A LEVEL ENVIRONMENTAL SCIENCE: The Lithosphere
Terms in this set (56)
made up of the solid crust and the upper mantle where rocks are rigid, cold, and brittle. divided into tectonic plates.
resources provided by the lithosphere
mined metal ores, non-metal minerals, fossil fuels, biogeochemical cycles (carbon, nitrogen, phosphorous), growth medium (soil).
mineral resources extracted from the lithosphere
- iron = buildings
- aluminium = packaging foil
- tin = solder, rust prevention
- uranium= nuclear fuel for power stations
- form when lava/magma cools
- make up 95% of earth's crust
- sediment accumulates overtime. sediment is squeezed and becomes rock e.g. limestone.
- fossils are found in sedimentary rocks.
- has been changed by heat and pressure.
- found deep in the earth where it is hot or near tectonic plates.
- e.g. limestone turns to marble.
hydrothermal ore deposits
- important and varied group of ore deposits that form in many of the world's richest ore deposits.
- formed from hot aqueous fluids containing metals in solution.
- sources of heat, water, and metals are required for formation.
forms of weathering in sedimentary rocks
- physical = physical action e.g. freeze-thaw.
- biological = animals burrowing/tree roots break rock.
- chemical = rocks chemically attacked e.g. carbonation.
formation of sedimentary rocks
- layers of sediment are deposited at the bottom of seas or lakes.
- over millions of years, layers get squashed by the layers above.
- salts that are present in the layers start to crystallise as water is squeezed out. salts help to cement particles together.
features of sedimentary rocks
- layers or bands across them.
- often contain fossils.
- scrape and crumble easily.
formed by the sedimentary processes of weathering, erosion, transport, and deposition. e.g. diamond and gold.
requirements of placer deposit formation
- pre-existing mineral veins exposed at the earth's surface.
- dense, physically and chemically resistant ore minerals.
- erosion and transport processes.
- suitable sites of deposition where ore minerals will be concentrated.
formation of placer deposits
mineral veins exposed at earth's surface will be weathered. during weathering, ore will be broken up mechanical weathering or left as insoluble material. ore will be sorted into individual grains.
properties of placer deposits
- hard. survive abrasion and attrition during transport.
- chemically unreactive - not dissolved and taken into solution.
- dense - deposited first when current velocity decreases.
locations of placer deposits
- inside meander bends.
- plunge pools.
- upstream of projections.
- downstream of confluences.
- on beaches.
form in shallow marine environments.
- amount of resource that can be economically exploited now for use later using current technology.
- source is finite but quantity may change in the future.
- amount of resource that could potentially be exploited using futuristic technology.
- we are currently unaware of how it may change current resource quantity.
surface/open cast mining. used for coal.
precious metals. e.g. gold. forms sink holes.
material running in horizontal bands. can be exploited from the side of a hill.
often for stone and building materials.
factors affecting mining viability
- ore purity
- economic demand
- chemical form
- overburden and hydrology
- transport costs
heavy metal pollution
a metal with high atomic mass will interfere with physiological or neurological processes and may eventually cause death.
they are not broken down, so become permanent additions to the environment.
examples of heavy metals
acid mine drainage
the outflow of acidic water from metal mines or coal mines.
effect of acid mine drainage
when metal ions are in a dissolved form, they are more easily absorbed and accumulated by plant and animal life and so become more toxic.
increasing accumulation of a non-biodegradable substance (e.g. heavy metals) going up through the food chain. e.g. polar bears consuming multiple larger fish that have all consumed fish before them all containing heavy metals.
the gradual increase of the non-biodegradable substance (e.g. heavy metals) by consuming small amounts over a long period of time e.g. whales consuming millions of small fish that have each consumed small amounts of heavy metals
environmental consequences of mining
- noise and air pollution
- creation of soil heaps
- in situ leaching using cyanide
- pollution of surface and ground water (leads to acid rain).
acid mine drainage: neutralisation (liming)
- alkalinity of lime used to try and neutralise heavy metals.
- leaves behind toxic sludge that must be disposed of.
- cheapest option.
- often used as a first stage solution.
acid mine drainage: desalination
- neutralisation leaves behind high concentrations of sulphides (water extremely saline).
- should only have 200 milligrams of sulphides per litre of water.
- acid mine drainage has caused levels to rise to 2500 milligrams of sulphides per litre of water.
treatment of acid mine drainage
- can be active or passive.
- active is the use of liming to neutralise the acidic water.
- passive is the use of plants to filter out precipitates.
advantages to active acid mine drainage
- simple process which needs reduced labour and limited chemical input.
- buildings take up little space.
- processes large volumes of mine water continuously.
disadvantages to active acid mine drainage
- water from mines needs to be pumped into the treatment plant - often tens of miles.
- high building costs.
active treatment of acid mine drainage
- mine water enters tank and added sludge begins initial process of settling solids.
- lime added to raise pH and cause precipitation of metal hydroxides.
- flocculant added to coagulate metal solid and sludge settles out in the clarifier tank.
- process repeated.
process of passive treatment of acid mine drainage
- utilises natural biological processes and is sustainable.
- treats areas of natural wetland which trap and precipitate the metals.
- schemes involve construction of shallow, lined lagoons or cells.
- two main styles of treatment; aerobic cells and anaerobic cells.
passive treatment; aerobic cells
- lime added to incoming water to raise pH so that metals such as iron will precipitate out of solution.
- cells are lined and reeds, such as juncus, are planted.
- reeds are planted to absorb metals within their roots and to trap precipitating metals.
- reeds provide attachment sites for micro-organisms which will break down the metal compounds.
- process is very slow.
passive treatment; anaerobic cells
- aim to reduce the iron and filter the water through limestone.
- clay liner and soil prevent oxygen from entering.
- limestone filters mine water and raises the pH.
a toxic metal that is normally immobile in rocks, may become oxidised in a soil heap and become soluble.
drainage water can then carry this into nearby rivers.
passing mine drainage water through a bed of limestone can immobilise the metal and prevent it flowing into the river.
- spoil heaps are loosely compacted and unstable, causing landslides.
- drainage of rainwater by pipes in the base of the spoil heap prevents it form becoming water logged.
- caused by poor soil compaction.
- it can be prevented by the compaction of spoil and by leaving support pillars in deep mines.
any technique used to locate mineral deposits without actually coming into physical contact with them - usually involves analysing aerial photographs, satellite images, or thermal images.
measure variations in strength of the earth's gravitational field and density of rocks.
passing sound waves into the rock strata and then detecting, recording, and measuring the reflected signals via receivers.
using machines allows mining underground where it may be too hot or dangerous for people.
e.g. deep gold and platinum mines in south Africa - 3.8 km deep.
larger machinery in open-cast mines allows overburden and minerals to be extracted more quickly and cost effectively. mines up to 1000m deep have been developed to access more valuable minerals.
- bacteria oxidise sulphide ores and produce sulphuric acid which dissolves the metals.
- fungi produce acids that dissolve metals such as nickel, lead, copper, and tin.
- metals produced can be separated by electrolysis or by using carbon filters.
- some plants absorb metal ions from soil or water and concentrate them in their leaves.
- can be used to decontaminate polluted sites and as a method of metal extraction.
- once absorbed, the vegetation is harvested and incinerated.
- concentrated metals in the ash can be dissolved using acids, then separated by electrolysis.
- iron is a more reactive metal than copper and will displace copper ions from solution as solid iron which can be collected.
recycling metals; refrigerators
- 95% of a fridge can be recycled.
- older fridges release CFCs, so liquid nitrogen is used to capture the CFCs.
- 65-70% of a fridge is made of steel.
- 12% is plastic.
- the rest is CFCs or other materials.
recycling metals; aluminium
- difficult to separate and recycle.
- making aluminium is very energy intensive to make (made from bauxite).
- mostly contain iron.
- have small amounts of other metals or elements to give the required propertied.
- magnetic and give little resistance to erosion,
- e.g. vehicle scrap metal.
- do not contain iron.
- not magnetic.
- more resistant to corrosion.
- NPK fertilisers added for growth (nutrient loading).
- seeds given excess nutrients to ensure growth.
land reclamation; legumes
- legumes can rehabilitate land e.g. tarsands or metal mines.
- e.g. chickpeas, lentils, peanuts.
- legumes can generate their own nitrates by converting atmospheric nitrogen for uptake.
- important in nutrient poor sites.