Earth and Environmental Science Prelim Course Notes.docx

Module 1 Earth's Resources ========================== 1.1 Structure of the Earth, the Early Geosphere, Atmosphere and Hydrosphere --------------------------------------------------------------------------- ### **The Protoplanetary Disc** 1. An area of dust and gas contracts due to shockwaves fro...

Module 1 Earth's Resources ========================== 1.1 Structure of the Earth, the Early Geosphere, Atmosphere and Hydrosphere --------------------------------------------------------------------------- ### **The Protoplanetary Disc** 1. An area of dust and gas contracts due to shockwaves from a nearby **supernova**. 2. Within this **protoplanetary disc**, particles clump together + cloud rotates at a faster rate, causing most material to be located in a central sphere. 3. Due to huge internal pressures, this sphere became hot and formed a **protostar.** 4. Debris within disc surrounding the protostar gathered into **protoplanets** through **accretion** (gathering of small bodies due to gravity) 5. Gravitational squeezing caused temps and pressures to increase within the protostar, until a critical rate was reached in which **nuclear fusion reactions** could occur. Hydrogen atoms fused to make helium atoms. 6. This process released lots of energy, causing the star to ignite and become a **true star**. ! Why are the inner planets rocky? Because ignition blew away the surrounding gases ! The Formation of the Earth 1. The infant Solar System contained hundreds of small protoplanets with overlapping orbits, constantly being bombarded with meteorites and sweeping into each other, increasing each planet's size and mass. 2. Rocky planets such as Earth heated rocks to melting point, releasing gases from within, forming the atmosphere. 3. Heavier metallic elements sank deep into liquid Earth and lighter elements floated to the surfaces (**differential heating**) 4. Eventually planets settled into stable orbits, cleared the space around them of debris, experienced decreasing meteorite impacts and began to cool. ### **The Formation of the Moon** 1. 4.5 bya, a Mars sized body impacted Earth, propelling a shower of debris into space (from both Earth and Mars sized body) 2. The impact sped up Earth's rotation and the moon aggregated from the debris 3. Earth reformed as a largely molten body ### **Formation of the Atmosphere** The 4 layers sorted based on temperature, air pressure, altitude [Earth's original atmosphere vs. current atmosphere] - ---------------------------------------------------- ----------------------------------------------------------------- ---------------------------------------------------------------------------------------------------- Original Current Comparisons Nitrogen Nitrogen Original atmospheric nitrogen remains as it is unreactive. Carbon monoxide/dioxide Carbon dioxide Early atmosphere contained 100-1000x more. (combined with Cl and Mg in seawater to form limestone) Hydrogen - too light, lost into space Oxygen - waste produced by plants during photosynthesis Water vapour - vented from molten rock Water vapour - additional water from meteorites More water in the current atmosphere. Methane - reacted w/ oxygen to produce CO2 and H2O Argon - produced by radioactive decay of elements within mantle ---------------------------------------------------- ----------------------------------------------------------------- ---------------------------------------------------------------------------------------------------- ### **Formation of the Hydrosphere** 1. Icy bodies from space - Far away chondrites that contained ice formed beyond the protoplanetary frost line, away from solar winds. These were probably carbonaceous (contained organic matter) and travelled to Earth. 2. Volcanic outgassing - (More likely theory as volcanoes produce alotta water) Molten surface of the Earth released abundant water vapour into the atmosphere which condensed and formed thick rainclouds, which fell onto Earth. ### **Structure of the Earth** Crust - Continental vs Oceanic ---------------- ------------------- ------------------------- **Properties** **Continental** **Oceanic** Thickness 25-70km 5-10km Density 2.7 g/cm\^3 2.9 g/cm\^3 Rock type All 3 e.g granite Only igneous e.g basalt ---------------- ------------------- ------------------------- Mantle - Olivine is found here - Pyroxene too - **Upper vs Lower** --------------------------------- ------------------------------ **Upper** **Lower** Rigid, mantle plumes occur here Plastic, convection currents 1000 degrees Celsius 3700 degrees Celsius --------------------------------- ------------------------------ Core - Haematite is found here - The movement of the iron in the core affects and is the cause of the magnetic field around earth. - **Outer vs Inner** --------------------------------------------------------------- ----------------------- **Outer** **Inner** Liquid, not under much pressure Solid, high pressure Nickel and iron, generates Earth's magnetic field as it moves Nickel and iron alloy --------------------------------------------------------------- ----------------------- ### **Investigating Evidence for the Structure of Earth** - As Earth grew, its **gravity** also grew, attracting a hail of **meteorites**. - This period of bombardment melted the rocks and allowed the elements to **differentiate** according to density. - Meteorite strikes reduced as Earth swept its path free of debris, allowing Earth's surface to cool over the hot interior. ! Earth's interior remains hot till today as radioactive decay of some elements occurs, releasing heat energy ! Seismic waves - Love (L) Waves -\> Surface waves created when the epicentre is reached. Slowest but most destructive waves and shake the Earth side to side. - Primary (P) Waves -\> First waves to show up on seismographs. Fastest waves and travel through solids and liquids. Compression waves. - Secondary (S) Waves -\> Produced at focus. Transverse waves and travel through solids only, and show up after P waves. ! S-P Interval (difference of arrival time between s and p waves) allows seismologists to determine location of focal point ! Meteorites - Meteorites are the leftover bits that didn't accrete during the formation of the solar system. - This means the rock composition of these meteorites would be similar to that of Earth's, telling us Earth is made largely of silicate minerals with a significant chunk of iron/iron compounds. ### **Evidence of the Earth's Age** Formation and Age of Zircon Crystals - Zircon crystals come from the crust of the early Earth. - Uranium-lead dating is used to date these crystals - They have a ''locked'' crystalline structure which resists change, therefore, providing a reliable age of the Earth. - Radiometric Techniques - Atoms in igneous rock start to decay and form radioisotopes the moment the rock crystallises, making dating of these rocks an accurate process. Meteorite Evidence - 1.2 Rocks, minerals and the rock cycle -------------------------------------- ### **What are minerals** To be a "mineral" a substance must; - Be naturally occurring - Be inorganic (not made by an organism - Be Solid (at standard temperature and pressure) - Have a definite mineral composition (all occurrences must have a specific composition only varying within a specific limited range) - Have an ordered internal structure (atoms are arranged in a systematic and repeating pattern) ### **Physical and chemical properties** Each mineral type has a specific chemical composition and specific chemical properties. Silicate minerals (SiO4 group) - Are the most common on Earth - Most silicates form as molten rock cools and crystallises - Conditions and environment in which cooling occurs determines what type of silicate forms Silicate minerals fall into two categories; - Felsic minerals - Examples Granite and Rhyolite - Mafic minerals - Examples Gabbro and Basalt - Common at divergent zones -  ### ### **Classification** Field tests for classification of minerals include; H[ardness] A mineral's resistance to being scratched - Determined by rubbing against other minerals that we know the hardness of - The softer of two substances gets scratched - If two substances are equal hardness they both get scratched - Moh's hardness scale - know how to read it L[ustre] How shiny a mineral's surface is - Subjective terms- metallic and non-metallic - Non-metallic lustres for common minerals include generally; metallic, glassy and earthy Streak - The observed colour of a mineral can be misleading due to impurities - When powdered- a minerals colour is called its streak - Found by scraping a mineral on an unglazed white tiel Density/specific gravity Describes a mineral's density relative to water; -. - Density of water is 1g/cm^3^ and its specific gravity is 1 - Most metallic minerals have a higher density (\>3.5) - Mass Cleavage and Fracture - How a mineral naturally breaks/splits according to lines of weakness based on crystal structure - cleavage - Break in uneven but identifiable way - fracture ### **Formation of Rocks and Minerals** #### Rocks Igneous - Chemical composition - Light coloured -\> silicate minerals e.g feldspar - Dark coloured -\> ferromagnesian minerals e.g olivine - Texture - Extrusive igneous - formed by lava and have small crystals due to the cooling effects of earth's atmosphere - Intrusive igneous - formed by magma and have large crystals as they have cooled slowly over a long period of time. Weathering and erosion can reveal these coarse grained rocks to the surface. Sedimentary Formed in layers called strata - law of superposition (layers get younger as move up a rock sample, unless it has been overturned) - Clastic - Formed by weathered and eroded sediments that have been deposited and cemented together. - Classification by size of particles (big -\> small) : Conglomerate, Sandstone, Shale/Mudstone - Chemical - Chemical precipitation - Biological activity - 1\. Animals shells (made of calcium carbonate) sink to ocean floor to form rocks such as ORGANIC (coz biotic) limestone/chalk - 2\. Vegetation in swampy areas does not fully decompose due to lack of oxygen and forms coal. Metamorphic - **Contact metamorphic** - altered by heat from close contact with molten rock. Form a narrow band around igneous rocks - **Regional metamorphic** - altered by high pressures when tectonic plates collide causing folds in rocks. Occur over a larger area than contact. +-----------------------------------+-----------------------------------+ | **Foliated** | **Non Foliated** | +-----------------------------------+-----------------------------------+ | Smooth appearance | Granular/ grainy appearance | | | | | Caused by regional metamorphism. | Caused by same | | | | | Flaky minerals aligned in | E.g marble and quartzite | | parallel structures called | | | foliations. | | | | | | E.g slate and gneiss | | +-----------------------------------+-----------------------------------+ Different rocks can be formed based on pressure and intensity. Examples: - Shale -\> Slate -\> Gneiss (multiple stages) - Limestone -\> Marble (only one possible change) #### Rock Cycle  #### Formation of Soil 1. Soil Structure +-----------------------------------+-----------------------------------+ | Layer | Descriptions | +-----------------------------------+-----------------------------------+ | A horizon | Darkest because contain alotta | | | humus (organic matter) | | | | | | Insoluble minerals like clays | | | | | | Zone of leaching | +-----------------------------------+-----------------------------------+ | B horizon | Brightest colour | | | | | | Little organic matter like roots | | | | | | Soluble minerals and iron oxides | +-----------------------------------+-----------------------------------+ | C horizon | Pieces of bedrock mixed with clay | +-----------------------------------+-----------------------------------+ | Bedrock | Underlying unaltered rock of | | | environment | +-----------------------------------+-----------------------------------+ 2. Factors Affecting Soil Formation a. Bedrock (Geologic) - Rocks resistant to change breakdown produce thin soils - Little variety of minerals cause infertile soil b. Climate (Atmospheric) - Cold and dry -\> thin and little organic matter. Only physical breakdown of rocks - Hot and wet (tropical) -\> Chemical breakdown more active and encourages plant growth. Results in thick solid rich in organic matter. c. Topography (Geologic) - Soil on steep slopes -\> thin and move downhill with erosion d. Water movement (Hydrologic) - Lateral movement - Vertical movement which is just leaching e. Plants and animals (biotic) - Decomposers break down organic matter - Roots and organisms aerate soils 3. Soil and Life a. Loam soils are ideal for growing the majority of plants. 4. Soil Texture Know how to use triangle ----------------- ---------- ------------------- -------------- ------------------------ Soil texture by Aeration Nutrient capacity Infiltration Water holding capacity Clay Poor Good Poor Good Silt Medium Medium Medium Medium Sand Good Poor Good Poor ----------------- ---------- ------------------- -------------- ------------------------ 5. Soil Chemistry f. pH is important as certain minerals are only obtainable by plants at specific pH levels g. NPK (Nitrogen, phosphorus, potassium) ratio is important for fertilising plants 1.3 Geological Time Scale ------------------------- ### **Relative Dating** 1. Stratigraphy a. **Law of Superposition** - The age of the rock increases as you move further down the layers. b. **Law of Crosscutting** - When rocks fracture and a fault is formed, it is younger than the rock it cuts through. c. **Law of Inclusions** - Fragments of a rock must be older than their host rock. 2. Correlation - Index fossils in a rock allow geologists to map the dates of rocks on a wider scale. - Criteria: short lived and widespread ### **Absolute Dating** Igneous rocks contain radioactive minerals which decay overtime. Specialists can read this decay using technology to find the absolute age of a rock sample. ### **Geologic Time Scale** Know how to read the geologic timescale, given in the formula sheet. 1.4 Geological Resources ------------------------ **Natural resources** are materials or substances occurring in nature which can be exploited for economic gain. +-----------------------------------+-----------------------------------+ | Renewable (SUSTAINABLE) Resources | Nonrenewable Resources | +-----------------------------------+-----------------------------------+ | Can be replaced over a relatively | Nonliving resources which we need | | short period of time and | but cannot be replaced within any | | therefore can be exploited | reasonable time. | | forever. | | +-----------------------------------+-----------------------------------+ | - Wind | - Coal | | | | | - Hydropower | - Natural gas | | | | | - Biomass | - Petroleum | | | | | - Geothermal | - Propane | | | | | - Fishing/hunting/farming | - Uranium | +-----------------------------------+-----------------------------------+ ### **Economic Importance** - **High value resources** are profitable to mine in remote locations and/or low concentrations. For example, all metallic resources and coal, petroleum. - **Low value resources** are profitable to mine in remote locations in HIGH concentrations, and are usually not exported. For example water, cement, sand and clay. ### **Location of Australia's Non Renewables** 1. **Fossil Fuels - byproducts of the decomposition of living organisms such as plants.** a. [Coal] - Produced from once living plant material. ---------------------- ------------------------------------ **Rank** **Description** Peat Fibrous decomposed materials Brown coal / lignite Contains some woody materials Sub-bituminous coal Hard, blotchy, dark, slight lustre Bituminous coal Black, lustrous & strongly banded Anthracite Metallic lustre and no bands ---------------------- ------------------------------------ b. [Petroleum] (crude oil and natural gas) - Slippery compound composed of organic compounds extracted from the ground. - Plants and animal remains trapped in sediments get transformed by heat and pressure over MOY. - Crude oil - classified based on density and ability to move between grain and sediments - Tar sands - does not flow into wells drilled into sand - Heavy oils - move slowly so can be extracted from wells if given time and help - Medium and light oils - moves freely through sediments and recoverable. c. [Gas] - Coal seam gas - form of natural gas extracted from coal beds with high methane levels - Natural gas - Occurs with crude oils - Liquefied petroleum gas (LPG) - Mixture of petroleum gases, stored as a liquid under pressure. 2. **Minerals and Ores of Economic Significance** - A mineral deposit is a mass of concentrated occuring mineral. If it has high economic value to mine, it is an ore. - Natural processes leading to concentration of minerals - Hydrothermal - Magmatic - Sedimentary - Placer - Residual ### **Discovering New Resources** 1. **Remote Sensing Techniques** a. Satellite imaging - infrared and visible b. Aerial photography 2. **Direct Sampling** c. Magnetic techniques - (magnetometers) d. Gravitational measurements - (gravimeter) e. Seismic methods - by measuring reflections, or refractions or scattering of shock waves f. Drilling Aboriginal Quarrying and Mining Methods ### **Extracting the Resources** Surface mining - - Open pit is the cheapest form of mining and covers large areas of land. Used for coal/tar sands/metals - Dredging and hydraulic is useful near bodies of water along coastlines and streams. Used predominantly for gold and tin. Underground mining - - Audit if extracting ores from a deeper open cut mine - Declines are spiral shafts for shallow deposits to 200m (nickel) - Vertical shaft - When ores can be more than 1 km deep like on mountains Solution mining - - Natural solutions - used to extract salts from salt lakes/ponds - Artificial solutions - added solutions to dissolve minerals, used to extract gold left behind in mine tailings. Offshore - petroleum and natural gas Onshore- crude oil and natural gas Module 2 ======== 2.1 Evidence of the Theory of Plate Tectonics --------------------------------------------- - The modern theory of plate tectonics states that the Earth's outer layer (lithosphere) is broken up into several large plates which are constantly moving. ### **Analysing Evidences** 1. Jigsaw fit of the continental shelves and matching up of identical fossils - Various features such as mountain ranges, sedimentary deposits and specific fossils, when placed together, align. - wide distribution of seed fern fossils Glossopteris - The Appalachian Mountains of eastern US match mountain ranges of similar age in Scotland/Scandinavia 2. Age of seafloor rocks and profile of the ocean floor - - Samples of rock collected by drilling into the sea floor from ships such as the Glomar Challenger were dated using radioisotopes. It showed that rocks get older as you move away from MORs. This means new rock is constantly being formed at MORs explaining why the temperature is much higher in those areasprovides. - Satellite cameras give a rough estimate of ocean depth - Sonar technology bathymetric data which is much more accurate in measuring depth. 3. Magnetic reversals in seafloor rocks - For unknown reasons, the polarity of Earth's magnetic fields reverses every few million years. Some oceanic rock forming minerals (basalt rocks) have magnetic properties- they align themselves towards the magnetic north pole. - These [may] be caused by changes in the convection currents of molten iron in the earth's upper mantle and outer core. ### **Geographic VS Magnetic North Pole** The fixed point that we call the geographic North pole at the top of the earth. The magnetic North pole is a point on the Earth's surface where the magnetic field points down, which moves over time due to magnetic changes in the Earth's core. - The flow of an electric current generates a magnetic field Paleomagnetism: The study of the record of the Earth's magnetic field in rocks ### **Evaluating Theories, Models and Research** What is a theory? - A scientific law is a description of an observed phenomenon - A theory is a proposed explanation of a phenomenon, for which there is a large body of evidence - A law predicts what happens while a theory aims to explain why - Cooling Earth hypothesis - Prior to 20th century they thought continents were fixed in position, and the surface shape was the result after cooling of molten rock from the early planet, then shrinking from thermal contraction causing the crust to become fractured and distorted - Alfred Wegner - Continental drift - Fascinated by jigsaw fit of continents - Collected evidence but couldn\'t explain which forces were capable of causing continental movement - Suggested possibilities- Earth's centrifugal force and tidal pull from the moon- but mathematicians deemed this impossible - Harry Hess - Sea floor spreading - Observed guyots- flat topped underwater volcanoes - Seafloor profiles he collected meant the ocean crust was moving away from the mid ocean ridges - Arthur Holmes - Mantle convection currents - Used radiometric dating techniques - Developed idea that convection currents in the mantle could move continents - Fredrick Vine and Drummond Matthews - Explained magnetic banding and changing polarity of magnetic field - As magma reaches the surface at mid ocean ridges it solidified - Solidified magnetic rocks facing one way would record how the magnetic field itself reversed since then - The Glomar challenger discovered the oceanic crust is no more than 200 million years old (the earth is 4.5 billion years old)  --------------------- 2.2 Plate Boundaries -------------------- ### **Divergent** - Separating plates - New crust generated - Volcanically active -\> basaltic lava flows through fissures and is low in silica therefore low viscosity. - Typically elevated at surround terrain as they are pushed upwards by convection currents - Shallow focus earthquakes - Little to no metamorphism ### **Convergent** I. and II. Oceanic - continental and oceanic - oceanic - Initial point of subduction indicated by deep ocean trench - Intensely folded mountain ranges for oceanic continental, island arc chains for oceanic oceanic - Andesitic volcanism and granite magma intrusions - Metamorphic rocks present - Shallow to deep focus earthquakes - Growth of continental crust III\. Continental - continental - Forms high mountain peaks- e.g. Himalayan Mountain Ranges - Shallow earthquakes - Metamorphic rocks formed due to the slow collision of crust ### **Transform** 2.3 Plate Boundaries and Tectonic Structures -------------------------------------------- ### **Divergent Boundary** - Convection currents rise and move in opposite directions. - This pushes the lithosphere up and horizontally from beneath it, - Flow causes material above to be dragged along in the flow\'s direction. - Plate is stretched thin, breaks and pulls apart. #### Mid-ocean Ridge - Continuous range of underwater volcanic mountains. - As plates separate, molten basalt flows through the fissures, resulting in seafloor spreading. - Example: South-East Indian Ridge #### Rift-Valleys - Build up of heat in the asthenosphere beneath continental crust results in expansion of the asthenosphere. - This pushes up continental crust which then cracks as plates move apart. - A block of crust between the 2 sides drops to form a valley. - Example: East African Rift Valley #### Normal and Transform Faults Normal: Block above fault moves downwards ### **Convergent Boundary** - Two plates move towards each other due to convection currents created by heat in the asthenosphere. - When they collide, it usually forms a subduction zone, where one plate moves beneath the other. #### Mountain Ranges #### Trench #### Reverse faults and folds Module 3 Energy Transformations =============================== 3.1 Role of Energy in the Earth's Processes ------------------------------------------- - Know how to describe movement of convection currents in the asthenosphere ### **Role of Solar Radiation in the Earth's Processes** - Nuclear fusion - Huge pressures and temperatures in the centre of the sun cause Hydrogen atoms to move so fast they collide into each other and fuse to form helium nuclei. - The energy is released (EM Radiation) causes the sun's surface to be 5500 degrees Celsius - Earth is located in the habitable zone, where the right amount of energy reaches us. ### **Convection currents** - Convection currents occur in all unevenly heated fluids - Convection currents are driven by the effect gravity has on different densities within a fluid - The magma slowly rises above the hottest parts of the mantle and collides with the lithosphere causing it to spread sideways - The mantle is the main force that is causing continental drift, along with ridge push and slab pull - Ridge push can slab pull are both affected by gravity, just like convection currents - Apply this knowledge to the practical about the corks in a beaker ### **Photosynthesis** - The process in which plants manufacture their food - Chemical equation: 6CO2+6H20---\>C6H1206+602 - Chloroplasts are a pigmented organelle - Chloroplasts trap energy from the sun and store it as chemical potential energy - With this, 2 types of reactions occur: - Light dependent: uses energy captured from the sun to split water molecules into oxygen and hydrogen atoms - Light independent use the carbon dioxide from the atmosphere, oxygen atoms and hydrogen gas to produce glucose (stored energy) Light independent reaction - Also known as the calvin cycle - Occurs in stroma - Also known as the dark reaction but does not happen in the dark and rather uses light Light dependent reaction - Occurs in thylakoids - Water is split during this reaction - Produces chemical energy (ATP, NADPH) - A collective stack of thylakoids is called a granum (looks like green pancakes) Respiration - Glucose+oxygen--carbon dioxide and water ### **Water Cycle** - Environmental cycle- any process that has a substance being cycled through different parts of the environment - Water cycle- the process of water being cycled through the various parts of the earth - Right before the process of precipitation, the water particles stay suspended in the clouds, due to convection currents in the atmosphere ### **The role of gravity and heat in tectonic plate movements** - Low density materials float towards the outside of the earth - High density materials sink towards the core of the earth ### **Evidence regarding mars and it volcanic activity** - There is volcanic activity in mars as the largest volcano in the solar system resides in mars, due to this convection currents seem to be in a few locations around the planet, which in turn causes the surface to bulge, stretch and crack. Further implying the surface has been replaced with molten material. Mars has some large but not active volcanoes0 ### **Contribution of convection and slab pull** - Due to particles being close together but not fixed in position, they constantly move around - While heating up, the particles move faster, and collide faster and harder - Following this collision, they push each other away causing an increase in volume - If heated long enough the liquid particles will push each other away to the point where they become a gas - density=mass/volume, where the volume increase the mass stays the same but the density gets lower - A convection cell is formed because of hot mantle rock near the core rising due to lowered density 3.2 Geological Transformations: Earthquakes, Volcanoes and Mountain Ranges -------------------------------------------------------------------------- ### **Elastic Potential Energy and Earthquakes** +-----------------------------------+-----------------------------------+ | **Causes of Earthquake** | **Effect of Earthquakes** | +-----------------------------------+-----------------------------------+ | EPE is stored in an object when | Primary waves: Fastest, first to | | there is a temporary strain on | be detected, compression waves, | | it. | pass through solid and liquid | +-----------------------------------+-----------------------------------+ | The release of seismic waves | Secondary waves: Slower than P, | | occurs when tension is released | transverse shear waves (move like | | due to shear forces and | rope fixed at one end and | | compressions. | shaken), pass through solids. | +-----------------------------------+-----------------------------------+ | The first point of breakage | Surface waves are slowest and | | underground is called the Focus. | move along the surface, causing | | | destruction. | | | | | | - Rayleigh | | | | | | - Love | +-----------------------------------+-----------------------------------+ | Waves spread out in all | Rayleigh -\> vertical motion of | | directions, but the point on the | particles | | surface directly above (the | | | epicentre) experiences the | Love -\> horizontal shaking | | strongest shaking. | (noticed by ppl) | +-----------------------------------+-----------------------------------+ ### **Role of Heat and it's Interaction with the Lithosphere** - Heat and gas trapped within the Earth's crust can only escape through **fissures** - Magma within the mantle is under great pressure. Heat energy transferred from within the mantle causes gases to expand, increasing the **pressure**, a form of **potential energy** ready to be released. - If any channels are open to the surface, the pressure forces magma up, usually through **magma chambers** rather than the mantle directly. - Magma chamber -\> act as a reservoir for magma and dissolved gases - **Viscosity** is determined by temperature and silica content #### Volcanic Hotspots - Area in the mantle from which heat rises as a mantle plume. - High levels of heat at the base of the lithosphere facilitate melting of rock. - Melted material makes its way through fissures in the crust, erupting to form volcanoes. - Tectonic plates move over the stationery hotspot, and new volcanoes begin to form. (Hawaiian Islands) #### Eruptions +-----------------------------------+-----------------------------------+ | **Effusive Mafic** | **Explosive Felsic** | +-----------------------------------+-----------------------------------+ | Low silica content and high | Rich in elements forming feldspar | | temperature, therefore low | and quartz, high silica content | | viscosity, basalt is the most | | | common | | +-----------------------------------+-----------------------------------+ | Gases are able to escape because | Gases unable to escape due to: | | they have space and time to do | | | so. | - Insufficient openings | | | | | | - Viscous magma | | | | | | - Large influx of water turns | | | into large volume of steam | +-----------------------------------+-----------------------------------+ | Occur at divergent boundaries and | Gas bubbles expand and tear the | | hotspot locations. | molten rock apart as it rushes | | | into the lower pressure | | | atmosphere, causing magma to | | | froth and erupt as hot ash. | +-----------------------------------+-----------------------------------+ | Shield volcano | Stratovolcano | | | | | Low profile | Tall cone shaped | | | | | | Convergent plate boundaries | +-----------------------------------+-----------------------------------+ | Potential energy is released as | Heat and potential energy is | | heat and kinetic energy and lava | released as kinetic energy as | | oozes out. | materials are flung into the air. | +-----------------------------------+-----------------------------------+ An effusive volcano is located under an icecap in south Iceland. A typical effusive eruption occurred first, melting the glaciers. The contact with water led to a second explosive steam eruption which led to an ash cloud being sent up into the air. #### Geological Features Fold mountains - Kinetic energy of converging plates turns into heat energy, which deforms and melts rocks (they compress to form folds and faults) e.g Himalayas Fault block mountains - Molten magma from underneath melts the crustal plates from underneath, creating tension which forces large blocks of land on the edges of divergent boundaries to rise upwards (Heat -\> Kinetic) e.g East African Rift Valley Dome mountains - Heat energy from large amounts of magma rising into crust but no reaching surface turns to potential energy of rock which is pushed up. E.g Half dome in western USA 3.3 Transformations in the Oceans, Biosphere and Cryosphere ----------------------------------------------------------- ### **Properties of Water** - State of matter - Boiling and melting point - If water boiled at lower temp, tissue of living things will be damaged. - Role as a solvent - Can have many chemicals as solutes. Creates aqueous solutions. - Surface tension - - Cohesion - force of surface tension between water molecules - Adhesion - force of surface tension between water and another surface. important during transpiration as the attraction allows water to move up. - Thermal capacity - - Temperature - average kinetic energy of particles - Thermal heat capacity - how much heat required to raise the temperature of 1g by 1 degree celsius. - Density - Ice floats and allows water underneath to flow, which helps protect living things beneath the frozen layer. Stops the creation of permanent ice blocks. ### **Production of Ocean Currents** #### Energy - Water has high thermal capacity therefore acting like an enormous heat sink which helps moderate global warming. - Heat absorbed by oceans near the equator can be distributed to the poles by ocean currents. - Cold water can move towards the warm equator through deep currents #### Salinity - When water freezes into ice in the Antarctic, it is nearly salt free. - The remaining cold water is super saline and therefore very dense. - When it reaches the bottom of the ocean it moves towards the equator. Thermohaline circulation - currents of water driven by temperature and salinity #### Water Masses - Thermocline - point beyond warm layer of water in currents where temperature drops rapidly \~ 100 metres - If warm water is moving to the poles, it must again be replaced by cold saline waters that move from deep down to the surface. This happens through 3 processes: - Tides - move back and forth, mixing deep cold water with surface waters and overtime the cold water comes up. - Upwelling - deep currents reach shallow waters near continents and are forced to the surface. These waters are oxygen and mineral rich supporting biodiversity. - Wind driven currents - Frictional forces between wind and surface water result in water movement. Trade Winds blow in a westerly direction and that's how the surface currently will move too. However, these winds are subject to Coriolis Effect, and move clockwise in the Northern Hemisphere and anticlockwise in the Southern. ### **The Global Ocean Heat Conveyor Model** - The interaction between surface and deep ocean currents in an integrated circulation system. ### ### ### ### **Effects of Global Warming** Global warming leads to an increase in freshwater in northern oceans because of melting of glaciers in Greenland (surface warming) and increased precipitation (surface freshening). This less dense freshwater could form a layer over the saltwater inhibiting thermohaline circulation, disrupting the entire circulation pattern. ### **Atmospheric Movement** #### Walker cells - Model of airflow in the tropics where air moves in a closed circuit. - Strong ocean current brings cold water northwards along west coast of South America from Antarctica (see diagram of conveyor belt) - Due to tradewinds- caused by earth\'s rotation, cold water flows westwards and is heated by the sun - Cold water undergoes upwelling on East coast of South America #### El Nino and La Nina +-----------------------------------+-----------------------------------+ | El Nino | La Nino | +-----------------------------------+-----------------------------------+ | - Warmer pacific ocean (near | - Cold water upwelling in South | | Central America) | America | | | | | - Pressure increases at | - Increased tradewinds moving | | Australia | West | | | | | - Convections shifts Eastwards | - Warm body of water travels to | | | Australia | | - Dry, sometimes drought like | | | conditions in Australia (less | - Increased precipitation and | | rainfall) | humidity in Australia | | | | | - Deep thermocline in America | - Deep thermocline near | | | Australia | +-----------------------------------+-----------------------------------+ #### Australian Monsoon - The northern Australian monsoon season generally lasts from December to March. It is associated with the inflow of moist west to northwesterly winds into the monsoon trough, producing convective cloud and heavy rainfall over northern Australia. - Definition from ABS #### Indian Ocean Dipole   ### **Relationship Between ENSO and IOD** --------------- -------------------- -------------------- ------------- Positive IOD (dry) Negative IOD (wet) Neutral IOD El Nino (dry) Very dry Neutral Dry La Nina (wet) Neutral Very wet Wet Neutral Dry Wet Neutral --------------- -------------------- -------------------- ------------- ### **Changes in the Cryosphere** Module 4 Human Impacts ====================== 4.1 Water Management -------------------- ### **Factors affecting distribution of water on Earth** - Latitude - Climate - Temperature - Topography ### **Water Pollution** Water pollutants: - Oxygen-demanding substances - organic material feeds growth of microbial decomposers and reduces dissolved oxygen for aquatic plants and animals - Pathogens - disease causing organisms e.g parasite - Synthetic organic compounds- - oil spills float on water and prevent light penetration for photosynthesis and cover shoreline food supplies. Kills animals. - Nutrients - Favors weed species over native and promotes algal bloom. - Inorganic chemicals - Pesticides and herbicides containing heavy metals lead to diseases / skeletal malformation - Sediments - during floods, water becomes brown and murky - Radioactive substances - radiation damages DNA - Thermal discharge - water used as coolant by industries gets disposed and the warm water suffocates plant/animal life. Sources of water pollutants: - Sewage - Industrial waste - Garbage/refuse - Agriculture ### **Water Treatment Methods** ### **i.Industrial waste water** 1-Wastewater sent to clarifier → solids settle and sent to landfill 2\. Anaerobic sludge digestion (without oxygen) → converts remaining organic waste to methane gas → burnt - used as energy source (biogas) 4\. Remaining solids removed via floatation and are skimmed off 5\. Biofilm → bacteria digests remaining organic material 6\. More stages of clarification as needed 7\. Solid wastes→ go to landfill \*Backwash water and reverse osmosis concentrate → sewer ### **ii.Sewage recycling** 1. Screens/ filters remove solids and grit → disposed into landfill 2. Microorganisms digest organic material → sludge removed → bacteria to further digest material → dewatered → remaining water goes through the same process 3. Filtered and chlorinated to kill microorganisms 4. Water is then dechlorinated and pumped to storage tanks ### **iii.Storm water** 1. Beach catchment filtration system 2. Pipe filters remove sediment, heavy metals, hydrocarbons and phosphorus. 3. Pollutants are macerated and sent to ocean waste → leftover water is then sent to the next stage 4. UV treatment for pathogens and fine particles 5. Treated water sent for toilets, irrigation and cleaning ### **Benefits of water conservation/recycling** 1. Less chance of water restrictions during drought 2. Reduces need to construct new dams 3. Reduces impact of urban development ### ### **Human Impacts on Water Supply** #### Directly (over extraction) Groundwater is crucial to maintain the ecosystem. However, fracking used in mining of coal seam gas consumes large volumes of it and reduces water pressure in the aquifer which has a big domino effect. #### Indirectly (algal blooms) - Eutrophication is a process where nutrients become concentrated in waterways, usually due to fertilisers/detergents entering waterways through runoff. - The excess food source for cyanobacteria such as algae, and the fact that it grows on the surface of water where light is plentiful, allow the population to thrive. - This population boom prevents sunlight from penetrating deep into water and consequently killing the bottom dwelling aquatic plants such as coral. - Their decay depletes oxygen levels in waterways and gives an unpleasant smell and discoloured appearance. - Toxins cause rashes on humans and kill mammals drinking it. 4.2 Salinity and Erosion ------------------------ ### **Salinisation** Is a build up in salts in soil and water t0 levels that impact humans and natural assets. Natural and human assets→ plants, animals, aquatic ecosystems, water supplies, agriculture and infrastructure Types of irrigation → natural salinity → dryland salinity → irrigation #### 1.Natural salinity - Seepages and scalds where salt comes up to the surface - Occurs due to: - Weathering of rocks and ancient inland sediments - Salt spray from oceans #### 2.Dryland salinity - A result of human interference - Due to land clearing for grazing- deep rooted plants being removed and replaced by shallow rooted plants - Leaves increased levels of salt in arid to semi arid land - Water table rises to the surface to reach the shallower roots - Plants that aren't salt tolerant die as the land becomes more saline #### 3. Irrigation - Excessive watering increases water table - bring dissolved salts up to the surface, increasing salinity of the soil ### **Impacts of Salinity - know a few** 1. Increased soil erosion due to reduced vegetation cover results in loss of soil structure and nutrient degradation 2. Impacts ecosystems by killing native vegetation -\> loss of food and habitat for animals 3. Increased salt content in streams and rivers create problems for human water supplies and irrigation 4. Increased risk of damage to infrastructure and water supplies 5. Loss of productivity of agriculture as salinity decreases the water and nitrogen uptake of plants. ### **Prevention of Salinity** - Deep-rooted crops (important -\> solution for murray darling basin salinity increase) - Lucerne (alfalfa) keeps the water table low AND it\'s a legume which increases nitrogen levels and soil fertility. - Limiting irrigation - Licence needed to irrigate land based on soil/groundwater levels - Alternative irrigation methods - INSTEAD OF flood and channel irrigation, trickle or drip methods use less water and introduce it to the root zone only. - Stop clearing and plant trees - Higher transpiration rates lower water table ### **Rehabilitation Strategies of Salinity Affected Soil** [Case study] Rye Park, NSW (EXAMPLE OF SALINITY AFFECTED AREA) - Higher water table -\> High salinity in soil -\> Salt scalds and low veg cover -\> risk of soil erosion by wind and water -\> land cannot be used for agriculture AND natural veg suffer -\> impacts whole ecosystem. Strategies used - Fencing off paddocks affected by scalds and planting them with salt tolerant plants - Increasing number of paddocks and rotating cattles to allow regeneration of vegetation cover ### **Soil Erosion** +-----------------------------------+-----------------------------------+ | Causes of soil erosion | Strategies to reduce and repair | | | erosion | +-----------------------------------+-----------------------------------+ | Wind - | - Planting tree breaks to slow | | | wind speed. | | - Major vegetation like trees | | | helps stop winds | - Appropriate pasture grasses | | | planted | | - During drought, grasses die, | | | and soil is exposed | - Cattle rotation to ensure veg | | | cover | | - Human activity: deforestation | | | and overstocking animals | | | heavily reduces pasture | | | levels | | +-----------------------------------+-----------------------------------+ | Water - | - Contour ploughing (across a | | | slope rather than down a | | - Overstocking, ploughing or | slope) | | infestations can leave soil | | | bare and prone to gully | - No tillage farming - planting | | erosion from heavy flooding | in narrow slit trenches | | | | | | - Ensuring veg growth through | | | stock rotation and not | | | overstocking | +-----------------------------------+-----------------------------------+ | Agriculture - | - Minimal ploughing - leaving | | | stubble after harvest and | | - Clearing of land and | chemicals to destroy weeds | | ploughing of fields | | | | - Replanting trees | | - Human and animal presence | | | destroy veg in sensitive | - Contour ploughing | | areas such as river banks | | +-----------------------------------+-----------------------------------+ | Urbanisation - | - Silt traps are legally | | | enforced (hay bales, | | - Excess sediments wash into | temporary plastic barriers) | | local streams. This causes | | | blocked channels, causing | - Permanent silt traps and | | changes in waterflow and | waterflow barriers | | washing rubbish and chemicals | | | into streams. | - Veg cover on road cuttings | | | etc. | +-----------------------------------+-----------------------------------+ ### **Soil Contamination** Heavy metals: #### Mercury #### Radium #### Lead #### Cadmium 4.3 Effects of Introduced Species --------------------------------- There are several examples of introduced species and these include: ### **Salvinia and Lantana** ### **Cane Toads** Introduced to control destructive beetles in Queensland\'s sugarcane crops. High rates of reproductions lead to infestation of cane toads in Queensland ### **Rabbits** - They are very economically damaging as they are not only invasive but cause damage to the soil by digging burrows - Erosion of land when they dig burrows - Eat crops grown in agriculture. - Loss of biodiversity due to overpopulation of rabbit species (high rates of reproduction and competition with native animals for habitat) Human activities favouring the introduced species: - Deforestation and removal of deep rooted trees encourages the growth of rabbit populations as it makes it easier for them to dig burrows and create a habitat for themselves. - Rabbit proof fencing made of barbed wire to keep rabbits out of crops grown on an agricultural scale. - Biological control (myxomatosis) - Fumigation - method of pest control that involves covering an area of land with suffocating/poisonous gas ### **Foxes** Skills ====== - When identifying trends, be specific! -\> use dates, state whether rapidly/slowly increasing/decreasing +-----------------------+-----------------------+-----------------------+ | | Experiments | Secondary Sources | +-----------------------+-----------------------+-----------------------+ | Accuracy | sensitivity of | \- the information | | | equipment | can be substantiated | | | | in more than one | | | close to the true | reliable source | | | values | | | | | | | | can be | | | | substantiated in | | | | secondary sources | | +-----------------------+-----------------------+-----------------------+ | Reliability | \- Repetition in | not biassed | | | method -\> determines | | | | reliability | written by | | | | qualified person | | | \- Control variables | | | | -\> improves it | reputable site, | | | | i.e..gov.edu | | | | | | | | current (check | | | | date) | | | | | | | | refers to data and | | | | statistics from valid | | | | first-hand | | | | investigations | +-----------------------+-----------------------+-----------------------+ | Validity | measurements are | gathered using | | | measuring what you | appropriate methods | | | intend them to | | | | measure | relate to the | | | | hypothesis or problem | | | suitable equipment | | | | | | | | controlled variables | | | | appropriate measuring | | | | procedures8th | | +-----------------------+-----------------------+-----------------------+