HIGHER ENVIRONMENTAL

SCIENCE

Unit 2: Earth’s Resources

Revision Notes

NATURAL RESOURCES

Definition: Any property of the physical environment which humans can use tosatisfy their needs

The Earth’s natural resources include: land, air, water (seawater/freshwater), livingorganisms including plants and animals, coal, oil, natural gas (fossil fuels), metalores, minerals such as salt, baryte, quarried rocks e.g. sandstone, limestone,marble.

Renewable

These resources can be replaced:

•The gases in the air - O2 produced inphotosynthesis, CO2 in respiration, N2through the nitrogen cycle.

•Water, recycled in the water cycleinvolving evaporation from the sea/,condensation as clouds in theatmosphere, cooling to releaseprecipitation, surface run off back tothe sea.

•Living things, plants and animals areable to reproduce themselves

Non-Renewable

These resources are finite and cannotbe 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 arenot renewable, they are man-madee.g. buildings, transport, machinery

Natural Resources fall into 2 main categories

Resource Definitions:

• 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 do not remain in one location and move about because of naturalactions in the physical environment. Examples include: running water, solarradiation, wind, and tides.

• Stock resources are resources that can be permanently expended, and aretherefore non-renewable. Examples are coal and petroleum

2

THE EARTH’S SPHERES 3

The Earth system can be considered as four connected parts which continuouslyinteract with each other

The Atmosphere(air)

The Biosphere(all living things)

The Geosphere(Earth's interior, rocks)

The Hydrosphere(All Earth’s water)

Examples of these interactions include:

Atmosphere Geosphere HydrosphereGeosphere • Impact of weather and

storms (e.g. hurricanes) on landscapes

• Volcanic eruptions causing ash clouds and changing weather

Hydrosphere • Exchange of water vapour between oceans and atmosphere (e.g. evaporation, condensation)

• Greenhouse effect (water vapour)

• Ocean currents• El Nino event - climatic variability

• 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 sand-stone (aquifers)

• Tsunamis (undersea earthquakes)

Biosphere • Photosynthesis in green plants

• Respiration• Transpiration in plants

• Production of fossil fuels from organic remains (coal, oil, gas) over long periods

• Geosphere provides mineral nutrients for plant growth

• Photosynthesis in green plants

• Soil formation• Natural flood control (absorption of water by vegetation)

GEOSPHERE: EARTH STRUCTURE & PROCESSES

The Earth has a distinctive layered structure:

The Earth’s core is the heat engine which drives the process of plate tectonics. It has atemperature believed to exceed 6,000°C, due to 3 main reasons:

1. Residual heat from when the planet formed and accreted (from collisions of materialin 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.

Plate Tectonics

Plate tectonics is a theory that the plates move slowly over the semi-molten mantle, dueto heat convected from the Earth’s core. The plates can interact in a number of ways:

• Convergent zones are where plates collide. Oceanic plates which are thinner, butdenser are forced under continental plates in a process known as subduction. Thiscan produce fold mountains (e.g. Rockies, Andes) and explosive volcanoes

• Divergent zones are where plates separate, leaving a void where hot magma fromunderneath can be forces upwards creating volcanoes and rock formations. The MidAtlantic Ridge on which Iceland sits was formed in this way.

• Conservative or transform zones are where plates move past each other in oppositedirections or at different speeds. The friction produced can create earthquakes.

Geothermal Energy

Geothermal energy is thermal energy generated and stored in the Earth. It is a cleanand renewable energy, with very low carbon emissions and in countries on plateboundaries it can make significant contributions to energy consumption (25% of Iceland’senergy) where water pipes can be run underground to heat water, generate steam whichturns turbines and produces electricity. Alternatively the hot water can be used to heathomes and buildings directly. However start up and installation costs can be high and itrequires high water use, which can be contaminated with sulphur compounds.

There are three main rock categories:

1. Igneous rocks develop in volcanic areas. Extrusive rocks form from lava whichcools on the Earth’s surface, producing small grained rocks such as basalt.Intrusive rocks cool from underground magma, creating rocks with larger crystalssuch as granite.

2. Sedimentary rocks are formed from grains of sediment (sand, mud) or organicmaterial which has been laid down underwater (lake or sea beds) and compressedover time. Examples include sandstone, chalk, limestone, coal and shale.

3. Metamorphic rocks have been changed by heat and pressure within the Earth’scrust. 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

5

MINERALS AND ORES

A mineral is a naturally occurring inorganic solid, with a definite chemicalcomposition, and an ordered atomic arrangement. An ore is a naturally occurringsolid material from which a metal or valuable mineral can be extracted profitably

Plate tectonics and the associated activities of heat and pressure plays an importantrole in the development of ores. Many of the world's major deposits of minerals arefound near to current or ancient plate boundaries

Destructive Plate BoundariesWhere plates meet (converge), denser material(usually oceanic plates) is forced underneathcontinental plates (known as subduction). Waterand sediment can also be dragged down towardssources of heat, creating super-heatedhydrothermal fluids, which can dissolve minerals.When these fluids are cooled mineral deposits (e.g.copper) can be created.

Constructive Plate BoundariesAt divergent plate boundaries, convection currentsin the mantle force plates apart. Seawater seepinginto cracks in the sea bed come into contact withinto igneous rocks. Superheated fluids travelupwards and contact with cold seawater results inthe deposit of metallic elements such as iron andzinc, adjacent to features known as “blacksmokers”.

GEOSPHERE: ROCKS

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 bedand be heated by hot magma to high temperatures to form hydrothermal fluids.

(b) Vein depositsSimilar to porphyry copper, as hot magma forces its way up through cracks andfissures underground, it can heat up groundwater which dissolves minerals fromsurrounding rocks near to the intrusion. These rising hydrothermal fluids can depositore minerals in these tiny fractions, including lead (galena ore) and tin (cassiterite)

(c) Sea-Floor Sulphide Deposits form at constructive plate boundaries.

2. Magmatic Segregation

As magma cools in a magma chamber, heavier minerals e.g. chromite (ore ofchromium) can form

molten magma

water which has separated from magma

cooling magma forms granite

water is superheated and causes surrounding rocks to fractures

minerals dissolved by hydrothermal fluids cool down in cracks forming minerals

Seawater seeps intocracks and is heatedby rising magma.These superheatedfluids dissolve rocks

Sudden cooling ofthese fluids whenthey reach the oceancreates mineraldeposits of copperand zinc (sphalerite)ore on the sea bed.

black smoker deposits

As magma cools slowly, heavy minerals

sink to the bottom of the magma chamber

Layer ofore minerals

3. Contact Metasomatism

Refers to a process of chemical change in rocks adjacent to volcanic intrusions. Thisprocess helps produces ores of iron (haematite) and lead (galena).

granitic magma (acidic)

superheated acidic fluids react with neighbouring rocks e.g. limestone

solid granite

mineral ores of iron and lead have replaced limestone

4. Pegmatites

Pegmatites are igneous rocks that form during the final stage of a magma’scrystallisation. The magma which is left after granite has crystallized is often rich inpockets of superheated water, which cool very quickly to from very large crystals ofores such as uranium (uraninite) and lithium.

MINERALS FORMED ON THE EARTH’S SURFACE

Metal Ore Process DescriptionGold Placer

DepositsThese are deposits within alluvial (river washed materials)Within sedimentary processes, heavier metal elements,often in their pure form such as gold, sink to the bottom offeatures such as waterfall plunge pools and potholes (e.g.in rivers) and collect. Erosion and weathering of the rockabove can expose the minerals

Aluminium (bauxite)

Residual Deposits

In tropical climates, the chemical weathering of graniteand sandstone bedrock produces laterite soils. Thechemical weathering occurs due to acidic conditions fromrainwater and humus content. Soluble rock particles aredissolved and washed out, leaving behind the insolublecompounds such as aluminium oxide (a major componentof bauxite ore)

Nickel(limonite)

Residual Deposits

Where coarse grained igneous rocks (peridotites) areweathered, deposits of nickel silicate develop betweenthe soil and the bedrock.

Advantages of Fracking Disadvantages 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

• Does not reduce a nation’s dependence on fossil fuels and hinders investment inalternative renewable technologies

• Process still contributes to CO2 emissions• Methane leaks from fracking wells areargued to effectively reduce any net gain from emissions (switching from coal to gas)

• Chemicals used could contaminate groundwater (drinking) supplies

• Uses large quantities of water creating conflict with other users in arid areas (e.g. central USA)

• Drilling process can trigger small earthquakes

• Localised noise pollution from drilling rigs• Lack of research into impact of fracking (relatively new branch of environmentalscience)

The Fracking Debate

Through the use of hydraulic fracturing, the United States has become the world'slargest oil and gas producer and plans have been put in place to trial these systemsin the UK. However this process is considered very controversial:

GEOSPHERE: SHALE

Formation: Shale is a fine-grained sedimentary rock that forms from the compaction ofsilt and mud on sea and lake beds between 500 and 150 million years ago.Where organic remains (plants, micro-organisms) died and where trappedin the shale, pockets of oil and gas can remain within the shale.

Discovery: In the mid nineteenth century, the Scottish chemist James “Paraffin” Youngdevised a method of distilling paraffin from oil shale (torbanite). Productiongrew for the next century until petroleum became widely available afterWW2.

Discovered in the late 1700s, the tar sands in Alberta, Canada are thebiggest energy project in the world, currently producing 1.9 million barrelsof oil a day.

Extraction: With conventional oil reserves becoming harder and more expensive toaccess, geologists are returning to shale as a means of providing oil andgas. Modern extraction techniques include hydraulic fracturing (orfracking) where water, chemicals and sand are pumped at high pressureinto underground shale deposits to allow gas to flow into wells where it canbe pumped to the surface.

8

GEOSPHERE: IMPORTANT MINERALSMineral Qualities Formation Extraction / Production Main UsesAluminium • Low density (so has a

low weight)• Strong 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)

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

• 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 cryoliteand heated to over 1,000°C and a current is passed through -process known as electrolysis

• The molten metal is drained off

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

• Packaging - foil, cans• Cabling (to reinforce steel)

Baryte(main ore ofbarium )

• Very heavy element• Very low solubility• Non-toxic• Has ability to block x-

ray and gamma-ray emissions

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)

Extracted by both surface and underground mining,. Mined material is then processed using straightforward methods to produce correctly sized product and to remove waste materials

• 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

Clay(purest forms are china clays /kaolin)

• Typically insoluble• Plasticity and

flexibility• Shrinkage under

firing (baking) and air drying

• Easy to colour and glaze

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

• Most clay is mined by open-pit methods

• Some kaolin is extracted by dredging and hydraulic processes (high pressure hoses)

• 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

GEODIVERSITY

Geodiversity is the variety of rocks, minerals, fossils, landforms, sediments and soils,together with the natural processes which form and alter them. Geodiversity is importantto humans for a number of social, economic and environmental reasons:

• It is crucial to the delivery of ecosystem services (e.g. soil formation, filtering andstorage of water) upon which the existence of all living things depend

• Provides us with raw materials (fossil fuels, metals, building and constructionresources)

• Provides us with landscapes for aesthetic pleasure and recreation• A unique teaching and scientific resource, helping us understand issues such as

climate change, and sea level rise and the Earth’s pas (e.g. fossil studies)

In Scotland, there are a number of method used to conserve the nation’s geodiversity:

The overall responsibility for Scotland’s geodiversity rests with Scottish NaturalHeritage (SNH), the arm of government which deals with landscape conservation. Theywill work in partnership with other organisations including charities and environmentalgroups to conserve Scotland’s rich and varied geological heritage.

Geoparks are areassupported by UNESCO toimprove knowledge andawareness of these speciallandscapes and to promotesustainable development.Scotland has 3 Geoparks:the North West Highlands,Lochaber and Shetland

National Parks. Scotlandhas two: Loch Lomondand the Cairngorms,where there are severerestrictions on the use ofthe landscapes ofoutstanding scenery. Theyare managed by NationalPark Authorities

Local GeodiversityAction Plans (LGAPs).Promote awareness ofthese landscapes atlocal level involvingcharities and localcouncils.

Sites of Special ScientificInterest (SSSI). Thesedesignations give additionalprotection to uniquegeological or scenic areas

Scottish Fossil Codeaims to provides adviceon best practice in thecollection, identification,conservation andstorage of Scottishfossil specimens

Conserving Geodiversity

10

BIOSPHERE: SOILS 11

Soil is considered to be the primary resource as it supports all other life forms. It iscomposed of weathered rock particles, water and organic material from decaying plantsand matter (known as humus).

Soils take hundreds, even thousands of years to form and are considered to be non-renewable resources. A number of factors influence their formation:

The science of soil study is known is pedology. A few factors are particularly important:

• Temperatures will affect the rate of weathering, the rate of decomposition and the amountof organic material e.g. worms in the soil

• In areas of high rainfall, nutrients are leached or washed out through the soil. In dry areasthe nutrients are brought to the surface by a process known as capillary action

• The underlying geology will influence the time taken for the soil to form (due to rockhardness) and the pH of the soil. Rocks such as sandstone and granite tend to fromacidic soils, whilst basalt and limestone form alkali soils

• On steep slopes soils tend to be thin, but on gentle or flatter areas they are deeper.

Abiotic factors which affect soil (pH, moisture, porosity) are known as edaphic factors

Soil Structure

Soils tend to form a profile and some soils can have distinctive horizons or layers;

Soil Formation

AltitudeTemperature

Slope Angle

Rate ofErosionWater

ParentMaterial

Vegetation

Impact ofPeople

BioticMaterial

Time

Weathering

MineralComposition

Abiotic(non-living)

Factors

Biotic(Living)Factors

A0

A

B

C

AO horizon contains the most organic material (e.g. decomposing leaves, vegetation

A horizon is the topsoil (organic matter mixed with mineral matter)

C horizon contains the bedrock and weathered bedrock fragments (known regolith)

B horizon is the subsoil, where minerals gather which have been washed down (leached) from the

layers above

12BIOSPHERE: SOIL TYPES

BROWN FOREST SOILS

• Occur in areas of deciduous woodland, inlowland areas

• Decaying leaves produce a rich and deeplevel of humus each autumn

• Trees have deep roots and penetrate deepinto he soil to obtain nutrients and providinggood drainage

• Soil is well drained and aerated• Organisms like earthworms, mix the

materials together, so there are nodistinctive horizons

• Soils are leached, but not heavily, so thealuminium and iron oxides are mixedthrough the soil to give an overall browncolour

PODZOLS

• Occur in found on well drained uplandslopes, main vegetation is coniferousforest

• Pine needles help to create acidic humus• Podzols have distinct layers or horizons• Organisms do not like the acidic conditions

so there is little mixing between horizons• Soils are heavily leached, especially when

snow melts in winter and this creates aniron pan where iron oxides are built up.This can impede drainage

• Above the iron pan the leaching ofnutrients mans the soil is grey in colour

• Below the iron pan, some nutrients do getthrough which means the B horizon can beorange/brown colour (with iron compoundspresent)

Brown earths are fertile and suitable for agriculture, due to their good draining,suitable relief and high organic content. They can support a wide range of cropsfrom cereals (wheat, barley) and vegetables

Podzols are typically infertile with low productivity. They are principally used forsheep grazing, forestry and heather grouse moors. Where they are used for crops,draining is required along with fertilising and adding lime (to reduce acidity)

13BIOSPHERE: BARLEY & SEAWEEDBarley is the main cereal crop grown in Scotland. It has a relatively short growing seasonand grows well in the damp climate and slightly acidic soils which are widespread acrossthe country (although in some places lime needs to be added where soils are too acidic.The main uses include:

Animal Feed Half of the UK’s barley crop (almost all winter barley) is used to feedlivestock

WhiskyDistilling & Brewing

Malt whisky is a distilled alcoholic beverage made from water, barley andyeast. It hoes through a number of stages:

• Malting. Barley husks are steeped in water to release sugars, then dried• Fermenting. Malted husks are milled into a fine grain, mixed with water ina max at between 60 and 90°C and yeast is added to ferment the liquid (3-4 days). Nitrogen based yeast compounds perform a key role.

• Distilling. The liquid “wash” is heated to 80°C in a copper still and thealcohol vapour evaporates and an be condensed.

• Maturation. The alcohol is stored in used barrels for 12-21 years whichprovide additional colour and flavour to the whisky

Beer making actually follows a similar process, but a process of lauteringwhere the mash is separated into the clear liquid wort and the residual grainand hops are added for additional flavour.

Food processing

Used in the production of flour, malt vinegar, breakfast cereals, syrups, babyfoods and confectionery

Uses of SeaweedFertiliser Fertilisers are rich in potassium, nitrogen and magnesium have been used

by coastal communities for centuries in western Scotland and Ireland.Commercially produced seaweed fertilisers are becoming widely available.

Food processing

Molecules extracted from seaweeds known as hydrocolloids are used infood processing. These include:

• Alginates (formed from crushing and drying brown seaweeds) are jelly-likecarbohydrates used for their water holding, gelling, emulsifying andstabilising properties. Used as an additive in dairy and ice-cream products.

• Carrageenans (extracted from red seaweeds by cooking in hot alkali) areused to stabilise foods such as ice cream and chocolate milk. Also usedas a setting agent

Medicines • Agars (from red seaweeds) are used as a solid substrate for the growth ofbacteria and fungi and perform a vital role in microbiology.

• Seaweeds are also a source of iodine (used in sterilizing and treatinginflammations)

Cosmetics Carageenans are thickening agents used in toothpaste, skin care products,shaving creams, shampoos and hair conditioners

Fuel Although seaweed has been dried and burned for centuries, large scalefuels from seaweeds (“marifuels”) are at developmental stages

14BIOFUELSA biofuel is a fuel that is produced through contemporary biological processes, such asagriculture and anaerobic digestion, rather than a fuel produced by geological processessuch as those involved in the formation of fossil fuels e.g. coal and petroleum

Biofuels can be split into two main groups and the pros and cons of each can beconsidered:

Biofuel Type Feedstock & Processes

Advantages Disadvantages

1. First Generation Biofuels (made from conventional processes)Bioethanol Produced by the

fermentation of sugar, from a wide range of crops with a sugar or starch content e.g. sugar cane, corn, maize, wheat and sorghum

• Can use any plant for production, it only has to contain sugar and starch

• Burns cleanly with reduced exhaust gases

• Valuable farmland used for growing crops, leads to an increase in global food prices

• Deforestation of habitats (rainforests) to bring land into ethanol production

• Hygroscopic - it absorbs water from the air and ishighly corrosive

• Difficult to start vehicles in cold weather

Biodiesel Transesterification, which involves the separation of methyl esters (the fuel) and glycerine (useful by-product)

• Burns cleaner than conventional diesel

• Less particulatesreleased into air

• Glycerine used in pharmaceuticals

• More corrosive than standard diesel

• Vehicles need heating systems to start in cold weather increases engine conversion cost)

2. Second Generation Biofuels (advanced biofuels, that can be manufactured from various types of biomass, often using experimental technology)Biomethanol Pyrolysis

(distillation of wood)• Can be derived from non-food biomass (grasses, leaves, wood chips, husks)

• Can be derived from waste products

• Needs less farmland to produce

• Produces less energy by volume compared to petroleum based fuels

• Health risk - causes burning in contact with skin

Bio-crude oil Uses a thermo-chemical reaction, where organic material is rapidly heated to help decomposition into usable parts

• Made from algae (easy to cultivate)

• No net gain of CO2 is released into the air.

• Potential yields are substantially higher per hectare

• Technology is small scale and not fully developed at present

• Process is currently expensive to produce large quantities

This is the distribution and movement of water between the earth and the atmosphere

• 97% is stored in the oceans• 2% is found in ice caps e.g. Antarctica• 1% is found in lakes, rivers and groundwater

15THE GLOBAL HYDROLOGICAL CYCLE

Heat energy from the sun causes evaporation from water surfaces (oceans, lakes,rivers) and transpiration from plants. The warm, moist air (containing water vapour)rises, cools and condenses forming clouds. Winds blow the clouds over the land whereprecipitation occurs. Rain flows over the ground (surface run off) into rivers and backto the ocean, or downwards through the soil and rocks (groundwater).

INPUTS FLOWS STORAGE OUTPUTS

Precipitation (rain, hail, sleet and snow)

• Overland flow (surface run off)

• Throughflow (through the soil by infiltration and percolation

• Groundwater flow (through bedrock)

• Interception by vegetation

• Soil moisture storage

• Rivers and lakes (surface storage)

• Groundwater storage (aquifers)

• Discharge from rivers into sea / lakes

• Evapo-transpiration from water surfaces and plant leaves

• Sublimination (ice to gas directly) Extracted by humans

The drainage basin is a system with inputs, outputs, storage and flows.

Sublimination (from solid ice to gas withoutmelting)

16FLOOD HYDROGRAPHS

0 12 24 36 48 60 72

Hours from start of rain storm

3

2

1Dis

char

ge (m

3 /s)

Base flow

Through flow

Overland flowR

isin

g lim

b

Falling limb

Basin lag time

mm4

3

2

Peak flow

A hydrograph shows the relationship between rainfall and river flow (discharge).

Analysis of Hydrographs

• The baseflow of the river represents the normal day to day discharge of the river and isthe consequence of groundwater seeping into the river channel.

• The rising limb of the hydrograph represents the rapid increase in resulting from rainfallcausing surface runoff and then later throughflow.

• Peak discharge occurs when the river reaches its highest level. The time differencebetween the peak of the rain event and the peak discharge is known as the lag time orbasin lag.

• The falling limb (or recession limb as it is sometimes known) is when dischargedecreases and the river’s level falls. It has a gentler gradient than the rising limb as mostoverland flow has now been discharged and it is mainly throughflow which is making upthe river water.

• Normally after a heavy period of rain there is a time lag (the basin lag) beforefloodwater makes it way into the river channel. The basin lag will normally take longerif the region is highly vegetated i.e. the water takes longer to flow across the ground andmore is likely to be intercepted by plants or trees and some will be caught up in leaf litteron the woodland floor.

• In areas where there is little vegetation (including open farmland, areas of bare rock suchas steep mountains and built up urban areas with lots of tarmac, concrete and artificialdrains) the basin lag will be shorter and flooding is more likely. Deforestation will alsoreduce the basin lag and increase the risk of flooding

FACTOR

Shorter lag time - higher peakdischarge and steeper rising /falling limbs

Longer lag time - lower peakdischarge and more gentlerising / falling limbs

Basin size

Basin shape

Drainage Basin Density

Relief Steep slopes - speed up run off Gentle slopesType of precipitation

Intense rainfall / thunderstormsRapid snow melt

Prolonged rainfallSlow snow melt

Vegetation Few trees. Dense. Deciduous forest insummer. Coniferous forest(interception all year round)

Land Use DeforestationFarmland

ReforestationNatural Vegetation

Geology Impermeable (e.g. granite) Permeable (chalk, limestone)

Soils Clays (acts like impermeablerock)

Sands (allow percolation tosoils and groundwater)

Urbanisation High density (paved surfaces,tarmac with drainage systems)

Low density (parks, gardenswith abundance of vegetation)

Human Activities Farmland areas have greaterrun off than wooded areas,particularly where it is drained

Dams (flood control) reducedischarge. Reservoirs andirrigation extract river water.

17FACTORS AFFECTING FLOOD HYDROGRAPHSThe response of the drainage basin to an event (period of rainfall) will vary according toa number of factors:

Elongated (longer time for flow to reach main channel)

Circular (less time for flow to reach main channel)

Smaller (less time for flow to reach main channel

Larger (longer time for flow to reach main channel)

High. Lots of tributaries will shorten lag time

Low. Fewer tributaries will increase lag time

18USES OF WATER

Use IssuesAgriculture • Largest use of global water

• Agriculture can cause eutrophication of supplies (build of nutrientscausing algal blooms)

• Improper practices can lead to salination of supplies (evaporation)and a decline of groundwater supplies in wells and aquifers

• Possible conflicts over water are a realistic threat e.g. Middle EastIsrael v Jordan-over water extracted from the River Jordan andMexico v USA over Colorado river water.

• Drying up of water supplies e.g. Aral Sea in Asia, Lake had (Africa)have virtually disappeared

Industry • Most industries e.g. paper, wood, metals, steel, chemicals, plastics,fuels require significant water inputs

• Pollution from wastewater- thermal, heavy metals, effluents andeven radioactive waste water (nuclear power station)

• HEP schemes can regulate floodwater and provide cheap,renewable supplies of electricity, but building dams requires the lossof farmland and settlements, they can also silt up which damagesmachinery and change ecosystems downstream

• Mining and oil /gas extraction (fracking) also major user of water

Domestic • 3 billion people globally have restricted supplies (1 month disruptionper annum) and 1.2 billion lack access to clean water. This cancause disease and ill health and restrict quality of life

• By 2030 70% of global population faces water shortages (madeworse by water shortages)

• Variations in global use (USA - 400 litres per day, UK only 150).Richer nations tend to dominate, need for water conservation

Leisure & Recreation

• Water use in hotels, cafes, restaurants and in parks and gardens• Wetland areas under threat from coastal resort developments

The table below outlines the main uses of water

The distribution of water supplies is very uneven with some area having a surplusand others having a deficit. It is unusual for areas with the largest demand to be insurplus. Possible solutions to this include:

• Desalination schemes, removing salt from seawater for domestic use• Water conservation schemes, using improved technological efficiency and

education schemes to reduce water use in the home and the workplace• Water transfer schemes - building pipes, aqueducts and canals to transfer water

between areas of surplus and deficit e.g. Colorado river feeds both the CentralArizona Project and the All-American Canal (California). These are essential butexpensive projects, which can increase water losses by evaporation and seepage

The hydrogen economy is a proposed system of delivering energy using hydrogen forheating and powering vehicles. However hydrogen does not occur in its pure form onEarth and has to be extracted using a number of methods, including:

• Steam reforming. Steam is combined with natural gas and heated to around1,000°C and passed over a catalyst (e.g. Platinum) to reduce it to more usablecomponents including hydrogen gas

• Coal gasification. Coal is pulverised and heated to over 1,800°C with steam toproduce syngas which can be separated into other gas, including hydrogen

• Electrolysis. A current is passed through a water or alkali solution which producesboth hydrogen and oxygen at different electrodes.

Once the hydrogen gas has been produced it can be stored or transported.Hydrogen fuel cells (HCFs) are electrochemical devices that combine hydrogen andoxygen to produce electricity, with water and heat as its by-products.

The table below shows the advantages and disadvantages of the hydrogen economy

THE HYDROGEN ECONOMY 19

Advantages of Hydrogen Economy Disadvantages of Hydrogen Economy

• HCFs are more efficient thantraditional engines (80% to 30%efficiency comparison)

• HCFs have less moving parts than acombustion engine, and are morereliable and quieter

• HCFs do not degrade and canprovide a continuous source of powerunlike batteries which will eventuallylose charge

• HCFs are typically more portablethan combustion engines, locations

• HCFs are easier to install, reducingcosts for users

• Very high cost of extracting the hydrogenfrom steam reforming or gasification(high energy inputs)

• The reduction in greenhouse gasemissions via HCFs may be offset byhow the hydrogen gas was produced inthe first instance;(using fossil fuels)

• Initial HCFs were extremely expensiveand large, (new mass produced fuel cellshould reduce costs). A family carrunning on a HCF costs over £60,000.

• Fuel cell technologies are not fullydeveloped and it may be another 15 or20 years before the technology becomeswidespread

• There is a lack of infrastructure such ashydrogen fuel stations and maintenanceoutlets to support a changeover fromvehicles powered by petrol or diesel

ATMOSPHERE: STRUCTURE 20

The atmosphere can be divided into a number of recognisable layers: the troposphere;stratosphere; mesosphere, thermosphere and the exosphere at the edge of outer space.

The troposphere is the area where all life is supported and where all weather occurs. Itis composed of around 78% nitrogen; 21% oxygen; 1% argon and trace amounts ofwater vapour and carbon dioxide (0.04%).

• 26% is reflected by the atmosphere (18%by clouds and 8% by dust and gases)

• 6% is reflected from the earth’s surface• 18% is absorbed by the atmosphere

(clouds, water vapour and gases)• Only around 50% of the solar energy

(known as insolation) is absorbed by theearth’s surface:

The total amount reflected (around 32%) isknown as the Earth's albedo. This is higher inpolar areas where the whit surface reflectmore solar energy than the darker forests andoceans in the tropics

THE GLOBAL ENERGY BUDGETThe earth receives radiation from the sun, but only a proportion of this reaches theearth’s surface. Not all regions receive the same amount of radiation (sunlight)

GLOBAL DIFFERENCES IN INSOLATION

Tropical latitudes receive more insolation (solar energy) than polar latitudes:

Reasons

• Curvature of the earth means that solarenergy is concentrated at the tropics -smaller area to heat up; less heatingoccurs at the poles

• Solar energy has to travel through agreater depth of atmosphere at the poles- more absorbed by clouds, gases

• Reflection from the polar ice caps (thealbedo effect); more is absorbed bydarker rainforests

• Sun at a low angle for much of the year

There is a net gain (surplus) ofenergy in tropical areas and a net loss(deficit) of energy at polar areas.Higher latitudes have polar ice capsand a much of these altitudes areoceans which reflect solar energymore readily. There is no insolation inwinter months at the poles due to 24hours of darkness

surplus at tropics

polar deficit

21

CLIMATIC VARIABILITY

Climate is the average (or ‘normal’) pattern of weather for a particular place overseveral decades. Changes in climate are hard to detect without very long-termrecords.Climate Variability generally refers to natural fluctuations within the climate system.This includes the El Niño/La Niña oscillations. The El Nino originates every so yearsor so and involves the warming of the eastern Pacific and the declining influence ofocean currents which can have dramatic influence on weather patterns around theglobe’Climate Change refers to the long-term anthropogenic (man-made) modifications ofthe Earth’s climate. Over the last century there has been a definite pattern ofwarming (up to 2°C in places) and many scientists believe this is due to the build upof greenhouse gases (e.g. carbon dioxide, methane, CFCs) trapping heat energyradiated from the Earth’s surface. These gases are linked to human activities,principally the burning of fossil fuels in power stations, industry and in transportsystems and also in agriculture and deforestation of the Earth’s forest cover. Thiscould have a significant impact on sea level changes as oceans warm they expandand on the melting of ice on land masses (Greenland, Antarctica) in addition to thethreats to ecosystems, biodiversity and agriculture across the planet.

ATMOSPHERIC CIRCULATION

There is a transfer of energy from the tropics (surplus) to the high latitudes (deficit).80% of this is through the atmosphere and around 20% is via ocean currents

Atmospheric circulation occurs due to differences in air pressure. There aredistinctive belts of air pressure air around the planet, including a low pressure areaaround the equator and high pressure areas at the poles. The surface winds on theearth’s surface are created as air moves from areas of high to low pressure. Thegreater the difference in pressure, the stronger the winds.

The air does not travel perpendicular to the equator. As the earth spins the CoriolisForce (created by the earth as it rotates) influences atmospheric circulation. In thenorthern hemisphere winds are deflected to the right, in the southern hemisphere theyare deflected to the left

22

3 circulation cells, the Hadley Cell (tropics), the Ferrel Cell (temperate latitudes) andthe Polar Cell in each hemisphere help to transfer heat from the areas of surplus tothose of deficit, although this is a complex process.

• Intense heating at the equator causes air to rise forming low pressure. This airtravels both north and south eventually descending at the sub tropical high zones(usually desert areas about 30°N and S of the equator)

• Air is sucked in from sub-tropical areas at the equator to replace this rising air• Cold, dense air sinks at polar latitudes creating high pressure. This cold air moves

outwards from polar areas to temperate latitudes• Warm air moves from sub-tropical highs to the temperate lows via the Ferrel cell

Atmospheric circulation is also affected by Rossby Waves, giant meanders in high-altitude winds (jet streams) which can influence the position of low and high pressurebelts which bring unseasonal weather to mid latitude areas.

OCEAN CURRENTSOceans cover 67% of the earth's surface, and receive 67% of the sun's energy. Theyhold on to this heat for longer than the land does and the ocean currents move thisheat around, from the tropics to higher latitudes.

23

Movement of Ocean CurrentsEnergy is redistributed in the oceans by ocean currents. Warm water is transferredfrom tropical latitudes to high latitudes and cool water is transferred from high totropical latitudes for reheating. In total, ocean currents transfer 20-25% of the globalheat budget.

In the North Atlantic, the ocean currents follow a clockwise pattern or gyre:

• The warm Gulfstream carries heat up the east coast of North America and crossesthe Atlantic as the North Atlantic Drift, which heats the air above it, keeping Britainmild in winter.

• Cooler water is carried back to the tropics by the cooler, deeper Canaries current• The Labrador current also carries cool water from polar latitudes southwards

In the South Atlantic, the currents follow a anti-clockwise gyre:

• The warm surface Brazilian current takes warm water southwards• Cooler water is returned to the tropics by the deeper Benguela current along the

west coast of Africa

24WAVE POWER

Waves are a result of the effects of wind on the oceans and seas. This windoriginates from the major source of energy to the planet: solar energy from the sun.

Wave power can be split into three main categories:

1. At shore - on the actual coastline , powered by breaking waves2. Near shore - within 15km of the coastline3. Off-shore - beyond 15km from the coast and usually in water at a depth greater

than 50m

There are a number of methods by which wave power can be harnessed:

• Buoyant Moored Device. This floats on the surface of the water or just below itand is moored to the seabed and rotates around a long linkage generating powere.g. The “Salter Duck” machine which requires a sea depth of at least 80m.

• Hinged Contour Device. This follows the motion of the waves; it creates powerusing the motion at the joints. It is commonly moored slackly to hold it in place.The Pelamis “snake” device was an attempt to pilot this type of technology.

• Oscillating Water Column. This works by using a column of water as a piston topump air and drive a turbine to generate power. This type of device can be fixed tothe seabed or installed on shore such as the “Limpet 500” device.

Wave power has number of advantages and disadvantages:

Advantages of Wave Power Disadvantages of Wave Power• Few greenhouse gas emissions• Renewable (energy source is the sunwhich powers the atmosphere andwinds)

• Huge energy potential , up to 40kW forevery metre of wave along the shore.This increases with distance off-shore

• More reliable than solar and wind -usually a swell out at sea

• Area efficient. 1 square km of oceancould power 20,000 houses

• Larger potential in winter when thereis peak electricity demand

• Reduced environmental impact off-shore (in contrast to other sources)

• At shore devices can help reducecoastal erosion

• High cost and lack of investment indeveloping the required technology (e.g.Pelamis Wave company folded in 2014),although costs could drop in future

• Aesthetic impact (unsightly) could impacton coastal tourism

• Maintenance costs (corrosive, saltyenvironments)

• Impact on shipping lanes• Lack of knowledge of impact on coastalecosystems (noise, construction) althoughmooring reefs could help create newunderwater habitats

• Best generating areas are usually moreremote from National Grid (cost ofbuilding infrastructure and connections)

In Scotland, current projects are small scale and likely to be restricted to west coastand island communities until more investment is encouraged in the technology