the ocean floor through the process of seafloor spreading. As new magma reaches the surface and cools, the lava contains little magnetic minerals that align with the Earth's magnetic field at the time of its cooling. As such the ocean floor consists of alternating polarity of rocks and preserving the earth's magnetic reversals. Geologists Matthews and Vine discovered that every few million years Earth’s magnetic field reverses its polarity, this is called
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magnetic reversal. The patterns on either side of a ridge are symmetrical- rocks at a particular distance from the ridge on one side always have magnetic fields pointing in the same direction as the rocks the same distance on the other side. The stripes are symmetrical on either side of the mid-ocean ridge (i.e. at equal distances on either side of the mid-ocean ridge the polarity of the rock is EXACTLY the same, meaning that these rocks were once closer together however have since been pushed apart by seafloor spreading).
Plate Boundaries
● use geological maps of the Earth to locate boundary types and model the processes that have contributed to their formation, including:
Normal, Reverse and Transform Faults
– divergent boundaries
Volcanic and Earthquake activity:
- Divergent boundaries have few and weak, shallow focus earthquakes (as there is no subduction zone)
- Volcanic activity at divergent boundaries is effusive eruptions, with mafic magma, low viscosity, allowing a steady flow of magma. These characteristics result in an effusive eruption.
- Shallows earthquakes Rock types:
- distinct rock types at divergent boundaries are dark mafic gabbro (intrusive-coarse grained) and basalt (extrusive- fine grained).
- At mid-ocean ridges, basalt solidifies as pillow lava rocks. They have a distinct shape and give a history of that section of the crust, especially when found on land.
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Fault Force Hanging Wall
Plate Boundary
Example Image
Normal Tension (Folding)
Down Divergent Mid Atlantic Ridge
Reverse Compressional
Up Convergent Indonesia
Transform Shear
N/A Transform San Andreas Fault
Oceanic-Oceanic Continental-Continental
At divergent plate margins, plates are moving apart and a new lithosphere is being created. In the oceans, this has produced the mid ocean ridge system.
At divergent plate margins, plates are moving apart. Within continents, divergent margins produce rift valleys
Mid Ocean Ridge
- Ridge system forms linear mountain chain - The ridge crest sits 2-3km higher than the deep seafloor ocean basins surrounding it - Mid ocean ridge is most common of divergent boundary types
Rift Valleys (continental-continental boundaries diverge)
- Divergent boundaries on continental boundaries form rift valleys, a linear shaped lowland between two or more highlands.
- They are formed by the two diverging plates extending and the land between them thinning and sinking to form a valley.
- They can also be identified by normal fault lines. – convergent boundaries
Earthquakes:
- They occur where the subducting plate drags against the crust and mantle. (Enormous friction is occurring here)
- An earthquakes ‘focus’ is the point where the rocks suddenly break/move during earthquake
- Shallow focus earthquakes result from movement along fault lines within folded mountain ranges
- Deep focus earthquakes are caused from friction of descending plate with overriding plate
Volcanic activity: A key feature of the magma is that it is rich in SILICA. Silica comes from the sediment pulled into the mantle and melted on the subducting plate OR from melting of continental plate as rising magma forces its way up. The magma is felsic – its higher silica content makes it more viscous than that of effusive volcanoes at divergent boundaries. This means there are more dissolved gases trapped and the eruptions are more violent and lava flows more irregular and spluttery, and hence more dangerous/explosive. Volcanic arc - The subducting plate melts and rises its way into the overlying continental crust and sometimes through the surface. This builds pressure in the mantle which eventually erupts as a volcano. (Continental - Oceanic) Island Arc - Over time the subducting plate also pulls down the leading edge of another plate which forms a linear TRENCH. On the subducting plate basalt and oceanic sediments starts melting. This melting creates magma which is much higher in silica, carbon dioxide and water than the magma that originally formed the basalt (MUCH more explosive volcanic eruptions). This molten material begins to rise towards the surface and forms a chain of volcanic islands ‘island arc’ which run parallel to the trench. (Oceanic - Oceanic:) – transform boundaries At conservative margins, plates slide past each other, so that the relative movement is horizontal. Lithosphere is neither created nor subducted, and whilst conservative plate margins do not result in volcanic activity, they are the sites of extensive shallow focus earthquakes, occasionally of considerable magnitude. Module 3: Energy Transformations Role of Energy in the Earth’s Processes
● analyse the role of solar radiation in driving the Earth’s processes, eg photosynthesis and the water cycle
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Oceanic - Oceanic Oceanic-continental Continental-continental
At convergent plate margins, plates are moving towards one another. A trench is created due to the subduction of the denser layer (the older one) and as the layer melts island arcs are created.
At convergent plate margins, plates are moving towards one another. A trench is created as the oceanic crust subducts beneath the surface to melt and raise into a volcanic arc.
At convergent plate margins, plates are moving towards one another. Mountains are formed as the layers are pushed together. There is no subduction and as such not volcanic activity or deep focus earthquakes.
Energy is produced from the sun by nuclear fusion. During nuclear fusion, the high pressure and temperature in the sun's core cause nuclei to separate from their electrons. Hydrogen nuclei fuse to form one helium atom. Energy released from the Sun is in the form of electromagnetic radiation. Photosynthesis The entire biosphere ultimately depends on photosynthesis. The photosynthesis process is driven primarily by the energy from the sun. Without the sun photosynthesis would not occur; leading plants to die as they have no sources of energy. This is a loss of the primary producers and as such the food chain would cease to exist. (loss of diet for herbivores → loss of diet for carnivores). Not only this but the earth would not be able to support respiratory function required for human life as oxygen would become scarce.
Water cycle The water cycle is driven primarily by the energy from the sun. This solar energy drives the cycle by evaporating water from the oceans, lakes, rivers, and even the soil; initiating the start of the water cycle. As such solar radiation drives the water cycle.
● investigate the role of gravity and heat in tectonic plate movements, including:
– comparing the movement of the Earth’s plates to surface movements of other bodies in the solar system
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Carbon dioxide + water → (sunlight, chlorophyll) = glucose + oxygen
Evaporation process by which water changes from a liquid to a gas or vapor. Evaporation is the primary pathway that water moves from the liquid state back into the water cycle as atmospheric water vapor.Particles with enough kinetic energy escape to atmosphere
Precipitation water released from clouds in the form of rain, freezing rain, sleet, snow, or hail. It is the primary connection in the water cycle that provides for the delivery of atmospheric water to the Earth. gravitational potential energy → kinetic energy as droplets fall.
Transpiration evaporation of water through minute pores, or stomata, in the leaves of plants. Evaporation and transpiration are collectively termed ‘evapotranspiration’) Water evaporates from plant leaves (kinetic).
Advection the movement of water — in solid, liquid, or vapor states — through the atmosphere. Without advection, water that evaporated over the oceans could not precipitate over land.
Run off The movement of water across Earth's surfaces. May occur in river channels, creak lines or across flat surfaces. The transformation of gravitational potential energy into kinetic energy.
Description of Surface Evidence of Plate Tectonics Earth Underneath the water that fills the oceans, and
the dirt and plants that cover the continents, the Earth’s surface layer is made of rock. This outer layer formed a hard, rocky crust as lava cooled about 4.5 billion years ago. The tectonic plates are actually floating on the molten asthenosphere which is the lower mantle of the Earth. Earthquakes, volcanoes, mountains, and oceanic trench formation occur along plate boundaries. The plates are in constant motion.
- continental shelves ‘jigsaw fit’ - matching of fossils - age of the seafloor - magnetic reversals and seafloor rocks - ocean floor profile - Subduction zones - Island arcs - Volcanic arcs - Mid ocean ridge - Rift valleys - Hot interior - convection currents
– modelling movement caused by gravity and heat Heat is an essential part of plate movement. Plates move away from each other as a result of the transfer of heat energy from Earth's core to Earth's crust. This is conducted through convection currents. Convection currents are the movement of fluid in a cell (such as the mantle) due to heat and gravity. The process starts with heat energy from the earth core being transferred into minerals, causing them to melt into magma and rise to the Earth's crust. As heat energy is the driving force of convection currents, with the heat removed, the process of convection currents wouldn't be possible as the formation of magma would not occur. As a result, no new oceanic crust can be created and stable tectonic plates. This is also supported through the driving force of ridge push, as it relies on the upwelling of magma to push the older crust out of the way. Again this is not possible, with the heat removed the formation of magma would not occur. So, it is the heat rising from the Earth's Core that is the ultimate source of energy for plate movement, but it is gravity which provides most of the kinetic energy. Gravity generates an active driving component in the direction of motion. Driving forces such as ridge push and slab pull, the most influential driving force which is responsible for more than 90% of ALL plate movement. As a result, both Heat and Gravity are incredibly crucial to the movement of a divergent plate boundary. – describing the contributions of convection and slab pull to plate speed The convection currents are to heat from the core, leading them to decrease in density and rise to the surface. They then drag along the surface as more and more rise together. As they rise and drag along the surface, they start to cool, leading them to increase in density and sink within the mantle. This cycle repeats. The molten magma that rises at a mid-ocean ridge is very hot and heats the rocks around it. As the asthenosphere and lithosphere at the ridge are heated, they expand and become elevated above the surrounding sea floor. This elevation produces a slope down and away from the ridge. Because the rock that forms from the magma is very hot at first, it is less dense and more buoyant than the rocks farther away from the mid-ocean ridge. However, as the newly formed rock ages and cools, it becomes more dense. Gravity then causes this older, denser lithosphere to slide away from the ridge, down the sloping asthenosphere. As the older, denser lithosphere slides away, new molten magma wells up at the mid-ocean ridge, eventually becoming a new lithosphere. The cooling, subsiding rock exerts a force on spreading lithospheric plates that could help drive their movements. This force is called ridge push. At a subduction zone, one plate is denser and heavier than the other plate. The denser, heavier plate begins to subduct beneath the plate that is less dense. The edge of the subducting plate is much colder and heavier than the mantle, so it continues to sink, pulling the rest of the plate along with it. The force that the sinking edge of the plate exerts on the rest of the plate is called slab pull Geological Transformations: Earthquakes, Volcanoes and Mountain Ranges
● explain how the release of elastic potential energy in rock leads to earthquakes Elastic potential energy is a type of stored energy. The elastic rebound theory explains how energy is released during an earthquake. As the plates move under, over and past each other (compression, tension, shearing) the rocks build up elastic potential energy. The rocks bend (deformation) until the strength of the rock is exceeded (elastic limit), whereupon it breaks/fractures or ruptures. When the fault line breaks, energy is released as seismic waves, later becoming kinetic energy as it reaches the surface, causing the ground to shake (earthquake).
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Mars Its surface is rocky, with canyons, volcanoes, dry lake beds and craters all over it. Red dust covers most of its surface. Mars has clouds and wind just like Earth. Sometimes the wind blows the red dust into a dust storm. Tiny dust storms can look like tornados and large ones can be seen from Earth. Mars’ large storms sometimes cover the whole planet.
- Hot interior - Largest volcano known in the solar system - A huge rift valley have been discovered - Seem to have convection currents in a few locations
causing the surface to bulge, stretch and crack
Venus Venus is about 95% the diameter of the Earth. It has no magnetic field, which tells us it’s interior works differently to the Earths at some level. The surface is primarily basalt, like the Earth’s oceanic plates, with no granitic continental plates. The crust is also much younger (several hundred million years) than the estimated age of the planet itself (4 billion years). It has evidence of volcanic activity but little evidence of tectonic interactions and the thick rigid crust.
- Hot interior - Has a few craters on its surface due to meteor
bombardment, implying that the surface has been replaced at some stage from molten material in its interior.
- It has some large but no active volcanoes - faults - folds - mountains - rift valleys.
● describe the role of heat and its interactions with the lithosphere in creating different types of volcanic eruptions and magma compositions, including but not limited to:
– thermal plumes resulting in effusive mafic eruptions Thermal plumes bring abnormally hot magma from deep within the Earth’s mantle to the crust. The mantle and oceanic crust are rich in mafic mineral and lower in felsic content due to density increasing as we travel further below the crust. These mafic, dense minerals found within the mantle form into magma. Thermal plumes, therefore, bring this high mafic magma and low viscosity magma to the surface, resulting in effusive mafic eruptions. – partial melting of subducted oceanic plates resulting in explosive felsic eruptions Partial melting: some but not all of the minerals in a rock melt. Felsic minerals have a lower melting point than mafic minerals. As wet sediment is dragged into the mantle at subduction zones (temperature and pressure increases) water is therefore driven out and causes partial melting of surrounding rock. This lowers the melting point of magma preventing melting of more mafic minerals and producing more felsic magma. Extra silica comes from sediment dragged unto the mantle with subduction plate as well as the overlying plate (as rising magma melts through it). – interactions of magma and overlying ice resulting in ash clouds A typical effusive volcanic eruption occurs first helping to melt some of the glacier. The magma for the second eruption was more felsic and this more viscous. While in a large explosive eruption, the red hot lava interacted with the glacial melt water resulting in a steam explosion which ejected huge clouds of very fine grains ash into the atmosphere. Heat energy transferred from the inside of the Earth has caused melting of ice and is converted into kinetic energy of the rising ash cloud.
● represent these energy transformations in the formation of mountains due to: – thermal expansion The mantle below some regions can become very hot. For example a weak magma plume may rise towards the crust above. This will cause the rock above to expand as well as push them higher. The heat energy in the magma is converted into potential energy of the rising rock, and into causing the expansion of the rock. The most obvious cases are mid-ocean ridges and hotspots which are higher than the ocean floor nearby. This can also occur as land as well. This expansion and lift from below will raise existing land to a higher elevation than expected. – deformation of the lithosphere At convergent boundaries, stress generated at colliding plates give rise to energy transformations. The kinetic energy of the moving plates is converted to elastic potential energy (causing folding) which is converted to heat which deforms and even melts some rocks (metamorphism). If stress continues elastic potential energy can be transferred into kinetic energy (at the ‘elastic limit’ release of seismic waves) when faults rupture Example: The Himalayas Transformations in the Oceans, Biosphere and Cryosphere
● investigate the unique properties of water that make it such an important component of the Earth’s systems, including: - Chemical structure: H20 - POLAR MOLECULE (when there is an electronegativity difference between bonded atoms - The oxygen is slightly negative while the hydrogen is slightly positive.
– boiling point
– ability to act as a solvent
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Significance
- Unusually high for a liquid (100C), due to water’s polarity (polar molecule)
- Takes more energy to break up hydrogen bonds
- Maintains liquid water on Earth from a wide range of temperatures
- High BP vital for living things - If BP of water was lower, tissues of living things
could be damaged
Significance
- Universal solvent → dissolves most things - Water dissolves more substances than almost any
other solvent known. - due to its polar properties.
All the small molecules that are important to life, from salts and sugars to gases, are only useful when dissolved in water (for essential reactions to occur)
- Humans bodies are over 65% of water - Blood flowing in our veins and arteries (over 50%)
– density
– thermal capacity
– surface tension
● outline the roles of energy, water masses and salinity in producing ocean currents Surface currents are driven by wind (top 10% of Ocean water) Gyres are a large system of rotating ocean surface currents
- Clockwise in the Northern Hemisphere - Anticlockwise in the Southern hemisphere
Coriolis effect
- Driven by energy transfer from the wind (and friction between surface waters!) - Earth’s rotation impacts air circulation (drives air in a ‘curved’ path’) - Gyres help to redistribute warmth around the globe!
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Significance
- Density of water depends on temperature - When water freezes it forms ice which is less
dense- this has tremendous implications - The molecules line up and crystallise in the solid
form. - Hydrogen atoms of one water molecule are
attracted towards the oxygen atom of a neighbouring water molecule
- This means they are more spread apart (less dense) than in liquid form.
- Biosphere- floating ice protects marine life and has allowed it to evolve on the ocean floor. (Marine life also depend on glaciers/icebergs on the surface)
- Also means water at the bottom of oceans and lakes does not freeze! (If it did, it could freeze/kill all life living above it)
- Large volumes would be displaced if ice sank every Winter - flooding, rising sea levels
- Floating ice at the poles helps regulate global temperatures by reflecting solar energy back into space.
Significance
Specific heat - number of Joules of energy that is required to increase the temperature of 1 gram of a substance 1C.
- Polar molecules take a lot more energy to increase in heat
- Water has a higher heat capacity than almost any other substance on Earth.
- it can take in or give up a tremendous amount of heat without changing its own temperature.
- As living things are mostly made from water, this high thermal capacity prevents them from heating too much from the Sun
- Allows water bodies to remain stable - The environment inly causes small, controllable
temperature changes
Surface tension = property allowing liquid to resist external force
- caused by the polarity of water (surface tension results as water molecules are attracted to each other, forms stronger bonds)
- This attraction is referred to as cohesion - It results in a ‘film’ on the surface which is more
difficult to break
Deep ocean currents are driven by changes in densities (remaining 90%) Thermohaline circulation:
- As water approaches the poles, it cools - Also has higher concentration of salt (because when ice crystals form, salt is not integrated into the ‘lattice’) - This cold, salty water is more DENSE and therefore sinks - When it reaches the bottom of the ocean floor, it moves towards the equator (warming up and rising) - Meanwhile, warm salty water from the tropics flows towards the poles as part of a convection current.
These two circulations are interconnected to form a global ocean conveyor belt.
- Transports warm water from the equator to polar regions and cold water to equatorial regions (helping to even out temperatures around Earth
- As water travels from the depths of the ocean to the surface ‘upwellings’ it carries NUTRIENTS which are essential to microorganisms that form the basis of ocean food chains
● explain the role of heat transfer by ocean currents and atmospheric movement in causing phenomena
El Nino Southern Oscillation is an irregular, repeating variation in wind speeds and sea temperatures over the equatorial Pacific Ocean Normal conditions: ‘Walker Circulation’
- Under normal conditions (50% of the time) , currents and strong winds (‘trade winds’) bring warm air to Indonesia and North Queensland.
- This is driven by high pressure in East and low pressure in the West - As this warm water is moved away, colder water rises to take its
place ‘upwelling’ - The warm water evaporates, producing warm, wet air. The warm
air rises, where it cools and the moisture condenses as rain. - Cooler, drier air is then descending on the other side of the ocean
La Nina
- The trade winds and currents are much stronger and the water that reaches Australia is even warmer. (Shift is more West than usual!)
- Pressure difference between East (high pressure) and West (low pressure) is large
- South America is much drier than usual - Australia experiences heavy rain and flooding
El Nino
- During El Niño events, the trade winds are much weaker and the warm water flows away from Australia.
- When this occurs, there is very little pressure difference between the east and west Pacific.
- Australia experiences drought and dry, hotter temperatures - South America receives greater rainfall, flooding, mudslides, crop
loss
● extract information from secondary sources to document and investigate changes in the cryosphere The cryosphere is the frozen part of the hydrosphere. Includes all glaciers, ice cap, ice sheets, sea ice, snow and permafrost (frozen soil) Albedo Effect “Albedo” - measure of the amount of sun that is being reflected back into space. The cryosphere has a higher albedo (white) as rge reflects more sunlight, causing a colder climate. Rainforest, dark ocean water and soil have a lower albedo and therefore have warmer climate Global warming Impact Overall trend in increasing temperatures, ultimately resulting in a shrinking of ice - snow coverage. Reduction in the cryosphere can cause a spiral effect creating situations that cause conditions that result in more ice melting. Impacts on agriculture - glacial retreat Many agricultural communities and ecosystems in areas near glacial regions, rely on glacial melt for fresh water. Predictions show that glaciers will completely melt and communities will need a new water source.
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Permafrost Permafrost is frozen soil (year round) for at least 2 years. Ice acts as cement to bind rocks, sediment and soil together. Has LARGE quantities of methane gas and carbon dioxide trapped within it (estamied TWICE as much carbon currently in our atmosphere) Sea Ice The loss of sea ice from the arc ocean could have profound effects on the animals which live there and on the earth;s albedo and possibly on the thermohaline circulation (cooling the water) For example, polar bears due to the decrease in sea ice make it harder to hunt as they lose the element of surprise. Ice sheets Ice sheet is a mass of glacial land ice existing near greenland and Antarctica that are responsible for 99% of fresh water. Intergovernmental panels of climate change predict a rise in sea level by 25m. This will cause destructive storm surges, contamination of fresh drinking water, loss of habitat, destruction of coral ecosystems and more intense cyclones. Not only this but low lying agricultural communities could be displaced. Module 4: Human Impacts Water Management
● represent the distribution of the Earth’s water, including the amount available to plants and animals Water Uses
- Every living thing uses water - Humans 60% of body mass
○ In cells ○ Blood plasma ○ Essential for good health / chemical reactions
- Animals and plants - Importance for agriculture, industry and recreation
Distribution of Earth's Water Only 3% of global total (most of this existing as ice and snow in the cryosphere) This leaves very little fresh water available for humans and terrestrial organisms As a precious resource, the fresh water available to life and humans needs to be shared amongst the biosphere. Industry and agriculture take up more than human’s fair share of freshwater and poor management often leads to water crises in some communities.
● investigate the treatment and potential reuse of different types of water, including but not limited to:
– industrial wastewater Industrial wastewater is water that has been used as part of making a commercial product. Water becomes contaminated after use, depending on the industry, and must be treated accordingly before it returns to the local waterways. Power Plants Power stations, such as coal or nuclear power, work by heating water and spinning a turbine. The heated water cannot be returned to the waterways straight away, as it can heat local aquatic ecosystems, causing thermal discharge. Organisms can be killed by abrupt changes in temperature. Warm water holds less dissolved gases, such as oxygen, and more soluble solids, such as salts, than cold water. This can alter the chemistry of these environments, affecting the organisms that live there (and negatively impacting entire food webs). Heated water from power stations has to be cooled to the same temperatures as local waterways before it is released. Manufacturers Insoluble organic compounds, such as plastics and oils, can be removed from used water by physical means, such as filtration and skimming.
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Mines Water discharge from mines often contains waste rock (tailings), which can lead to decreased pH (increased acidity) and heavy metal contaminations. This is some of the worst and most environmentally destructive type of artificial water contamination. Example: Coal Mine Treatment
– sewage
– stormwater Stormwater is water that falls on sealed surfaces and anything that is carried with them E.g. rubbish, animal waste, oil, household chemicals and leaves Gross pollutant traps (GPT) GPTs act like a filter, retaining litter but allowing water to flow through. Over time, debris builds up in GPTs. They must be cleaned to ensure that water can flow through and that the collected rubbish does not leach pollution into the water. ( it does not collect nutrients/pesticides or heavy metals) Artificial wetland Remove excess sediment as water flow slows down and can settle by gravity. Nutrients are taken up by vegetation and bacteria break down organic materials. Wetlands provide a habitat and attractive landscape feature and effectively clean storm water before it enters creeks and river systems. Trash rack A trash rack is a wooden or metal structure that screens/ filters out water-borne debris (such as logs, boats, animals, masses of cut waterweed, etc.) from entering the intake of a water mill, pumping station or water conveyance.
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● Describe ways in which human activity can influence the availability and quality of water both directly (eg over-extraction) or indirectly (eg algal blooms)
Plastics
- Plastic is lightweight, durable, cheap, easy to make and can be moulded into many different shapes. Because it is so durable, plastic takes between 400-1000 years to break down
- Yet only 9% recycled, 12% burned and 79% still around… most of it in our oceans - Lots of animals starve with stomachs full of indigestible plastic. As their stomach believes they are full of plastic they
don't think they are hungry and stave. Microplastics - plastic less than 5 mm
- Plastic is not biodegradable but it IS photodegradable → sunlight breaks it down into tiny pieces (microplastics). - Commonly mistaken as plankton, microplastics are devoured by everything from krill to whales
Danger of Plastic
- Lots of toxic chemicals are added to plastics → if these are eaten by fish it can have a damaging impact on marine animals and the organisms that eat them (including us!)
- BPA (hormonal implications) - DEHP (carcinogenic) - In addition, plastics absorb and concentrate other pollutants in the water (i.e. mercury, DDT) - Plastic pellets have been found to concentrate toxins up to a million times more than the surrounding sea water
Biomagnification Biomagnification refers to the increased concentration of a toxic chemical the higher an animal is on the food chain
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Eutrophication (algal bloom)
Over extraction
- Over Extraction of groundwater will eventually cause the water table to drip below bore levels so that users can no longer pump out water, directly affecting the water users. The indirect excessive use is the drying up of wetlands, rivers and lakes
- Ground water is needed for agriculture, irrigation and natural environments also depend on groundwater to maintain ecosystems
- For a long time, use of groundwater had no limits and wasn’t monitored and was being used at an unsustainable rate Seawater intrusion
- Saltwater intrusion occurs when over extraction of groundwater causes salt water to move into parts of an aquifer that is usually freshwater (more typical near oceans)
- Drop in water pressure results acts like a ‘straw’ to draw salt water into aquifer - Water being withdrawn from the aquifer becomes increasingly saline and unsuitable for use
Pollution
- Most pollutants move through aquifers at even slower rates than water, meaning contamination can not be quickly flushed away.
- Pollution can come from ○ Industry (sewage, hazardous wastes, garbage and landfill- disease causing bacteria ) ○ Agriculture (fertilisers, pesticides) ○ Mining (heavy metal poisoning, tailings water, acidic water
- Pollution of large aquifers is currently too expensive and/or difficult to reverse. This pollution has serious impacts on human and ecosystem health
Salinity and Erosion
● explain causes of salinisation, including but not limited to: - Salinity refers to the presence of salts. - Primary salinity refers to salinity which is naturally occurring in water and/or soils
○ Connate salts: Fossil salt deposited in ancient oceans when Australia was submerged. ○ Aeolian salts: Rain carried inland from sea spray or salt bearing sedimentary deposits ○ Salt lakes: Accumulates salt from aeolian sources.
- Secondary salinity occurs when human actions cause alienation of water and/or soil Dryland salinity
- In semi-arid regions of the country, the water table underground is kept in balance by native trees and vegetation. - The deep-rooted perennial (year round) trees absorb most water that enters soil and returns to the atmosphere via
evapotranspiration (from leaves and soil). - Therefore the water added to soils by rainfall, called recharge, is roughly the same as the water used by the
deep-rooted trees. This is called the water table discharge. - This keeps a stable balance between new water, such as through rainfall, and removal of water; the sub-terrestrial
(water table) water levels are kept well below the surface. Land clearing
- Land clearing to make room for shallow rooted crops which only grew part of the year - Absorbed only a fraction of rainfall compared to that of native deep-rooted vegetation. - Reducing transpiration and increasing runoff and infiltration - This raises the volume of the water table which brings dissolved connate salts with it.
Impact - In low-lying areas the salt may reach the surface. - DECREASED agricultural productivity- land is now infertile and crops will no longer grow (Evaporation leaves a “salt
scald” where nothing can grow.) - DECREASED biodiversity--> Saline groundwater can also mix with surface water. An increase in salinity can potentially
impact freshwater aquatic species (and terrestrial animals which depend on this water body as a drinking supply)
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Irrigation
- Irrigation (artificial addition of water to land or soil) - Inefficient use of this irrigation(e.g. excessive) contributes to salinity - Because irrigated land is typically also land cleared (crops for agriculture), this leads to an even greater volume of water
infiltration causing a rise in the water table (containing dissolved connate salts). Impact
- Increased salinity in soils can cause increases in erosion due to low vegetation cover, increased salinity in rivers and streams, and threaten local ecosystems and wildlife populations of hundreds of native species.
● investigate the rehabilitation of salinity-affected area(s) by preparing a case study
Liverpool plains, Gunnadah Cause
- Widespread clearing of native perennial vegetation - Planting of crops (shallow rooted) which were harvested (leaving soil exposed for long periods, transpiration rates were
consequently very low and water table continued to rise) - Water table rose to approx. 5cm below the surface (bringing saline waters with it).
Issue
- This produced increased flooding and waterlogging, reducing the area that could be farmed. - Many species of natives and crops died as a result of increased salinity levels reaching root levels. - Salinity levels in fresh water sources were also increasing. This was affecting other farms, the river ecosystem and the
native animals which rely on the river for drinking water. - Dryland salinity was a major problem
Fix
- Paddocks were replanted to include small trees. Only 5-10% of cropping areas were reduced but productivity went up. - Pines and Eucalypts were planted on hills and sloped where water recharged the groundwater. The trees took on the
excess water. - Crops were rotated with saltbush (salt tolerant pasture species) and alfalfa ‘lucerne’ (deep-rooted pasture species). This
meant that land wasn't always used for normal crops but was still being utilised between seasons. The alfalfa ‘lucerne’ could be used for hay production and also added valuable nitrogen to the soil.
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