BIOPHYSICAL INTERACTIONS Unit 1.1: An Introduction The four components of the biophysical environment:

• The atmosphere - the combination of gases andparticles enveloping the globe

• The lithosphere - the earth’s solid outer shell• The hydrosphere - the interconnecting system of

water storage in the atmosphere and lithosphere• The biosphere - the earth’s surface zone and

its adjacent atmosphere in which all organic lifeexists.

• Geographers are keen observers.• Most of the life on Earth occurs in the biosphere.• Contemporary industrial societies and technological advances are human impacts

which have affected global environments.

Unit 1.2: The Atmosphere What is the atmosphere?

• Gaseous layer that surrounds the earth• Consists of a mixture of gases: nitrogen, oxygen, carbon

dioxide and water.• Extends about 500km above the surface of the earth• The troposphere is the lowest level, and the next level is

the stratosphere (12 to 48km). The stratosphere containsthe ozone level.

• The ozone level protects the people by filtering harmfulultraviolet radiation emitted by the sun.

• There is concern about rising levels of carbon dioxide,methane, nitrous oxide and chlorofluorocarbons (CFCs).CFCs deplete the ozone layer.

Composition of the atmosphere: • Oxygen and nitrogen make 90% of the atmosphere’s volume.• The remainder comprises other gases (such as ozone and CO2) as well as pollutants and

particulates.• Increases in atmospheric concentrations of ozone-destroying gases and CO2 are now

major focus of scientific research.

Incoming solar radiation: The amount of incoming solar radiation depends on:

• The distance from the sun - the elliptical orbit of theearth around the sun can result in a 6% variation in theamount of insolation received.

• The latitude - incoming solar radiation has twice the areato heat at 60° north and south as it does at the equator.Therefore, temperatures are lower at higher latitudes.

• Length of day and night - Due to the earth’s axis, the shorter the day, the amountof absorption of incoming solar radiation is less.

The global heat budget: • A net gain in radiation everywhere on the earth’s surface except at the poles, which

have a high surface albedo• A net loss in radiation throughout the atmosphere• Horizontal transfers. Wind and ocean currents transfer heat from the tropics to the

poles. Winds account for 80% of the heat transfer, and ocean currents for 20%.• Vertical transfers. Heat is transferred to the atmosphere from the surface by terrestrial

radiation, conduction, convection currents and the transfer of latent heat viacondensation.

• As altitude increases, there is a decline in temperature called lapse rate.• The actual lapse rate varies from place to place, depending on air humidity. The rate

that applies at any given place and time is known as the environmental lapse rate.

Surface winds: • The sun heats the equatorial regions more quickly than the polar regions, causing

movements of air within the troposphere at a global scale.• Atmospheric pressure systems are areas of the atmosphere with relatively high or low

air pressure.• On the surface of the earth, some of the descending air moves back towards the Equator.

The cells created by this pattern of circulation are known as Hadley cells.• The Hadley cells produce descending air in the mid-latitudes on either side of the

Equator. This air moves back towards the equator as a surface wind. Air movingtowards the Equator is deflected to the left in the Southern Hemisphere and to the rightin the northern hemisphere by the Coriolis effect.

• High pressure systems result in anticyclones and weather conditions remain dry.• Low pressure systems are referred to as cyclones. There may be considerable amounts

of moisture. As moist air rises it cools rapidly and condensation and precipitation takesplace.

• An anticyclone is a large body of sinking air that produces an area of high pressure onthe earth’s surface. Because descending air warms, weather conditions remain dry.

• A cyclone is a large body of rising air that produces an area of relatively lowatmospheric pressure. As moist air rises it cools rapidly, condensation takes place andthe potential for precipitation increases.

• Tropical cyclones are intense low-pressure systems. They develop over warm tropicaloceans and their behavior is often erratic and unpredictable. Once they cross a coastlinethey turn towards the pole, their intensity is reduced, and they develop into what isknown as rain depression.

• An air mass is a body of air that has been affected by a large area of the Earth’s surface,such as an ocean or a continent. Ex. Maritime and continental air masses.

• A warm front develops when warmer or moister air is forced to rise over colder ordrier air.

• A cold front develops when advancing cold air undercuts a body of warm air.

Storms: • A severe thunderstorm has:- Hailstones with a diameter equal to or greater than 2cm- Wind gusts of 90km/h or more

- Flash flooding• Thunderstorms develop in moist air, an unstable atmosphere and a mechanism to

initiate their development.- Moist air is important because it condenses to form clouds.- Unstable atmospheric conditions allow developing clouds to rise to great heights in the

atmosphere.- The mechanisms that initiate thunderstorms are fronts, troughs and regions of low

pressure.• Severe storms occur when the atmosphere is very unstable, and the upward movement

of air is very rapid.• Several storm cells at different stages may be found within the same storm system.• Multicellular storms occur when several storm cells, at different stages of their life

cycle, are found within the same storm system. These produce hail, strong winds andflash flooding.

• A supercell is a rare but unusually severe type of thunderstorm whose structure,behavior, intensity and longevity are quite different from original thunderstorms. Thesemay produce very large hail, wind gusts and heavy rainfall.

The world pattern of climate: • The amount of solar radiation reaching the earth’s surface varies with latitude.• Near the equator, the sun’s rays are almost vertical and concentrated while near the

poles, the rays spread over a large area and results in solar energy per unit area.• As warmer air rises, it moves northwards and southwards, carrying heat away from the

equator towards the poles.• When the earth’s South Pole tilts towards the sun, the sun’s rays strike the Southern

Hemisphere more directly and intensely than in winter when the south pole is tiltedaway from the sun.

• The revolution of the earth also result in a variation in the length of night and day. Thelonger the day, the greater the amount of incoming solar radiation.

• In the troposphere, CO2 and water vapour are important in regulating temperatures.They let in the radiant energy of the sun but prevent some of it from escaping back intospace. This creates the natural greenhouse effect.

• As warm ocean currents experience relatively high rates of evaporation, the coastalareas nearby are likely to experience relatively high levels of precipitation.

• Cold ocean currents are accompanied by relatively low levels of evaporation, and theair above them tends to contain little moisture.

• Mountainous areas tend to be cooler than adjacent areas at lower altitudes.• Mountain ranges also interrupt the movement of prevailing winds and the movement

of moisture-laden air.• When moist air is forced to rise it cools and expands. This causes it to lose most of its

moisture as either rain or snow on the mountain ranges’ windward side. This producesthe rain-shadow effect or orographic rainfall.

• Results from the differential heating of the sea and the adjacent land surface.• Differences in atmosphere pressure, although small, are significant enough to initiate a

movement of air.

Unit 1.3: The Hydrosphere • Water is an integrating element in the biophysical environment because all components

require water to exist and develop.• Water can be found in solids, liquids or gases.

The Water cycle: • The water cycle is a process in which the

water circulates between the earth’soceans, atmosphere and land, involvingprecipitation such as rain and snow,drainage in streams and rivers, and returnto the atmosphere by evaporation andtranspiration.

• Condensation is the process by whichwater changes from a gaseous state backto a liquid state.

• Evapotranspiration is thetransformation of water from liquid togaseous state through evaporation ortranspiration.

• Infiltration occurs when the soilbecomes moist and absorbent due toprecipitation.

• Evaporation is the physical process bywhich moisture is lost directly to theatmosphere from a body of water due tothe sun’s heat or the effects of airmovements.

• Transpiration is the biological processin which water is lost from the pores of the leaves of plants.

• Precipitation results when large masses of moist air are cooled rapidly below dewpoint. With continued condensation, water droplets or ice crystals become larger andheavier. Eventually they become so heavy that the atmosphere can no longer supportthem, and they precipitate.

The global water budget: • The global water budget is the sum of the hydrosphere’s inputs, outputs and net

changes over a particular period of time.• The location, quantity and quality of water resources are largely determined by the

relationship between climate (precipitation and evaporation) and biological features,such as geology.

• Australia’s streamflow is meagre because the evaporation and transpiration are so high.

Global and continental variations in water budgets: • The total amount of water within the cycle is fixed but this water is unevenly distributed

both in terms of place and seasonal pattern.• The size of the continent produced extreme climates, with few areas of moderation.

• Australia has drifted into drier latitudes, the rainforests have flourished and spread, anda different Australia has resulted.

Flooding: • A flood occurs when the discharge is

greater than the capacity of the river channel.

• Discharge is the volume of water passing through a river in a specific period of time.

• There are different types of floods: - Slow-onset floods develop over a series

of days and last for one or more weeks.- Rapid-onset floods occurs more

quickly and in the mountain headwater areas of large rivers.

- Flash floods occur when intense storms drop large amounts of water within a brief period of time.

• A drought is a prolonged period of below-average rainfall that inhibits plant growth.• Droughts inhibit the growth of crops and natural vegetation. This can contribute to land

degradation. Wind erosion takes place when bare, dry soil is no longer bound togetherby the roots of trees, grasses and other plants.

• The Australian drought resulted in the casualty of the Snowy Mountains Scheme andsevere impacts of the Australian environment.

Unit 1.4: The Lithosphere

Continental drift and the origin of the continents: • Wegener’s theory is that, the currently isolated continents shifted laterally from a

former ‘supercontinent’.• The broken pieces of the supercontinent, could all fit back together.

• Geological investigations have shown that thesediments near the mid-Atlantic ridge are thin andrelatively young, while those progressively furtheraway are broken and older. This indicates that newland is being created along the mid-ocean ridges.

Plate tectonics: • Identification of the asthenosphere as a layer of weak, plastic-like material that acts as

a lubricating layer• Identification of the cold, rigid, lithospheric plates moving like great rafts over the fluid

atmosphere• The idea that if new oceanic crust is being continuously created along the mid-ocean

ridges

Causes of plate motion: • The rising magma at the diverging mid-ocean ridges is believed to push the plates apart

horizontally.

Plate movements: • Almost all of the tectonic and volcanic activity on the earth’s surface takes place at the

boundaries of the plates.• Horizontal movements create mountains, earthquake and volcanoes

Diverging plate boundaries:

Transform plate boundaries:

Converging plate boundaries:

Mountain-building: • Horizontal movements create mountains, earthquake and volcanoes• The world’s great mountain ranges coincide with the advancing edges of the earth’s

continental plates.• As the plates collide, the earth’s crust thickens in an effort to absorb impact. As it does

so, pressure is exerted and layers of rock are compressed and forced upwards, foldingand faulting as they go.

• Fold mountains are dominated by folded rock strata.• Faults are fractures in the rock structure. Rift valleys and block mountains are large-

scale landforms associated with faulting.

Earthquakes: • Earthquakes are a series of rapid vibrations caused by the sudden movements within

the earth’s crust.• A tsunami is a long, high ocean wave caused by an earthquake.

Volcanic activity: • The most active volcanoes lie in volcanic belts that coincide with zones where there is

fracture of, and collision between, the earth’s crustal plates.• Millions of tonnes of volcanic ash and smoke are released into the atmosphere reducing

the amount of sunlight reaching the earth’s surface.

Gradational Processes: • Gradational processes work to smooth out the surface• Exposed rock material is fragmented by weathering, detached by mass movement and

agents of erosion and then deposited at lower elevations as debris.• Gradational processes act upon the surface of the lithosphere, wearing down high places

and filling in low places.

Weathering: • Weathering is the physical disintegration and chemical decomposition of rocks and

minerals at or near the earth’s surface by atmospheric and biological agents.• Physical weathering slowly breaks up the rocks of the land surface into smaller

particles but does not change their chemical composition• Chemical weathering involves the actual decomposition of rocks, primarily by means

of exposure to water, oxygen and carbon dioxide. E.g. original minerals formed deepin the Earth’s crust.

Mass movement: • In some mass movements, the fragments of weathered material tend to stay together

and move as a unit in bulk.• The movement of material can be abrupt, as seen when landslide releases millions of

tonnes of material in a plunge.

Landforms Shaped by Water: Fluvial processes:

• Running water is effective in arid and semi-arid regions and where human activitieshave damaged the protective cover of vegetation that binds the soil together.

• Hydraulic action is the power of the flowing water. the surging water exerts a draggingaction on the river bed and banks.

• Abrasion occurs when rock particles that are carried by the swift-flowing current strikechannel walls.

• Corrosion is due to the chemical solution of material from rocks being exposed to thesteam by solvents carried in the river.

• Material can be transported as bedload, suspension load and dissolved load. the bedload is moved by traction (rolling, sliding and bouncing along the channel bed). Oncein the river, the sediment load may be temporarily deposited along the river’s banksuntil it is brought back into motion and moved further downstream.

Coastal landscapes: landforms shaped by waves: • Coastal terrains extend as far inland as the salt water, sea spray and wind-blown sands

reach, and into the ocean as far as the waves are able to move the material on the seabed.

Landforms Shaped by Ice: • Glaciers are huge masses of ice. they form when

snow that has accumulated over many years iscompacted to form glacial ice. Gradually, thequantity of snow becomes greater. Due to itsincreasing weight, the compacted glacial ice isforced to move outwards and downwards underthe force of gravity.

• Abrasion is when the surface of the land isscratched and worn down by the constantgrinding action of rock fragments that have been‘plucked’ from the ground and embedded in thebase of the ice.

• Erosional features:- U-shaped valleys- hanging valleys- cirques- arêtes- pyramidal peaks (horns)

• Depositional Features:- abrasion• Fiords are formed when rising sea levels

flood the valleys once occupied glaciers

Soils: • Soils with billions of microorganisms, bacteria

and fungi are vital for the conversion ofinorganic and organic material into the simplenutrients that are readily available to plants insoil water.

• Thus, soils provide a foundation for plant and,consequently, animal life on land.

Soil Characteristics: • Soil structure refers to how the particles clump

together in characteristic small masses calledaggregates or peds. Structure is vital for plantgrowth as it affects the rate of water absorption.

• Colour reflects the presence of identifiablesubstances in the soil. Dark colours occur wherethe humus content is high, and when it is lacking, soils are light. Some soils take on ared and yellow appearance in response to the oxidation of iron,

Soil Formation: • Parent material:- Soils consist of clay, silt, sand and organic material.- Most soils are formed from materials that have been transported and deposited. The

parent material provides a starting point for soil formation.- Siliceous parent materials, such as granite and sandstone, are relatively high in silica

and quartz. such as granite and sandstone. The soils derived from them tend to be lowin clay and of low fertility.

- Non-acidic parent materials, such as basalt, are high in ferromagnesian minerals. Theminerals are important for clay formation and so the soils derived from them are usuallyclayey and often fertile.

• Climate:- The ratio of precipitation to evaporation influences the amount of water available for

weathering, new mineral formation, leaching and the translocation of materials,especially clay.

- When rainfall exceeds evaporation, there is a net downward movement of water. Thisresults in eluviation or leaching.

- The drier the climate, the less water is available for these processes. Low temperaturesalso reduce weathering rates, but generally increase the rate of organic matteraccumulation.

• Topography- Well-drained soils occur upslope and that water-transported material accumulates on

the lower slopes and in depressions.• Organisms- Biotic activity can affect the type of soil occurring at a particular location, most notable

in surface soil layers. it also affects the different types of global vegetation.- Earthworms can also assist by ingesting soil and mixing it with organic matter, and by

constructing channels, which aerate the soil.• Time

Soil-forming Processes: • Water sinking into the ground takes with it both solid and dissolved matter from the

upper part of the soil and deposits it in the lower part. This contributes to thedifferentiation of soil into horizons, each with its own characteristics.

• This process is associated with:

- The leaching of soluble minerals, including calcium, magnesium, sodium, nitrate,chloride, sulfate and carbonate

- The movement and accumulation of organic matter, silicon compounds and iron oraluminium oxides

- Clay translocation, which is the movement and deposition of suspended clay particles.

Human interactions with the lithosphere: • Land degradation is the decline in the quality of natural land resources, commonly

caused by improper use. This is due to:- Agriculture- Mining- Forestry- Industry- urban settlement- tourism- infrastructure (roads,

railways, dams, power stations, pipelines and transmission lines)

Desertification: A global problem • Africa is vulnerable to desertification due to the

harsh climate. The marginally productive landbecomes easily sterile. Unreliable rainfall alsocontributes to desertification.

• Larger population numbers and lower rainfallhave upset this balance. It forces farmers to bringmore marginal land into production and toreduce periods of fallow.

• War and civil unrest have also played a majorrole in the degradation of the land. The spread ofdeserts is a global problem affecting two-thirdsof the world’s countries

Unit 1.5: The Biosphere Life on Earth:

• Life is possible due to all living (biotic) organisms(plants, animals and micro-organisms) and theirexcrement and dead remains.

• It also consists of the non-living (abiotic)environment, such as rocks, water and air.

• The biosphere incorporates and is the meetingpoint for the other three spheres. Every living thingis dependent upon this environment for its basicrequirements.

Ecosystems: • An ecosystem is a community of species and their

non-living habitat.

• The world’s ecosystems are dynamic. They respond to change, whether brought aboutby natural or human forces.

• The many ecosystems that exist can be broadly divided into two groups, aquatic andterrestrial. Aquatic ecosystems include life forms in marine environments (open sea,ocean inlets and coral reefs) and freshwater environments (rivers, lakes, dams andwetlands).

• Biodiversity is the variety of life, encompassing the different plants, animals andmicro-organisms, their genes and the ecosystems of which they form a part

• Endemic species are plants and animals that exist only to one geographical location.• Keystone species are dominant predators that allows a prey population to explode and

often reduced overall diversity. Other kinds of keystone species (coral or beavers)significantly alter the habitat and affects large numbers of other organisms.

• Dynamic equilibrium is a lack of change in a system so that inputs and outputs remainin balance.

Terrestrial ecosystems: • These are the major land ecosystems and comprise the communities of plants and

animals spread across the surface of the continents.• The biome is the largest recognisable subdivision in a terrestrial ecosystem. Biomes

recur on different continents in areas with similar climates.• The biomes are classified according to the characteristic vegetation within the

ecosystem due to the enormous biomass and vegetation forming the most conspicuouspart of the ecosystem.

Factors Affecting the Global Pattern of Vegetation: • Climatic, such as water supplies, temperatures, light and wind• Topographic, such as altitude, angle of slope and aspect• Edaphic (related to soils)• Biotic (related to the living environment)

Precipitation: • Water is very important for plant growth and development because it is vital to

processes such as photosynthesis.• Rainfall effectiveness is determined by:- Timing. Does it coincide with the growing season? Is it concentrated in summer when

moisture loss through evapotranspiration is high?- Intensity. Does it fall as steady, soaking rain allowing beneficial soil infiltration to

occur? When major storm events occur, how much water is lost as surface runoff?

Temperature: • Constant mean monthly temperatures above 16°C, accompanied by adequate

precipitation, produce optimum conditions for plant growth. Broadleaf evergreen treespredominate in tropical rainforests.

• If most of the rain falls in summer, when evaporation rates are especially high, there may be inadequate soil moisture to support trees, and grass-lands thus predominate.

• Areas which have low water availability produces smaller plaAntn se xspeamcpliea lolf y a afdaood ptweedb to reduce water loss and survive the effects of extreme aridity. The little rain that falls triggers a profuse growth of ephemerals.

• Seasonal variations in temperature and precipitation with five months below 6°C, or adry season, produce broadleaf deciduous forests.

• A period of more than six months below 6°C provides only a short growing season andconiferous, or boreal, forests dominate.

Light: • All green plants require light. Their leaves collect the sun’s energy and using it to

combine carbon dioxide with water to produce organic nutrients through the process ofphotosynthesis.

• The intensity of light determines the amount of energy available for photosynthesis.

Wind: • Wind affects vegetation through:- Physical damage- Asymmetrical shapes in plants- Reduction of moisture availability- Increasing the rate of transpiration- Transportation of pollen, spores and seeds

Topographic Factors: • With increasing altitude, there is a decrease in both soil depth and air temperature and

an increase in the exposure to wind.• The steepness of the slope is important because it influences the stability of the surface

material and the amount of water retained in the soil.• The orientation of a slope alters sunlight and temperature condition.

Edaphic (Soil-related) factors: • Most plants are dependent on soils as a medium in which to grow because soils provide

the water, air and nutrients necessary for growth.• If a plant moves downslope to alluvial soils, the vegetation would not be as good.

Biotic Factors: Relationship between plants and animals:

• A mutually beneficial (symbiotic) relationship would occur when species haveevolved together and are ultimately dependant on each other.

• Ex. Hummingbirds are highly specialised pollinators. They feed on concentratednectar, which fuels their high metabolism rate and their ceaseless hovering and darting.

Human activities: • Human activities are the most significant of all the biotic factors operating today. More

and more of the environment has been brought under direct human control. This hasbeen a result of the establishment of agriculture, the subsequent industrial developmentand an increase in human population.

Polar Bears: • Population of 22 000 – 31 000• 60 to 80% of the population live in Canada, while the rest live in Greenland, Norway,

Russia and United States.

• The polar bear feeds on ringed and bearded seals. They also eat walrus, beluga whale,bowhead whale carcasses, bird’s eggs, and rarely vegetation. They are the mainpredator of the environment.

• The destruction of their habitat due to climate change makes the polar bearsendangered.

• They are forced to go near Arctic coastal areas and communities.• Oil and petroleum spills are fatal to polar bears and affects the whole food chain.• Unsustainable hunting has also resulted in the deaths of many polar bears.• Scientists says that by 2035, the lack of sea ice will make it nearly impossible for polar

bears to survive.• Uncertain Future for Polar Bears – Stories – WWF• SUPER KILLER – POLAR BEAR

Yangtze River:• Environmental degradation has accelerated with increased economic development

since 1950.• Pollution levels have risen in the rivers and lakes• Soil erosion has occurred in the middle and upper basins caused by overgrazing and

over-cutting of trees. This has increased silt loads and land reclamation has reducedsurface area of lakes and wetlands.

• It is feared that the waters downstream from the dam, free of silt, will erodesurrounding banks and may cause land degradation.

• Numerous towns and cities have been inundated, forcing the relocation of one millionpeople.

• The Three Gorges Dam was built in 2003 based in the Yangtze and is the world’slargest power station in terms of installed capacity.

• The dam has the highest intensity of concrete placement but there are concernsrelating to silt accumulation, displacing local residents, ecological damage, loss ofheritage sites and earthquake risks.

• Yangtze River

Hydrosphere:

• Environmental degradation has accelerated with increased economic developmentsince 1950.

• Pollution levels have risen in the rivers and lakes• Soil erosion has occurred in the middle and upper basins caused by overgrazing and

over-cutting of trees. This has increased silt loads and land reclamation has reducedsurface area of lakes and wetlands.

• It is feared that the waters downstream from the dam, free of silt, will erodesurrounding banks and may cause land degradation.

• Numerous towns and cities have been inundated, forcing the relocation of one millionpeople.

• The Three Gorges Dam was built in 2003 based in the Yangtze and is the world’slargest power station in terms of installed capacity.

• The dam has the highest intensity of concrete placement but there are concernsrelating to silt accumulation, displacing local residents, ecological damage, loss ofheritage sites and earthquake risks.

• Yangtze River

• The Yangtze basin is well irrigated with average yearly rainfall amounts to about 1100mm. Most of the precipitation is brought by monsoon winds and rain in summer months.

• Floods, which result from monsoon rains in the middle and lower parts of the basin, usually begin in March or April and can occur at any time during the next eight months.

• Due to this, downstream waters become muddy and it is estimated that the Yangtze carries 280 - 300 million tons of alluvium to the mouth.

• Extensive flooding has occured 50 times and a catastrophic flood occurs every 50 to 55 years.

Atmosphere:• The Yangtze River basin is one of the world’s hotspots for nitrogen deposition.• This is due to pollution, formation of haze and use of ambient aerosols. • Carbon dioxide and methane are also found in abundant quantities. Carbon Dioxide

is derived from fossil fuel combustion and cement production. Methane comes from wetlands, rice paddies, energy production and biomass burning.

• This occurs around the Yangtze basin and it contributes to the existing atmospheric state.