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Handout 14 of 14

(Topic 5.3)

Sustainable Future

Average sea surface temperature (July 2006). Global warming is causing the polar ice sheets to melt at an increasing rate. Satellite imagery is used to monitor Earth temperatures and the changes they cause to the biosphere.

Image: http://earthobservatory.nasa.gov/Observatory/datasets.html

http://earthobservatory.nasa.gov/Observatory/datasets.html

The Impact of Human Activities on the Earth Sustainable Future

Key Ideas Intended Student Learning The management of geological resources is necessary to ensure that the needs of present and future generations are met.

Understand that renewable resources may be diminished or sustained over time.

Understand that non-renewable resources may be exhausted over time.

Discuss the sustainability of the following resources:

Metallic resources Uranium Non-metallic resources Soil Fossil fuels Water Atmosphere Oceans.

Discuss the relationship between the resources listed above and their classification.

Understand the need to manage the use of these resources to ensure a sustainable future.

Discuss the need for, and limitations of, alternative sources of energy.

Describe the principles and limitations of geothermal energy.

Describe the following exploration techniques for finding metallic deposits:

• Geophysical surveys (magnetic and gravity) • Geochemical surveys.

Explain how seismic surveys are used in petroleum exploration.

Describe the requirement of the Aboriginal Heritage Act 1988 (SA) or its Northern Territory equivalent that Aboriginal sites must be regarded in the exploration for and extraction of minerals.

Describe, with the aid of diagrams, the essential features of the following mining activities:

• Open-cut • Underground • In situ leaching.

Explain how petroleum is extracted from the Earth.

The exploration and extraction of geological resources have an impact on the natural environment.

Compare the economic and environmental impacts of coal and nuclear power plants for generating electricity.

Discuss the possible effects that the exploration for, and the extraction of, geological resources can have on the environment.

Topic 5.3 Sustainable Future of 70

Sustainable Future – Cont. Key Ideas Intended Student Learning

Companies that operate extractive industries are required by law to minimise environmental damage during operations, and to rehabilitate the site when these operations cease.

Identify the key features that must be addressed by companies producing environmental impact statements.

Understand the aims of a progressive rehabilitation program for an extraction site.

Discuss possible rehabilitation procedures required by government regulations, including:

• the stabilisation of slopes; • revegetation; • visual impact.

Describe the operations and environmental management of an extractive industry visited.

Human activities can degrade the soil. Describe and explain how human activities can cause erosion and changes in salinity.

Discuss measures that can be undertaken to reduce the salinity and erosion of soil, and assess their effectiveness.

Human activities can affect groundwater, atmosphere, and oceans.

Describe how usable groundwater supplies can be affected by human activities.

Discuss the management of groundwater in terms of water-table recharge and the nature of the aquifer.

Describe the use of aquifer storage and recovery as a means of conserving water.

Discuss the possible relationship between human activities over the past 200 years and changes in the levels of one of the following atmospheric factors:

Carbon dioxide Temperature Methane Sulfur dioxide. Ozone

The sections of the Intended Student Learning that are italicised must form part of the fieldwork or practical materials submitted for moderation. They will not be examined in the public examination


5.3 – Sustainable Future SUSTAINABLE FUTURE Management or Resources

Geological resources must be managed, to ensure that the needs of present and future generations are met. Renewable Resources

Some geological resources are described as renewable, and with careful management should last indefinitely.

Some examples of renewable resources are:

• soil — it is continually being formed by weathering of rocks. • atmosphere — gases such as oxygen, nitrogen and carbon dioxide

are continually being recycled by living organisms and natural processes, such as weathering of rocks.

• water circulates through the oceans, atmosphere, living organisms and rocks by means of the hydrologic cycle.

These renewable resources may be diminished or sustained over time. For example, extensive soil erosion diminishes Earth’s total quantity of soil. The atmospheric composition may change or become polluted so that it no longer supports life. Water in rivers, lakes, rock strata or the ocean may become polluted or saline, and therefore unable to support life (especially complex organisms).

To ensure a sustainable future, these resources must be carefully managed. Soil erosion and air and water pollution must be prevented. Non-renewable Resources

Other resources are non-renewable. These took millions of years to form, and cannot be replenished as fast as they are being used. Very approximately, humans are expending in one year the amount of fossil fuel that nature took a million years to produce. These non-renewable resources will eventually become exhausted, or become too costly to produce for most uses (i.e. uneconomic to exploit).

Some examples of non-renewable resources are metallic ores, uranium, fossil fuels, and non-metallic resources such as construction materials. All these substances are physically removed from Earth’s crust and cannot be replenished.


Use of metallic resources can be managed by recycling metals, while some construction materials can be re-used or recycled. However, fossil fuels once burned are gone forever, and therefore alternative energy sources must be developed.

The graph below shows known and predicted trends in Australian oil supply and demand from 1980 to 2005.

As seen in the graph, oil production from existing developments and known discoveries are decreasing. New discoveries are not increasing, but will be insufficient to bridge the gap between supply and demand. Increasingly, Australia will be increasingly dependent on imported fuels. Alternative Energy Sources Alternative, renewable energy sources have several advantages over fossil fuels. They are enormous and inexhaustible, produce little or no pollution or hazardous waste, and pose few risks to public safety. However, presently most of them are expensive to construct, although cheap to run. Their main use is to generate electricity. Presently no alternative to the use of fossil fuels for transport is likely to be developed in the foreseeable future. Existing and predicted use of alternative energy sources is not expected to contribute more than a few % to the world’s energy supplies.

Important examples of alternative energy sources include solar energy, wind power and geothermal energy. 1. Solar Energy

Solar technologies have considerable potential since they can provide both electricity and heat. Home heating systems, solar water heaters, and cells that generate electricity are beginning to be commercially viable. Most solar technologies are much less expensive than they were a few years ago, and are likely to become even more competitive in the future.


However, solar technology has several limitations:

• The sun does not shine all the time, and hours of sunlight are generally less in areas of high population than in sparsely populated regions. Batteries must be used to store the energy collected, and these are both very expensive and inefficient.

• As shown in the diagram below, very large solar panels are needed to collect enough energy for most applications. These are very expensive to construct and install.

From The World Book Multimedia Encyclopedia (TM) (c) 1996 World Book, Inc., 525 W. Monroe, Chicago, IL 60661. All rights reserved. Advanced Photovoltaic Systems

Solar cells are useful in remote areas for specialised uses, such as operating telephones or navigation beacons for ships. Electricity for the resort at Wilpena Pound (Flinders Ranges) is generated by solar cells. The South Australian Museum obtains its electricity from solar panels and provides some electricity for the general system. In South Australia, subsidies are available for householders and communities that wish to install a solar system for generating their own electricity and selling excess power to the local grid.

Notwithstanding, solar cells are not likely to provide a significant proportion of our electricity in the short to medium term. 2. Wind Power

Increasingly popular as alternative sources of energy, wind turbine generators produce electricity by harnessing the wind. These generators are much less harmful to the environment than other sources of energy; however, wind turbines are not always practical because they require average wind speeds of at least 21 km/h. The photograph shown below is a wind farm in California that contains over 4000 separate turbines and


provides enough electricity to power the entire Coachella Valley in southern California.

A single wind-powered turbine, such as the one in use at Coober Pedy can only generate enough electricity for about 40 homes.

A wind farm has recently been constructed at Cape Jervis, and more are planned for other areas of South Australia. 3. Geothermal Energy

The geothermal gradient is the curve showing the rise in temperature with increasing depth of rock below Earth's surface.

Geothermal energy is heat energy stored below the ground.

Since the temperature of the rock rises with increasing depth, underground water (water circulating in pores and crevasses in the rocks) is also hot.

Geothermal energy is attractive because it has a low impact on the environment; however, there are few sites where geothermal energy can be extracted economically.


Existing Use of Geothermal Energy

Existing use of geothermal energy is confined to a few volcanic and recently volcanic areas of the world (e.g. near Rotorua, in the North Island of New Zealand) where:

a. the rocks close to the surface are very hot, and

b. there is a good supply of circulating groundwater which is hot enough to produce steam, i.e. the water temperature at < 3 km below the surface is > 150° C.

Hot water forms as steam near the surface and is piped under pressure and used to drive turbines for generating electricity. This is a very inexpensive method of producing electricity.

Source: http://en.wikipedia.org/wiki/Geothermal_power

Although geothermal energy can be considered as a renewable energy source, it is not unlimited. Limits have recently been placed on the use of geothermal hot water and steam in the area of Rotorua (NZ) because excessive use was causing a decrease in the height and activity of the geysers in the area — a valuable tourist attraction. Plans to build a second geothermal power station were scrapped several years ago.

4. Geothermal Energy from Hot Dry Rocks

South Australia is at the forefront of research and development into geothermal energy from hot dry rocks (HDR). In 2002 Geodynamics Ltd registered on the Australian Stock Exchange. Its business is to explore and develop HDR geothermal energy from deep within the Cooper Basin (northeast SA) and the Hunter Valley (NSW).

“HDR geothermal energy relies on existing technologies and engineering processes, and is the only known source of renewable energy with a capacity to carry large base loads.” Source: http://www.geodynamics.com.au/IRM/content/02_hotdryrock/02.html


In the Cooper Basin, heat from Carboniferous “hot” granite (i.e. granite with anomalously high uranium content) is trapped within the basin at depths of around 3.5 to 5 km. Heat is extracted from granites by circulating water through the artificially and naturally-fractured granite which has a temperature of more than 250° C. Water is pumped (via injection wells) into the fractured granites and then extracted (via extraction wells). On the surface, conventional power stations convert the heat energy in electrical energy. HDR geothermal energy is considered to be both “clean and green” and the Cooper Basin has the potential to become the world’s largest geothermal field. For more information on HDR geothermal energy visit:

http://www.geodynamics.com.au http://www.pesa.com.au/publications/pesa_news/feb_05/pesanews_7409.html

EXPLORATION FOR GEOLOGICAL RESOURCES

The copper deposits at Moonta (Yorke Peninsula) were discovered in 1861 by a shepherd (Patrick Ryan) who found several pieces of malachite that had been unearthed by a burrowing wombat. However, but the days of this kind of accidental mineral discovery are long gone.


The extent of the world's ore deposits is minuscule compared with its total surface area. To search for and discover new deposits requires a range of increasingly specialised (and expensive) techniques. Even large deposits such as Mount Isa and Broken Hill are less than 10 km2 in area — less than one millionth of the area of the Australian continent. The ore bodies at Mount Isa and Broken Hill had recognisable surface outcrops, as did most of the deposits that are presently mined. In the future, most discoveries will be made at great distances below Earth’s surface, perhaps buried by hundreds of metres of barren rock.

The Olympic Dam Cu-U-Au-Ag deposits are 500 m below the surface and they were located using the techniques described in the following paragraphs.

Exploring for mineral deposits is both expensive and time consuming. In 1983, typical expenditure on exploration to find a major deposit of a base metal deposit was $30 million. Ten to twenty years may elapse between the start of a search and discovery of a deposit. Developing the deposit also takes many years. The deposits at Olympic Dam were discovered in 1975; however, copper and uranium were not produced for sale until 1989, representing a lead time of 14 years between the discovery of the deposit and the first sale of material from the site.

Above: Drilling for uranium on a gibber plain approximately 10 km west of the Beverley Uranium Mine. This bore encountered economic grade mineralisation within a 40 Ma palaeochannel (on an alluvial fan) at about 100 m. Future discoveries of mineralisation will be made in the subsurface where there is no indication of mineralisation. Methods of Investigation

Mineral exploration can be divided into three types of activity — geological, geophysical and geochemical; however, the final assessment combines the outcomes of all three. Geophysical and geochemical techniques are based on the fact that high concentrations of metallic and non-metallic minerals chemically and physically affect the properties of the rocks that surround them. Interpretation of variations, or anomalies, in these chemical and physical properties enables the deposits to be located. Metallic ores usually occur in very old rocks. For example, in


South Australia, copper and other metalliferous deposits occur in, or are associated with Precambrian rocks. Geophysical Exploration

Geophysical techniques are generally used for one of the following purposes:

1. To search directly for hidden ore deposits.

2. To search indirectly for minerals or petroleum by looking for a set of geological conditions known to be favourable for accumulation of these resources. An example is the search for anticlinal traps in petroleum exploration.

3. As mapping tools to provide information on rocks in areas where the relevant geology is concealed by younger material.

Exploration geophysicists measure the physical properties of the crustal rocks, such as their elasticity, gravity, magnetism, radioactivity or electrical properties. Normally the measurements are made at equally spaced intervals over a traverse line or at equally spaced grid points over the area under investigation. The results may be displayed as contour maps. Some measuring devices may be operated from aircraft, land vehicles or ships. Other devices may be lowered into drill-holes.

Source: http://en.wikipedia.org/wiki/Image:NASA-Flinders-Ranges.JPG

The first stage of exploration normally involves reconnaissance from the air and satellite imagery available from Landsat 7 (these are false colour images). The photographic image above is of the northern Flinders Ranges at an altitude of approximately 100 km. Photographs and Landsat images should be compared with published geological maps (e.g. COPLEY and


PARACHILNA) prior to and after airborne geophysical data is acquired. Photographic data are available at relatively low cost from government agencies (i.e. PIRSA) and can be overlain upon magnetic and gravity data using GIS computer programs (e.g. MapInfo).

Magnetic Surveying

Measurements of Earth’s magnetic field reveal that, on a local scale, the field is not uniform. It consists of a series of relative highs and lows corresponding to variations in the magnetic properties of the rocks in the upper part of Earth's crust. Valuable information about the distribution of different rock types and the structural relationships between them can therefore be gained from these measurements.

Airborne magnetic surveying, using a magnetometer, involves measuring variations in the strength of Earth's magnetic field to produce regional magnetic contour maps and magnetic profiles which indicate depths of basement rocks or minerals of contrasting magnetisation.

Magnetic or iron-rich minerals, such as magnetite, may be present in metal deposits, and give rise to magnetic anomalies, which may justify further testing. For example, the copper and uranium deposits at Olympic Dam are embedded in a haematite matrix. A magnetic survey therefore assisted in the discovery of the copper and uranium, although these minerals are non-magnetic. Presently the haematite in the Olympic Dam cannot be economically processed. Therefore, it is stored in tailings dams until suitable processing techniques become available.

Promising results from an aerial survey may be followed by ground magnetic surveys, giving more detailed information about a smaller area. Gravity Surveying

The value of Earth's gravitational attraction (g) varies from place to place. The density of the underlying rock is the main cause of these variations. Dense metal-rich rocks give rise to a positive gravity anomaly as the value of g will be higher than in the surrounding area. The changes are


extremely small, but can be measured by sensitive instruments, such as a Bouguer gravity meter.

Like magnetic field measurements, gravity measurements are done on a grid basis; first from the air and then followed by detailed ground surveys over promising areas.

The diagram below shows how a concentration of metallic minerals may give rise to both magnetic and gravitational anomalies. Geochemical Exploration

Geochemical exploration is conducted by collecting samples of soil or stream sediment and analysing them for trace metal content. There is a normal concentration of metallic ores in the rocks of any area, as trace minerals. This is called the 'background' and may be about 50 ppm.

A mineral deposit (e.g. sphalerite) may, after weathering and erosion, produce a 'halo' of zinc concentrations higher than the background level, in the nearby soil or downstream sediment. A geochemical survey may detect this halo as an anomaly. Values could be, for example, 200 to 1000 ppm (parts per million) in an anomalous halo. Anomalies indicate areas worth more detailed investigation by other survey methods and by drilling.

The diagrams below show how a nickel sulphide rich layer of rock affects the concentration of nickel in the soil above it.


A geochemical survey may be undertaken in two stages. Firstly stream sediment or water samples are collected and analysed to locate the area of interest.

This area is then subjected to detailed soil sampling to precisely locate the anomalous zone.

Seismic Surveys

Seismic surveying, or vibroseis, is of particular value in petroleum exploration, since it indicates the locations of possible oil traps, such as anticlinal structures. A thumper truck produces sound waves. The waves travel into the subsurface and may be partially reflected back to the surface when they reach a boundary between two rock formations. Devices called geophones detect the reflected waves. A second truck holds a seismograph, an instrument that records the time in which underground rocks reflect the waves to the surface. By measuring the arrival times of the different reflected waves, it is possible to determine the positions of boundaries between different rock types. The process is repeated at closely spaced intervals along lines crossing the area being explored. Cross-sectional diagrams can then be produced showing the structure of rocks below the surface. This process is shown in the adjacent diagram.

From The World Book Multimedia Encyclopedia (TM) (c) 1996 World Book, Inc., 525 W. Monroe, Chicago, IL 60661. All rights reserved. World Book illustration by Steven Liska


Drilling

Geological mapping, followed by geochemical and geophysical surveys, may indicate that a particular area could contain an ore body or an oil field. An area where different types of anomalies coincide would seem particularly promising. The cheapest and quickest method of further exploration is a diamond drilling programme to obtain core samples, which can be further analysed. Pattern drilling of the most promising area for core sample analysis will provide information about the grade of the ore, as well as the total reserves and the shape and depth of the ore body.

Eventual mining will depend on many factors such as the size, grade, depth and location of the deposit.

Petroleum source rocks are usually shales of Palaeozoic to Palaeogene age. However, in Australia, many, if not most petroleum source rocks are coals (e.g. offshore Gippsland Basin). ABORIGINAL HERITAGE ACT (1988)

The Aboriginal Heritage Act of 1988 provides protection for all aboriginal objects, remains, sites of spiritual, archaeological, anthropological and historical significance, whether registered or not. A person runs the risk of a substantial fine if items of Aboriginal significance are damaged or destroyed. The main features of the act are as follows:

• Protection of all sites and objects of significance to aboriginal tradition, archaeology, anthropology or history.

• Provision for traditional owners to determine whether land or objects are of significance to Aboriginal heritage.

• Provision for traditional owners to be delegated, at their request, key functions under the Act, including the authority to damage or disturb sites and to approve the sale of Aboriginal objects.

• Provision for developers and the public to seek a determination from the Minister as to whether an area or an object is of significance to Aboriginal heritage.

• The establishment of an all Aboriginal advisory committee on Aboriginal Heritage to advise the Government on state-wide Aboriginal heritage interests.

• Access by Aboriginal people to sites on private land to carry out traditional activities.

• An Aboriginal heritage fund. • Provision to acquire sites.


Obviously, the Aboriginal Heritage Act (1988) as well as Aboriginal land rights legislation and landmark High Court decisions (e.g. Mabo, Wik) impact significantly on exploration and exploitation of natural resources. EXTRACTION PROCESSES

Although many factors must be considered when selecting a method of mining a deposit, the most important factor is the nature of the deposit. In some cases it may eventually be necessary to change from one method to another, for example from open-cut to underground if the deposit becomes too deep. Recently BHP Billiton applied to SA state authorities to expand the underground Olympic Dam project into an open-cut mine up to 6 km across. Clearly the development of an open-cut mine at Olympic Dam has become feasible largely due to major increases in the price of Cu, U, Au and Ag on the world market since the year 2000. Open-Cut Mining

If the mineral deposit is on or near the surface, open-cut mining techniques may be applied. They have the advantages of natural ventilation and light. They may be adopted for working very small deposits, such as road aggregate quarries, or for very large ones, such as the iron ore mines in the Hamersley area, Western Australia. Open-cut mining is not always convenient, and is affected by weather conditions such as high rainfall. Flooding and environmental degradation associated with the Bougainville (Papua-New Guinea) copper deposit in the 1990s demonstrates that open-cut mining can be compromised by rain and weather. Other environmental problems such as noise, dust and waste disposal are associated with this method of mining. Nevertheless, by far the greatest tonnage of material is recovered by surface mining methods.

Ore bodies most suitable for open-cut mining are shallow deposits that extend more or less horizontally. Obviously the amount of overlying rock, or overburden, which must be excavated, is an important factor in the profitability of a mine.

Most open-cut mines are in the form of benches, which provide a working area for drilling crews, an area both to store broken ore, and to load it into trucks. Benches also provide safety in case of slope failure and as a means of transporting mined rock.


The adjacent diagram shows some benches in an open-cut mine.

The diagrams and graph below illustrate the problems associated with open-cut mining of ore bodies that are not horizontal. The volume of overburden increases as the deeper ore is mined. The area of land occupied by the mine also increases as the deeper ore is extracted.

The adjacent graph also illustrates the relation between volume of ore and volume of overburden as the depth of the pit increases.


Eventually open-cut mining of the deposit may become uneconomic, and the company must decide whether to proceed with underground mining

If necessary, explosives are used to break up the material to be extracted. Trucks or conveyer belts then convey it to crushers. Further treatment depends on the nature and purpose of the material. Underground Mining

Underground mining is more expensive than open-cut mining, so it is uneconomic for low-grade or low-value deposits. It may take many years to develop an underground mine before production can begin.

The diagram below shows, much simplified, the essential features of a typical underground mine.

Access to the deposit is gained by means of a vertical shaft. Machinery in the winding house operates the lifts, which take the miners down to the ore body and bring crushed ore to the surface. A series of drives provide access to the ore body at different levels. When sufficient development of shafts, drives etc has been completed, stoping, or removal of the ore can begin.

The mine must also contain one or more ventilation shafts, so that the miners have access to fresh air. It may also be necessary to continually pump the groundwater out of the mine.

The adjacent photograph shows the Whenan Shaft at Olympic Dam which brings some of the ore to the surface.

Some modern mines, such as Olympic Dam have a decline as well as a shaft. This provides vehicles with access to the mine.

At Olympic Dam, the ore may be brought to the surface via either the shaft or the decline. Here, as in open-cut mining, the ore is removed from the rock face by blasting. It is then crushed before being hauled to the surface for processing. Coal in open-cut mines is mined somewhat differently; it is removed by huge cutters, which move along the seam.


In Situ Leaching

The mining technique of in situ leaching (ISL) involves circulation of solutions through an ore-body to dissolve the mineral of interest in the ground, from where it is pumped to the surface and recovered in a processing plant.

The ISL technique is generally suitable for small or low-grade ore deposits that would otherwise be uneconomic to extract using conventional open-cut or underground mining techniques. However, before ISL can be considered, the deposit must be shown to be within an aquifer which is isolated from other aquifers or groundwater users.

The process of ISL is typically applied to uranium and copper deposits. The Beverley, Honeymoon and Goulds Dam uranium deposits (east of the Flinders Ranges, SA) are examples where the uranium ore exists in a water-saturated sandstone aquifer. At Beverley, to recover the uranium ore (yellowcake: U3O8) boreholes are drilled to a depth of around 100 m. Two kinds of boreholes are drilled – injection wells and extraction wells. Sulphuric acid (H2SO4) and hydrogen peroxide (H2O2) are mixed with water and introduced into the aquifer via the injection wells. H2SO4 lowers the pH of the aquifer and H2O2 oxidises the uranium minerals (uraninite and coffinite) which form coatings around sand grains, thereby making the uranium soluble. The solution containing uranium is then pumped back to the surface via extraction wells and the uranium is recovered in a processing plant that recycles the sulphuric acid and any hydrogen peroxide still in solution. This method of mining never recovers all the uranium mineralisation, but estimated recoveries of up to 80% have been achieved at Beverley.

A typical ISL well-field is shown schematically in the diagram below. It uses a series of injection and extraction wells to control the movement of solution. A pattern known as a “5-spot” is most often used, where one extraction well is surrounded by 4 injection wells. The distance between these injection wells is usually 15 to 30 m.

Solution


In order to ensure an economic uranium recovery rate and to prevent the escape of highly corrosive and toxic solutions into the wider environment, it is necessary to have very tight controls on the flow of the solutions through the aquifer. This is achieved in two ways: by vertically restricting

Solution

Solution

Injection

Extraction

water flow and by always extracting more groundwater out than the amount of solution pumped in. This ensures flow towards the extraction well. The uranium-rich solution is brought to the surface processing plant. Here, it is treated with chemicals that cause the uranium to precipitate from the solution. The remaining solution is reused by injecting it underground.

Above: Injection and extraction wells at the Beverley in situ uranium mine. In situ leaching has a number of advantages over open-cut and underground mining.


• Miners are not directly exposed to the ore-body. There is reduced radon release and radiation because the ore is in solution. Therefore, there is also very little dust.

• It is less expensive to operate because large volumes of rock need not be broken-up and removed. There are also shorter lead times to production and it is quicker to produce an end-product.

• There is no solid waste. Waste is confined to evaporation ponds. • It is less costly to build because it does not need the expensive

infrastructure of open-cut and underground mining, i.e. shafts, tunnels, crushers.

• There is much less ground disturbance. There are no open-pits, shafts, tunnels, earth moving equipment or grinding and crushing facilities. ISL operations take up less land and therefore there is less visual impact.

• There is less rehabilitation required because there is less ground disturbance. Upon completion of mining, wells can be sealed and capped, process facilities removed and the surface returned to its original contour and vegetation.

• Smaller, lower grade and narrower ore bodies can be mined. • The deposit can be developed without destroying the aquifer.

However, because there is a risk of radiation in the extraction process, safety procedures are embodied in all in situ leach mine operations.

Above: Processing plant at the Beverley mine. Here the solution containing sulphuric acid and dissolved uranium is separated and the clean acid returned to the well field. Topic 5.3 Sustainable Future of 70

Extraction of Petroleum

Petroleum may be extracted from either on-shore or off-shore wells.

Off-Shore Wells

Most of Australia’s oil and gas is found in the oceans that surround the continent. The Gippsland Basin in Bass Strait and the North West Shelf off the coast of Western Australia contain the major fields. Offshore platforms support the drilling and extraction equipment. The oil is piped to the shore by pipelines on the ocean floor.

The pressure of overlying rocks, and of the water below the trapped oil or gas, influences how oil will flow from a reservoir. In Bass Strait, oil and gas (and the water with which it is trapped) move into the wells under pressure from a strong natural flow of underground water. A team of geologists and engineers calculates how many wells will be required. They decide exactly where to drill to extract the maximum amount of oil and gas.

0 m

500

1.5

1 km

2 km

On land, single wells can be drilled at different locations over a petroleum field. However, for off-shore wells, because of the high cost of production platforms, a single location is often used to recover the hydrocarbons from an entire field. In directional drilling, an oil well is drilled at an angle rather than straight down, so that many wells can be drilled directionally from one platform. On-shore Wells

An on-shore oil well consists essentially of a borehole extending into the oil-bearing layer of reservoir rock, as shown in the diagram below. A pump on the surface pumps the recovered oil into holding tanks, from which it is transferred to the treatment plant. The Moomba area (northeastern SA) has many such oil wells, all of which are connected to the main Moomba plant.


Oil and gas occur as droplets of fluid in the pore spaces between the particles of the reservoir rock. The larger the pore spaces between grains (i.e. the greater the permeability), the more rapid will be the flow of liquid. Rocks with unusually large pore spaces (such as cavernous limestone) can produce enormous volumes of oil and gas. Individual wells around the Persian Gulf often produce more than 10 000 barrels per day.


When a borehole is drilled into rock containing petroleum the reservoir is opened to the atmosphere. After lining the well hole with pipes, the drilling crew lowers an instrument called a perforator into the well. The perforator punches holes in the casing through which oil can enter the well bore.

Petroleum flows into the tubing in the well to reach the surface. Pressure caused by expansion of the trapped gas, or artesian water pressure (or both) drives the oil to the surface. However, sometimes the pressure may not be great enough, and the petroleum must be pumped to the surface.

Offshore platforms vary in size, shape and type. Their design depends on the size of the field, the depth of water and distance from the shore. A steel structure on piles driven into the seabed is common. ENVIRONMENTAL IMPACTS

Extraction and exploitation of resources inevitably has detrimental effects on Earth’s environment. This is usually on a local scale, but some effects, such as air and water pollution can affect the entire planet. Exploration Phase

Environmental impacts during the exploration phase of resource extraction are obviously less than during the actual extraction phase. They are caused mainly by the infrastructure necessary to conduct the exploration program. These include removal of vegetation, construction of roads, campsites and runways for aircraft. In areas that seem promising, holes are drilled to obtain cores for testing.

Since most exploration activity fails to discover economic deposits, the impact of exploration is likely to affect large areas. Impact is especially great in arid regions where regrowth of vegetation is slow. Such is the case in most of arid and semi-arid Australia. Extraction Phase

Of course, on a local scale, the impact of actual extraction is much greater than that of exploration. The nature of the impact depends on the nature and size of the operation. Quarrying and Open-cut Mining

Both quarrying and open-cut mining results in large excavations as well as unsightly heaps of overburden (rock that was removed to gain access to be the ore body). Moreover, people living near a quarry or open-cut mine must contend with dust, and the noise of machinery, explosives and large trucks rumbling past their door. Underground Mining

The obvious benefit of underground mining is that there is no hole in the ground. However, in older mining towns such as Broken Hill and Mount Isa, large heaps of mullock (waste rock from the mines) dominate the skyline. There is also a possibility that future subsidence of worked-out stopes could damage buildings immediately above the mine.

Both these problems are overcome at Olympic Dam where mullock is returned underground and mixed with a small proportion of cement to fill worked-out stopes.

Ore Processing

Processing of sulphide ores results in formation of acid rain due to release of sulphur dioxide (SO2) into the air from smelting. An example of the effect of acid rain can be seen in the vicinity of the old copper mining town of Queenstown, Tasmania. The trees there were removed to provide the timber that was needed for mining and processing the ore. Regrowth vegetation was prevented, largely by poisonous acid rain from the copper smelter. Consequently the hillsides around Queenstown are now devoid of trees — a desert in a high-rainfall area!

Retention of tailings (portions of washed ore which are too poor for further treatment) is essential to ensure that metals do not pollute rivers or underground water. The material is placed in tailings dams, from which the water evaporates. The floors of tailings dams must be carefully constructed to prevent leakage of contaminated water into aquifers.


Effects of any Large-Scale Project

A large-scale project, such as Olympic Dam, requires the development of considerable infrastructure, including housing and other facilities for employees and their families, associated roads and railways. A clean fresh-water supply is essential, both for ore processing and for domestic consumption. Coal versus Nuclear Power

In Australia, coal, natural gas and running water supply the energy required for generating electricity. In other parts of the world, electricity is generated by nuclear power, often using uranium exported from Australia. Australia has 24% of the world’s low-cost recoverable uranium. Other areas that have substantive resources are Kazakhstan (17%), Canada (9%), USA (7%), South Africa (7%), Namibia (6%), Brazil (6%) and Niger (5%) (Source: http://www.world-nuclear.org/info/inf75.htm).

High-grade ore - 2% U 20 000 ppm U Low-grade ore – 0.1% U 1 000 ppm U Granite 4 ppm U Sedimentary rock 2 ppm U Earth’s continental crust (av) 2.8 ppm U Seawater 0.003 ppm U

Granites in Australia typically have higher concentrations of uranium (10 ppm) than the world average (4 ppm). This helps explain the fact that Australia has such a high proportion of the world’s uranium reserves.

Based on the present (July 2006) world price of uranium ($49 per pound) and the present rate of consumption, the world has a 70 year supply of uranium (in January 2001 the price of uranium was US$ 6.70 per pound). However, if all “convention” sources of uranium are considered (e.g. phosphates), the world has an estimated 200 year supply, and even more if the world price increases. It is important to realise that uranium reserves are presently low due to suppressed exploration activity during the period 1985 to 2005. It is more than likely that the present exploration boom will significantly add to the world’s uranium reserves.

In August 2006, 16% (2626 x 109 kWh) of the world's electricity was produced from nuclear power (See http://www.world-nuclear.org/info/reactors.htm for tabulated data on all countries with nuclear power generation). In 2006 thirty-one countries, continue to operate 442 nuclear reactors and, despite Chernobyl, nuclear reactors are still being built. Twenty-eight reactors are presently being constructed around the world, with another 202 reactors planned or proposed. For example, China presently operates only 10 reactors, but is building another 5, planning 13 and proposing an additional 50.

France is more reliant on nuclear power than any other nation, with nuclear energy (from 59 reactors) accounting for 79% of its energy needs. Topic 5.3 Sustainable Future of 70

Other nations heavily reliant on nuclear energy are Lithuania (70%), Belgium (56%), Slovakia (56%), Ukraine (49%), Sweden (45%), Armenia (43%), South Korea (45%), Hungary (37%), Switzerland (32%), Germany (31%), Japan (29%), United Kingdom (20%) and the USA (19%).

Therefore unlike some fossil fuels (e.g. oil), the world's supplies of uranium are assured for the foreseeable future, and nuclear power generation is becoming more popular, despite nuclear accidents such a Chernobyl (former USSR) and Three-Mile Island (USA).

Coal-fired power stations are cheaper to build than nuclear power stations, but generally more expensive to run. Their main environmental impact is production of ‘greenhouse gases’ and other air pollutants. Moreover, coal-fire power stations produce acid rain.

Nuclear-powered generators have several other advantages over generators that use fossil fuels. These include:

• They do not use scarce fossil fuels that are required for transport purposes.

• Although the reactors are more expensive to build, the cost of fuel may be less, depending on the fossil fuel situation of the country concerned.

• A very small quantity of uranium produces a large amount of energy. For example, a 30 g pellet of uranium dioxide is equivalent in energy to between 2 and 3 tonnes of coal or about 10 barrels of oil.


• Volumes of fuel needed to operate a nuclear reactor are therefore very small - minimising the environmental impact and cost of transporting fuel.

Despite these advantages, there is considerable opposition to the use of nuclear fuels and the mining and export of Australian uranium. Some of the reasons for this include:

• Problems of waste disposal. Although nuclear reactors produce a far smaller volume of waste than power stations using fossil fuels, the wastes are radioactive, and the substances involved have half-lives of many hundreds of thousands of years. Research is being undertaken to find solutions to this problem, but presently there are thousands of tonnes of used radioactive fuels in 'temporary' storage across the country and around the world.

• Nuclear proliferation. Australians are concerned that purchasers of our uranium may not use it to generate electricity, but to build a

bomb, or to conduct nuclear weapon tests — such as the 1995 French tests at Muroroa Atoll in the Pacific Ocean.

• Nuclear accidents. The dreadful devastation caused by nuclear accidents, e.g. the Chernobyl disaster caused a dramatic increase in birth defects in the area around Chernobyl and elsewhere across eastern and northern Europe. The concrete 'coffin' that was built over the reactor to contain radiation began to crack after only 5 years and will soon require a new protective structure at a cost of many billions of dollars.

The diagram below summarises the advantages and disadvantages of coal and nuclear power stations.

SOIL DEGRADATION

Two major causes of soil degradation are erosion and changes in salinity. Changes in Salinity

About 80 million years ago, much of what is now central Australia was under the sea. Consequently, the rocks and groundwater in this area contain large quantities of salt (NaCl). Human activities have caused the watertable to rise so that salt is deposited close to the surface which affects plant growth.

Two processes that cause salinity changes are discussed below. 1. Dry Land Salting

Removal of trees and shrubs increases the amount of rainfall that soaks into the ground, causing the watertable to rise. Shallow-rooted crops that are planted after the land is cleared do NOT absorb water as effectively as deep-rooted native trees and bushes. The roots of these crop plants are therefore in regions of saline water and


consequently the plants do not grow very well and the land becomes unproductive. The photograph below shows an area along the Murray River that has been degraded by salinity.

Recharge of groundwater is greatly increased when land is developed

for agriculture and under these conditions groundwater levels rise and salts are mobilised; both water and salt discharge at the surface are increased causing land and water degradation.

This effect is shown in the two diagrams below.

Before clearing, deep-rooted trees help to keep the water table lowand stable.

After clearing, more water stays in the soil, and the watertable rises. In the worst affected areas, the water table rises towards the surface (bringing with it dissolved salts).

2. Irrigation Salting

Over-irrigation of orchards, vineyards and other forms of agriculture also causes the watertable to rise, resulting in decreased productivity.

The Murray River Basin is an area severely affected by irrigation salting and raised groundwater levels due to deforestation. Groundwater pumps have been installed to lower the watertable, by pumping the saline water (from boreholes in agricultural areas) into the River Murray. Unfortunately this increases the salinity of the Murray so that downstream irrigated areas receive saline water. Consequently the lower


reaches of the Murray River are the areas where the water quality is most affected.

One third of Australia is composed of salt-affected soils. One sixth of this is a result of agricultural and irrigation practices of the last 100 years. The problems have largely emerged during the past 35 years, but they were caused by decisions made before present-day land-owners became aware of the consequences of land clearing and irrigation practices. Effects of Salinity

Salinity:

• causes land becomes unusable.

• costs Australians over $270 million a year (1999 data).

• causes native animals and plants to become endangered or extinct.

• pollutes rivers with dissolved salts, some of which contribute to the growth of poisonous blue-green algae.

It has been estimated that around 2.5 million hectares of land are affected by dryland salinity in Australia, and that there is potential for up to 12 million ha to become affected. This represents 4.5% of presently cultivated land. Increases in salinity of stream water also present a major problem. Dryland salinity is becoming a critical problem in Western Australia where 1.8 million ha of farmland is already affected by salinity, a figure that could easily double over the next 20 years.

In Western Australia, where dryland salinity is most critical, 36% of divertible surface water resources are brackish or saline, and a further 16% is of marginal quality. Moreover, all the principal agricultural districts in South Australia exhibit some degree of land salinisation and at least 20% of the surface water resources are more saline than the recommended limits for human consumption. Dryland salinity is also a major threat to land and water resources in Victoria and New South Wales, and is a primary cause of salinisation in the Murray-Darling Basin. Many townships are also affected by salinity, causing substantial damage to local infrastructure, including roads and buildings. Measures for Reducing Salinity

Management Measures

The rate of salinisation can be reduced by:

• Improved irrigation practices — using less water, using drippers instead of overhead sprinklers etc.


• Revegetation to lower the watertable, starting with salt tolerant plants such as samphire and saltbush, and eventually planting deep-rooted eucalypts and acacias.

• Planting more salt-tolerant strains of trees, vines, pastures etc. • Reducing the area under irrigation. • Retiring some farmland from use.

Structural Measures

Salinisation can be redressed by:

• Constructing wells to intercept saline groundwater and pump it away from rivers.

• Piping excess saline water to irrigation basins outside the river valley.

• Constructing dams to hold high quality water during wet seasons for release during dry seasons in order to flush salt out of the river systems.

All these solutions are expensive and long-term. There is no short-term cure for salinity.

It is generally recognised now that catchments often cannot be restored to their former condition, and those areas affected by salinity require careful management to reduce its impact and halt its spread. Replanting of native vegetation in critical recharge areas and use of salt-tolerant plants in groundwater discharge areas are possible options which are widely used, but their benefits need quantifying.

The benefits of man-made engineering solutions (groundwater pumping, drainage schemes and on-farm evaporative disposal etc) also need to be quantified. Reducing dryland salinity will undoubtedly involve combinations of both natural (vegetation) and engineering solutions to allow for short-term and longer-term sustainable agricultural development. Soil Erosion


“I dunno mate. Reckon it must have taken nature a long time to change it to this flat in the first place”

Unlike the soils of many other countries (especially northern hemisphere countries), Australia’s soils are shallow. Pioneer farmers did not realise this and farmed the soils the same as their thick, rich soils of their European homelands. In Europe, rainfall is more uniform, evaporation is significantly less, and rain falls more gently than in Australia. Early settlers were unaware of the effects of heavy downpours on dry ground after the removal of all vegetation. The results were a disaster for the land. In Australia, there is often less than 15 cm of topsoil and because these thin soils took about 30 000 years to form it is essential that we conserve them.

However, current intensive farming practices cause them to blow or wash away on a seasonal basis. On average we lose about 1 mm of topsoil each year. At this rate, most of our valuable topsoil will be blown or washed away within a few. Prevention of Soil Erosion

Soil conservation requires methods that differ from one locality to another. Firstly, it is necessary to recognise the actual and potential erosion, and then take steps to prevent it. Water erosion can be minimised by maximising the amount of rain that soaks into the soil. To minimise erosion, farmers and environmental bureaucracies must:

1. Ensure that the timing of and type of cultivation is appropriate for the climate and soil type.

2. Avoid cultivation or deforestation of steep slopes. 3. Cultivate following the contours of the land. Furrows should be

horizontal, to avoid water channelling down them to cause erosion. 4. Ensure that slopes and waterways leading to dams and creeks should

be well grassed (grass holds soil particles together and slows running water, thereby preventing gully erosion).

5. Ensure that the humus content of soil is kept as high as possible. Retain stubble after harvesting and use it as mulch (this can save up to 90% of soil loss).

Wind erosion in arid areas is often a result of over-stocking. If stock have eaten all the vegetation cover, or if exposed surface soil has been pulverised by their hooves, then dust is raised by even gentle winds. In


‘marginal’ rainfall areas where the rainfall is uncertain, cultivation for crops may cause wind erosion if the soil dries out before the crop has grown sufficiently to bind and protect it. GROUNDWATER POLLUTION

Widespread use of fertilisers and pesticides, poorly managed sewage and agricultural effluent disposal, together with industrial pollution have caused widespread contamination of groundwater by nitrate and other chemicals. This contamination has reduced the availability of groundwater for water supply and led to the pollution of rivers and estuaries.

Heavy metal and arsenic contamination of groundwater in Bangladesh and India is linked to the extensive use of groundwater for potable supplies in rural areas. This has exposed millions of people to the risk of arsenic poisoning.

In areas close to the coast, the fresh superficial groundwater may overly a wedge of salty water extending up to a kilometre inland. Excessive pumping from bores in these areas can increase the size of the saltwater wedge at the expense of the fresh water, so that the bores start to pump salty water. Once this occurs it can take decades (with no water extraction) before the system can recover. Topic 5.3 Sustainable Future of 70

MANGAGEMENT OF GROUNDWATER Two considerations are involved in the management of groundwater — quantity and quality. Quantity We need to extract water from aquifers to meet our needs for a high quality affordable water supply, and to ensure that our houses are dry and agricultural lands are not waterlogged. At the same time, we need to ensure that our natural environment is protected with enough water to maintain trees, streams and rivers, lakes and wetlands. In recent times we have come to understand that too much water can present a problem for wetlands, with rising watertables in some areas resulting in the death of lakeside trees, and seasonal lakes being turned into permanent ones resulting in the loss of animals that are specialised to survive in lakes which dry out each year (ephemeral lakes). Quality The underground location and slow movement of groundwater make it very difficult to remove pollution once it has been introduced into an aquifer. Consequently protection and prevention are the best strategies to maintain groundwater quality. Reducing the number of septic tanks in metropolitan areas, and avoiding development, especially industrial development, over important sources of groundwater are two important approaches. Management of contamination from a variety of sources is difficult because it requires changes in the behaviour in whole communities in the use of chemicals and groundwater. Significant effort is required to develop specific community-based education programs deigned to modify land use in sensitive areas. Additional research is urgently needed to manage the arsenic contamination problem in aquifers of the Indian subcontinent.

There are several types of information to be determined by a program of research into aquifer pollution. Examples include:

• sources of pollution: when, where and how much chemical is released to the environment.

• the environmental chemistry of each pollutant. • pollutant transport pathways. • impacts on ecosysems and water quality.

To provide data on groundwater water quantity and quality, monitoring bores must be constructed in several locations around artesian basins. Water levels and samples for chemical analysis must be taken at regular intervals (most commonly monthly or quarterly) to provide a growing historical record of aquifer systems. This basic information is required to


develop policies to protect groundwater supplies as well as wetlands and vegetation that rely on groundwater. Watertable recharge and the nature of aquifers

Misconception: There is a widespread misconception in the community that groundwater aquifers exist as underground rivers that flow through tunnels or caves. This is completely untrue (with the exception of very few areas on Earth with karst limestone geology).

The truth: most of Earth is covered with sedimentary rocks. Sedimentary rocks – sandstones and limestones – are porous, much like a sponge. In the subsurface, water (or oil and gas) fills these pores. In many (moderately cemented) rocks the pore spaces are interconnected thereby allowing fluid to flow through the rock – such a geological system is called an aquifer.

Source:

http://en.wikipedia.org/wiki/Image:Groundwater_flow_times_usgs_c

ir1139.png

Note: the Great Artesian Basin (GAB) which occupies much of central Australia and western Queensland is recharged along the Great Dividing Range that runs along Australia’s eastern coast. It has been calculated to take 2 million years for water to flow underground (through the GAB aquifer) from the western slopes of the Great Dividing Range, to artesian wells and mound springs in the Lake Eyre region of South Australia. Water flows freely to the surface at mound springs because it is under pressure (having flowed down from the mountains of the Great Dividing Range).

Idealised cross-section through the Great Artesian Basin

Source: http://www.sea-us.org.au/roxstop97/msinfo1.htm


Photo above: Mound springs in the dessert regions of Australia are important ecological niches because they provide the only source of permanent water over much of the continent. There major concern that mining operations at Olympic Dam and other locations will (and have!) depleted the local aquifers to cause the drying-up of natural mound springs.

Above: location of mound springs in the GAB (http://www.sea-us.org.au/roxstop97/msinfo1.htm) Management (and replenishment) of groundwater

In Adelaide’s northern suburbs, stormwater runoff is diverted into man-made wetlands at various localities along the Salisbury Highway. These are the largest artificial wetlands in the southern hemisphere. Although the construction of wetlands may well be an environmentally useful method of dealing with society’s excess (slightly polluted) water and providing habitats for endangered flora and fauna, in reality there are limited sites available for the construction of wetlands. Our total excess (run-off) water far exceeds the amount that could be used in wetlands that are in reasonable proximity to our cities.

Amongst the many environmental problems that have emerged over the last few decades, decisions still need to be made regarding:

• what to do with increasingly large volumes of storm water from our “urban spread”?

• increased salinity of our aquifer systems due to excessive pumping of water for agricultural use. (Current consumption of underground water supplies appears to be unsustainable!)

• overall stress of the groundwater system due to overuse.


Aquifer Storage and Recovery (ASR) may be the partial solution to many of society’s urban water problems. ASR is increasingly used to store excess water. An ASR program in the Adelaide region treats surface runoff from roads and rooftops (stormwater) and waste water (even treated sewerage) and stores it in the local aquifer system. However, the economic feasibility and environmental sustainability of this project continues to be debated in the media and the scientific community.

Various feasibility studies appear to indicate that society could (and maybe should) store excess water underground. Groundwater in the Adelaide region is not being replenished at the same rate as it is being used. In particular water from Adelaide’s deep aquifers is being used for industry including the manufacturing of beer and soft-drinks. This water entered the aquifers tens or hundreds of thousands of years ago

during times of higher rainfall. Because we are presently living in a semi-arid period, the water in these aquifers is not being replenished.

Groundwater in localities such as Mount Gambier and many remote communities on the Eyre and York Peninsulas rely entirely on groundwater for all their domestic and commercial water needs. These areas are facing similar problems to those of the Adelaide region.

The principal behind ASR is that excess water collected at the surface (over winter) can be injected into an aquifer for storage, and then extracted during summer for use for crop irrigation or maintaining wetlands, as indicated in the adjacent diagram.

This diagram and further information about ASR in the Adelaide region can be found at:

http://www.uwi.com.au/rd/publisher/fileUpload/181/attach/Martin&Dillon%20AWA%202002%20Water.pdf#search=%22storage%20of%20groundwater%20in%20Adelaide%22

The following figures have been taken from:

http://www.dwlbc.sa.gov.au/water/groundwater/capabilities/asr.html#ASR_Development_in_the_Adelaide_Region

Please visit this site for a full explanation of ASR in the Adelaide region. In summary, presently there are 22 operation projects in the Adelaide region. Together these inject 2000 ML of urban and rural run-off water into the local aquifer system.

Below: Conventional groundwater/aquifer exploitation: Here fresh water is simply pumped out and saline water gradually recharges the aquifer.


http://www.uwi.com.au/rd/publisher/fileUpload/181/attach/Martin&Dillon AWA 2002 Water.pdf#search=%22storage%20of%20groundwater%20in%20Adelaide%22





Below: With ASR, the height of the water-table varies as indicated in the diagrams. With a well-managed ASR system, ideally saline water should not invade the aquifer near the well-bore.

CHANGES IN CO2 CONCENTRATION

The concentration of carbon dioxide (CO2) in Earth's atmosphere has risen steadily over the past 150 or so years, from about 280 parts per million (ppm) in 1850 to about 350 ppm in 2000. This increase is due largely to the combustion of fossil fuels. Since the Industrial Revolution, nearly 1.5 x 1011 tonnes of organic carbon have been mined and consumed in the form of coal, oil, and natural gas. Carbon dioxide is the largest single waste product of modern society. The average person on Earth is responsible for the release of almost four tonnes of CO2 each year, and the amount is even larger in the developed countries. In 1985 the total global emission of CO2 was only 5 x 109 tonnes of carbon. However, by 2003, total global emission was close to 7.3 × 109 tonnes, up 4.5% on the previous year!


Source: http://cdiac.ornl.gov/trends/emis/glo.htm

Approximately half of the carbon emitted since the Industrial Revolution persists in the atmosphere today. The balance is presumed to have made its way into the oceans or to have been incorporated into organic matter on land. Uptake of CO2 by the oceans is limited by the supply of carbonate ions in surface waters. The carbonate ion content of waters at the ocean surface is small, and sustained uptake of CO2 requires a continuous supply. It has been estimated that over a 100-year period, about 10% of the water in the oceans is exposed at the surface. The consequences of this fact are that only little of the CO2 that is released into the atmosphere can be absorbed by the oceans.

A continuing rise in carbon dioxide emissions is inevitable. If current estimates for the reserve of fossil fuels (about 4 × 1012 metric tons of carbon) are considered, and if it is assumed that half of this reserve will be used up over the next 100 years, the level of CO2 could exceed 1000 ppm by Topic 5.3 Sustainable Future of 70

2100. If one assumes more conservatively that the consumption of fossil fuels will double over the next 100 years, CO2 may be expected to grow to about 600 ppm, approximately twice its concentration in 1850. The above graph shows changes in the atmospheric concentration of CO2 since 1000 AD, as measured by two ice cores and the volcano observatory at Mauna Loa, Hawaii. It is evident that the level of CO2 in the atmosphere remained constant until the Industrial Revolution, after which it has been increasing at an ever-faster rate.

Analyses of ice cores has shown that, throughout at least the last 10 000 years, periods of high CO2 concentration have coincided with periods of higher global temperatures. This is understood to indicate that CO2 causes a ‘greenhouse effect’. During period when levels of CO2 were high, heat otherwise reflected from Earth is instead trapped and prevented from radiating into space. If left unchecked, the higher global temperatures that we have experienced in the past few decades will cause the Arctic and Antarctic ice sheets to melt, thereby increasing the global sea-level. Eventually coastal cities (e.g. Adelaide) will be flooded, and low-lying islands will be completely inundated. Ultimately, unless action is taken, all of Earth’s present-day ecosystems will be stressed and eventually destroyed.


EXERCISES 1. Explain the meaning of the term ‘Sustainable Future’.

MANAGEMENT OF RESOURCES 1. Describe the essential feature of renewable resources.

2. Explain why each of the following resources is considered to be renewable.

Soil:

The atmosphere:

Water:

Oceans:

3. Describe some of the processes that may lead to diminution of the above resources over time.

Soil:

The atmosphere:

Water:

Oceans:


4. Explain why some of our resources are said to be non-renewable.

5. List some examples of non-renewable resources.

6. How can we decrease the rate at which some of our resources are used?

7. The graph below shows known and predicted trends in Australian oil supply and demand from 1980 to 2005.

a. Describe the trends in existing developments, known discoveries

and new discoveries between 1995 and 2005.

b. What trend in demand is shown for the whole period shown on the graph?


c. Do you think synthetic fuels are likely to make a significant contribution to Australia’s energy needs in the foreseeable future?

d. How will Australia obtain most of her oil by the year 2005?

e. What is a big disadvantage of this requirement?

8. a. Discuss the advantages which renewable energy sources possess over fossil fuels.

b. What is the principal use of renewable energy sources?

c. What important use of fossil fuels is unlikely to be replaced by renewable energy sources in the foreseeable future?

9. For what purposed can solar technology be used?

10. Discuss some of the limitations of solar technology.


11. For what purposes are solar cells used today?

12. Discuss the use and limitations of wind power.

13. What are the requirements for geothermal energy to be a viable energy source?

14. Explain how energy stored in heated rocks may be used to generate electricity.

15. What limitations exist on the use of this energy?


EXPLORATION FOR GEOLOGICAL RESOURCES 1. Why is it most unlikely today that a valuable mineral deposit will be

indicated by the activities of a burrowing wombat?

2. Give one reason why exploration for mineral resources is inevitably a very expensive and risky undertaking.

3. Why is a knowledge of the structure of known ore bodies, such as the Broken Hill deposit, of considerable value to an exploration geologist?

4. Explain why a variety of geophysical methods may assist with the discovery of mineral deposits.

5. Why is it possible for magnetic surveying to lead to the discovery of deposits of non-ferrous metals, such as copper?

6. Explain why a small increase in the strength of the earth's gravity, called a gravitational anomaly is likely to occur in the region of rocks containing ores of metals.


7. The diagram below shows an airborne gravity and magnetic survey over an area containing a mineralised igneous intrusion surrounded by sedimentary rocks. Indicate the patterns of magnetic and gravitational field strength that will be detected by the survey.

8. Explain why chemical analysis of soils, stream sediments and water

samples may lead to discovery of a mineral deposit.

9. Describe the two stages in which a geochemical survey may be carried out.


10. The diagram below shows a system of streams where a geochemical survey has been conducted. The results obtained in different parts of the stream system are also shown on the diagram. Indicate on the diagram where a more detailed analysis to define the anomalous zone would take place.

11. The adjacent

excerpt from Australia's Little Cornwall, by Oswald Prior, as well as illustrating the obstinacy of Cornishmen, presents an excellent example of the association between mineral deposits, rock types and the surrounding vegetation.

With the obstinacy that was one of their marked characteristics, they refused to believe that the same rules did not apply to finding both stream tin and alluvial gold.

This obstinacy is illustrated by the story of a young Englishman who informed a party of Cousin Jacks that they had little hope of finding gold at the spot where they were digging.

“What the devil do ‘ee know ‘bout it?” one of the Cornishmen growled. The Englishman pointed to the yellow-box trees, Eucalyptus melliodora, that grew farther down the valley.

“Those trees are your guide. They grow only where there’s likely to be gold underneath. There’s none of them up here.”

The Cousin Jacks laughed at such an idea, and went on to do an immense amount of useless digging — their “duffer” holes can still be seen today — whereas many of the men who dug only where there are yellow-box trees — which grow only where there is quartz in the subsoil — had good returns.

a. Why would the same rules not necessarily apply to finding both

stream tin and alluvial gold?


b. Why was gold only found in areas where the Eucalyptus melliodora grew?

12. What type of information is provided by a seismic survey?

13. For what type of exploration programme is seismic surveying most useful?

14. In what type and ages of rocks would an exploration geologist look for petroleum deposits?

15. Explain why a search for metallic ores is unlikely to be undertaken in the same region as a search for petroleum deposits.

16. Explain how a seismic survey is carried out.


17. The adjacent diagram shows the equipment set up for a seismic survey.


a. Label the thumper

truck, the seismograph recording truck and a geophone.

b. Indicate the paths of

waves emitted by the thumper truck, reflected off boundaries between rock strata and received by the geophone.

18. At what stage in an exploration programme is drilling likely to be

undertaken?

19. Why do you think drilling is undertaken at this stage in the programme, rather than earlier?

20. What information is necessary before a drilling programme is undertaken?

21. List some of the information provided by a drilling programme.

ABORIGINAL HERITAGE ACT (1988) 1. What is the purpose of the Aboriginal Heritage Act of 1988?

2. According to the Act, who determines whether land or objects are of significance to Aboriginal heritage?

3. Is there any avenue of appeal against decisions made by these people?

4. To whom would an appeal be directed?

5. Who advises the Government on statewide aboriginal heritage interests?

6. What key functions under the act are delegated to traditional owners at their request?


EXTRACTION PROCESSES 1. What is the most important factor that must be considered when

selecting a method of mining a deposit?

2. What are the advantages of open-cut mining?

3. What types of climate make open-cut mining difficult?

4. What environmental problems are associated with open-cut mining?

5. Describe, with the aid of a

diagram, the type of deposits that are most suitable for open-cut mining.


6. a. Name one feature which significantly affects the profitability of an open-cut mine.

b. Explain, by completing the adjacent graph, why the profitability of the mine decreases very rapidly as the depth of the ore increases.

c. What decision may eventually have to be made?

7. Describe the functions of the benches in an open-cut mine.

8. The diagram below shows, in much simplified form, the essential features of an underground mine. On the diagram, label the following features:

ore body, shaft, drive, stope, headframe, winding house.


9. Briefly explain the function of each of the following features of an underground mine:

Shaft:

Drive:

Stope:

Headframe:

Winding house:

10. Draw a diagram showing a decline. 11. What is the advantage of a decline in a large mine?


IN SITU LEACHING 1. Summarise the essential features of the in situ Leaching technique.

2. For what types of deposit is the in Situ leaching technique suitable?

3. Describe two limitations on the location of a deposit for which ISL is suitable?

1. 2. 4. Name two metals that are typically extracted by ISL.

5. Describe the measures taken to ensure an economic uranium recovery rate and to prevent the escape of the highly corrosive and toxic solutions into the wider environment.


6. The diagram below shows the essential features of an ISL plant.

a. On the diagram, label the aquifer containing the orebody. b. Draw labels on the diagram to indicate the following directions of

solution flow: i. along the surface pipes. ii. into the production well iii. to and from the processing plant.

7. Describe the procedures carried out in the surface processing plant.


8. List seven advantages of this technique compared to open-cut and underground mining.

1.

2.

3.

4.

5.

6.

7.

EXTRACTION OF PETROLEUM 12. Explain the essential difference in layout and construction between

on-shore oil wells and off-shore oil wells.

13. The diagram below shows an oil rig above an extensive offshore oil and gas field. Complete the location to show where one or more recovery pipes may be constructed and where oil and gas may be trapped.


14. The diagram below shows one type of oil well. On the diagram, label oil, water, gas, oil flow to surface.


ENVIRONMENTAL IMPACTS 1. Discuss the environmental impact of the exploration phase of resource

extraction.

2. Explain why this impact may be more significant than it would at first appear.

3. List some features of the infrastructure required for a mine in a remote area that will inevitably have an impact on the environment.


4. The diagram below shows a typical open-cut mine or quarry, and some of the activities associated with its operation.

a. Indicate on the diagram the locations of sites and/or operations

which would be considered as forms of pollution, and detrimental to the environment. Write a number (1, 2, 3 etc ) by each of the detrimental features.

b. Discuss each of the features you numbered on the diagram.

c. What detrimental situation should never have been allowed to occur?

d. Add feature/s to the diagram which would decrease this problem. e. Suggest some ways by which the area may be rehabilitated once

the mine or quarry has been worked out.


5. The diagram below shows some of the surface operations associated with an underground mine and the associated smelter. Sulphide ores are being extracted and smelted.

a. Number the features of this operation which would be

detrimental to the environment. b. Discuss the features you have numbered on the diagram.

c. Which two of the above features are likely to have the worst effect on the environment?

b. Explain why this is so.


6. The photograph below shows a typical Adelaide hills' face stone quarry.

a. Suggest why benches are used in the quarry, rather than a

vertical face, which was the practice before 1956.

b. In what ways is use of these benches more detrimental to the environment than a vertical quarry face?

c. List the procedures that will probably be carried out to rehabilitate the area after the quarrying operations cease.


d. What factors probably led to the opening up of quarries, such as Stonyfell quarry, on the hills' face?

e. What has led to the moves to rehabilitate worked-out quarries and hide the scars?

f. What steps may be taken to ensure that no new quarrying operations scar the Adelaide hills' face zone?

g. In the long run, who pays for siting operations for minimal environmental impact, as well as for rehabilitation of sites?


7. On the scale of the map of Australia below, which of the squares A, B, C or D most nearly represents the area of land that has been degraded by mining operations?

8. The diagrams below show three possible access roads to a quarry.

Comment on the desirability of each of the three arrangements: a. from an environmental point of view.

b. from an operational viewpoint.


9. Diagrams P and Q below show two possible ways by which material, such as stone, can be extracted from a quarry face.

a. Which of the two arrangements is more environmentally

satisfactory? Give a reason for your answer.

b. In what way do you think this method of working would affect the cost of the material being extracted?

Nuclear Vs. Coal 1. Discuss the importance on a global scale of nuclear power for

generating electricity.

2. List some of the advantages of using nuclear power.


3. Explain why there is considerable opposition to the mining and export of nuclear fuel, and concern over use of nuclear reactors.

SOIL DEGRADATION 1. Name two major causes of soil degradation.

2. What is the geological cause of Australia’s salinity problems?

3. Describe, with the aid of

diagrams, the major cause of dry land salting.

4. Discuss the causes and effects of irrigation salting.


5. Discuss the extent of salinity problems in Australia.

6. Describe three effects of salinity in Australia.

7. Describe the management measures that can be taken to reduce salinity.

8. What structural measures can be taken to reduce salinity?

9. What major problems are associated with all these methods of reducing salinity?

10. Explain why the early settlers adopted inappropriate techniques for farming Australia’s soils

11. What is the most important requirement for prevention of soil erosion by water?


12. Describe measures that should be taken to ensure that water soaks into the soil.

13. Discuss two causes of wind erosion.

GROUNDWATER POLLUTION 1. List some of the human activities that result in pollution of

groundwater.

2. Name two results of groundwater pollution.

3. Complete the adjacent diagram to show a path of water pollution that could affect people working in the dairy.


4. Describe an example of groundwater pollution that is extremely dangerous to a large number of human lives.

5. The adjacent diagram shows a coastal area containing numerous groundwater bores.

Show on the diagram how the bores will affect the water table and allow the groundwater to become contaminated.

6. Explain why this type of pollution can result in long-term diminution

of water supplies to coastal communities.


MANGAGEMENT OF GROUNDWATER 1. Name the two considerations that must be addressed in a

groundwater management programme.

2. Describe the two factors that must be balanced when determining the quantity of groundwater to be extracted.

3. Explain why too much water can present a problem for wetlands.

4. Describe two reasons why it is very difficult to remove pollution from groundwater once it has occurred.

5. What strategies are needed to maintain groundwater quality?

6. Discuss the most important factor involved in management of contamination from a variety of sources.

7. What types of information are sought in a research programme to identify causes of groundwater pollution?

8. Explain how data on groundwater quantity and quality is obtained.


CHANGES IN CO2 CONCENTRATION 1. The graph below shows how the concentration of atmospheric carbon

dioxide in parts per million (ppm) has changed between the years 1000 and 2000.

a. Describe the changes shown on the graph.

b. In what year did the increase in carbon dioxide concentration begin?

c. What significant event in human history was just beginning at this time?

d. What does the shape of the graph suggest about future atmospheric carbon dioxide levels?


2. What factors have caused this change in the concentration of atmospheric carbon dioxide?

3. Describe two processes by which carbon dioxide is removed from the atmosphere.

1.

2. 4. What factors limit the amount of carbon dioxide absorbed in each of

these processes? 1.

2. 5. Describe the evidence that suggests that increased atmospheric

carbon dioxide is associated with higher global temperatures.

6. Explain how the increases in global temperatures will affect sea levels and hence human lives.


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