Flashcards in Unit 2: Earth's Resources Deck (49)
Natural Resources: Renewable
These resources can be replaced:
The gases in the air - O2 produced in photosynthesis, CO2 in respiration, N2 through the nitrogen cycle.
Water, recycled in the water cycle involving evaporation from the sea/, condensation as clouds in the atmosphere, cooling to release precipitation, surface run off back to the sea.
Living things, plants and animals are able to reproduce themselves.
Natural Resources: Non-Renewable
These resources are finite and cannot be replaced within a human lifetime (approx. 70 years):
Some natural resources are non-renewable or finite e.g. coal, oil, natural gas, soils, rocks and minerals, metallic ores, uranium etc.
Many of the resources around us are not renewable, they are man-made e.g. buildings, transport, machinery.
Physical resources are primarily inorganic materials, including rocks, minerals, water and aspects of the climate.
Biological resources refer to the living landscape and include the plants, animals, microorganisms and other aspects of nature.
Flow resources don't remain in one location and move about because of natural actions in the physical environment. Examples include: running water, radiation, wind and tides.
Stock resources are resources that can be permanently expended, and therefore non-renewable. Examples are coal and petroleum.
The Earth's Spheres
The atmosphere, The Hydrosphere, The Biosphere, The Geosphere
Examples of Geosphere
Atmosphere: Impact of weather and storms (e.g. hurricanes) on landscapes. Volcanic eruptions causing ash clouds and changing weather
Examples of Hydrosphere
Atmosphere: Exchange of water vapour between oceans and atmosphere (e.g. evaporation, condensation). Greenhouse effect (water vapour). Ocean currents. El Nino event - climate variability.
Geosphere: Weathering or the break down of rocks (e.g. freeze thaw) and erosion of rocks by water (coastal, river). Groundwater stores of water in underground rocks such as sandstone (aquifers). Tsunamis (undersea earthquakes).
Examples of Biosphere
Atmosphere: Photosynthesis in green plants. Respiration. Transpiration in plants.
Geosphere: Production of fossil fuels from organic remains (coal, oil, gas) over long periods of time. Geosphere provides mineral nutrients for plant growth.
Hydrosphere: Photosynthesis in green plants. Soil formation. Natural flood control (absorption of water by vegetation).
Earth Structure and Processes
Crust: outer shell of rock which ranges from 5km to 80km thick.
Outer Core: liquid layer of nickel and iron between 4000 and 6000C.
Mantle: makes up 80% of the earth's volume. It is a semi-molten layer of magma with temperature between 500 to 4000C.
Inner Core: solid ball of nickel and iron estimate to be around 6000C.
Plate Boundaries: exist where plates converge and are important areas for volcanoes, earthquakes and mineral development.
Tectonic Plates: crust is made up of over 25 slabs of rock.
The Earth's core is a heat engine which drives the process of plate tectonics. It has a temperature believed to exceed 6000C due to 3 main reasons:
1. Residual heat from when the planet formed and accreted (from collisions of material in space), which has not yet been lost.
2. Frictional heating, caused by denser core material sinking to the centre of the planet.
3. Heat from the decay of radioactive elements such as uranium and thorium. This is believed to produce about 50% of the Earth's inner heat.
Convergent Zones: where plates collide. Oceanic plates which are thinner, but denser are forced under the continental plates in a process known as subduction.
Divergent Zones: where plates separate, leaving a void where hot magma form underneath can be forced up creating volcanoes and rock formations. The Atlantic Ridge on which Iceland sits was formed in this way.
Conservative/ Transform Zones: where plates move past each other in opposite directions or at different speeds. The friction produced can create earthquakes.
Is thermal energy generated and stored in the Earth. It is a clean and renewable energy, with very low carbon emissions and in countries on plate boundaries it can make significant contributions to energy consumption (25% of Iceland's energy) where water pipes can run underground to heat water, generate steam which turns turbines and produces electricity. Alternatively the hot water can be used to heat homes and buildings directly. The Geothermal energy can create tourist attractions (e.g. Blue Lagoon in Iceland) which can raise money for the country. However, start up and installation costs can be high and it requires high water use, which can be contaminated with sulphur compounds.
There are three main rock categories:
1. Igneous rocks develop in the volcanic areas. Extrusive rocks form from lava which cools on the Earth's surface, producing small grained rocks such as basalt. Intrusive rocks cool form underground magma, creating rocks with larger crystals such as granite.
2. Sedimentary rocks are formed from grains of sediment (sand, mud) or organic material which has been laid down underwater (lake or sea beds and compressed over time. Examples include sandstone, chalk, limestone, coal and shale).
3. Metamorphic rocks have been changed by heat and pressure within the Earth's crust. Limestone can metamorphosis to form marble and shale to slate.
The three rock types can interchange over long periods of time within the rock cycle
Minerals and Ores
A mineral is a naturally occurring inorganic solid, with a definite chemical composition, and an ordered atomic arrangement. An ore is a naturally occurring solid material from which a metal or valuable mineral can be extracted profitably.
Destructive Plate Boundaries
Where plates meet (converge), denser material (usually oceanic plates) is forced underneath continental plates (known as subduction). Water and sediment can also be dragged down towards sources of heat, creating super-heated hydrothermal fluids, which can dissolve minerals. When these fluids are cooled mineral deposits (e.g. copper) can be created.
Constructive Plate Boundaries
At divergent plate boundaries, convection currents in the mantle force plates apart. Seawater seeping into cracks in the sea bed come into contact with igneous rocks. Superheated fluids travel upwards and contact with cold seawater results in the deposit of metallic elements such as iron and zinc, adjacent to features known as "black smokers".
Minerals Formed Within the Earth: 1. Deposits from Hydrothermal Fluids
(a) Porphyry copper (chalcopyrite ore)
At destructive plate boundaries; water can penetrate into cracks under the sea bed and be heated by hot magma to high temperatures to form hydrothermal fluids. Step 1: Water which has been separated from magma, Molten magma, Cooling magma forms granite. Step 2: Water is superheated and causes surrounding rocks to fracture, Minerals dissolved by hydrothermal fluids cool down in cracks forming minerals.
(b) Vein deposits
Similar to porphyry copper, as hot magma forces its way up through cracks and fissures underground, it can heat up groundwater which dissolves minerals from surrounding rocks near to the intrusion. These rising hydrothermal fluids can deposit ore minerals in these tiny fractions, including lead (galena ore) and tin (cassiterite).
(c) Sea-Floor Sulphide Deposits (form at constructive plate boundaries)
Seawater seeps into cracks and is heated by rising magma. These superheated fluids dissolve rocks. Black smoker deposits form at the surface. Sudden cooling of these fluids when they reach the ocean creates mineral deposits of copper and zinc (sphalerite) ore on the sea bed.
Minerals Formed Within the Earth: 2. Magmatic Segregation
As magma cools in magma chamber, heavier minerals e.g. chromite (ore of chromium can form). Step 1: As magma cools slowly, heavy minerals sink to the bottom of the magma chamber. Step 2: Layer of ore minerals.
Minerals Formed Within the Earth: 3. Contact Metasomatism
This refers to a process of chemical change in rocks adjacent to volcanic intrusions. This process helps produce ores of iron (haematite) and lead (galena). Step 1: Superheated acidic fluids react with neighbouring rocks e.g. alkali limestone, Granitic magma (acidic). Step 2: Mineral ores of iron and lead have replaced limestone, Solid granite forms.
Minerals Formed Within the Earth: 4. Pegmatite's
Pegmatite's are igneous rocks that form during the final stage of a magma's crystallisation. The magma which is left after granite has crystallized is often rich in pockets of superheated water, which cool very quickly to form very large crystals of ores such as uranium (uraninite) and lithium.
Minerals Formed of the Earth's Surface: Gold
Process: Placer deposits.
Description: Theses are deposits within alluvial (river washed materials). Within sedimentary processes, heavier metal elements, often in their pure form such as golds, sink to the bottom of features such as waterfall plunge pools and potholes (e.g. in rivers) and collect. Erosion and weathering of the rock above can expose the minerals.
Minerals Formed of the Earth's Surface: Aluminium (Bauxite)
Process: Residual deposits.
Description: In tropical climates, the chemical weathering of granite and sandstone bedrock produces laterite soils. The chemical weathering occurs due to acidic conditions from rainwater and humus content. Soluble rock particles are dissolved and washed out, leaving behind the insoluble compounds such as aluminium oxide (a major component of bauxite ore).
Minerals Formed of the Earth's Surface: Nickel (Limonite)
Process: Residual deposits
Description: Where coarse grained igneous rocks (peridotites) are weathered, deposits of nickel silicate develop between the soil and the bedrock.
Important Minerals: Aluminium
Qualities: Low density (so has a low weight). Strong, even at low temperatures. Anti-corrosive. Non-toxic. Good reflector of heat and light. Can be easily shaped and machined. Easy to recycle (requiring only 5% of the energy to make it).
Formation: Bauxite (the main aluminium ore) forms by the chemical weathering of acidic tropical soils. The insoluble mineral (bauxite) contains aluminium oxide which is left behind as a clay type compound.
Extraction/ Production: Bauxite is mined in Australia, Guinea, Brazil and other tropical areas by open-cast mining. The clay is washed off and the ore is crushed and refined with caustic soda and lime to produce alumina (purer aluminium oxide) which is then dried to a powder. Powder is dissolved in cryolite and heated to over 1000C and a current is passed through - process known as electrolysis. The molten metal is drained off.
Main Uses: World's second most widely used metal, used in;
- Vehicle, aircraft and train panels.
- Engines (blocks, cylinder heads and transmission units).
- construction (aluminium and wall cladding).
- Cabling (to reinforce steel).
Important Minerals: Baryte (main ore of barium)
Qualities: Very heavy element. Very low solubility. Non-toxic. Has ability to block x-ray and gamma-ray emissions.
Formation: Forms in carbonate rock (limestone) which have been heavily weathered. Large baryte deposits are found at the soil-bedrock contact. It can also be formed in hydrothermal veins (volcanic areas).
Extraction/ Production: Extracted by both surface and underground mining. Mined material is then processes using straightforward methods to produce correctly sized product and to remove waste materials.
Main Use: Weighting fluid in oil and gas drilling. Biomedical imaging - barium meals highlight clear parts of the digestive system during x-ray photography. High density filler for paper, rubber, plastics.
Important Minerals: Clay (purest forms are chins clays/ kaolin)
Qualities: Typically insoluble. Plasticity and flexibility. Shrinkage under firing and air drying. Easy to colour and glaze.
Formation: Formed by surface weathering of rocks such as the chemical decomposition of granite and the solution of limestone. Clays are the insoluble residues left behind.
Extraction/ Production: Most clay is mined by open-pit methods. Some kaolin is extracted by dredging and hydraulic processes (high pressure hoses).
Main Uses: Making bricks and roof tiles. Ceramics, porcelain. Paper making (kaolin used to make glossy paper). Fuller's Earth (remove colour in oils - bleaching agent). Fining agent in beer/ wine making (removes cloudiness). Cat litter.
Formation of Shale
Shale is a fine-grained sedimentary rock that forms from the compaction of silt and mud on sea and lake beds between 150 and 500 million years ago. where organic remains (plants, micro-organisms) died and decomposed pockets of oil and gas were trapped within the shale, which is porous.
Discovery of Shale
In the mid 19th century, the Scottish chemist James "Paraffin" Young devised a method of distilling paraffin from oil shale (torbanite). Production grew for the next century until petroleum became widely available after WW2. Discovered in the late 1700s, the tar sands in Alberta, Canada are the biggest energy project in the world. currently producing 1.9 million barrels of oil a day.
Extraction of Shale
With conventional oil reserves becoming harder and more expensive to access, geologists are returning to shale as a means of providing oil and gas. Modern extraction techniques include hydraulic fracturing (or fracking) where water, chemicals and sand are pumped at high pressure into underground shale deposits to allow gas to flow into wells where it can be pumped to the surface.
Advantages of Fracking
Allows access to more reserves of natural gas and oil. Keeps fuel prices low which benefits the overall economy. Using natural gas from fracking to generate electricity instead of coal is cleaner and reduces CO2 emissions. The movement from coal to natural gas in the USA has significantly reduced nitrogen and sulphur oxide emissions (which cause acid rain). Decreased dependency on foreign oil particularly the "volatile" Middle East area. Creates highly skilled engineering jobs in extraction and processing. Government revenue (and GDP) increased via taxation of oil companies.