2.2Defining the planet system

The main components of the planet system

The earth system is itself an combined system, but it can be subdivided into four main components, sub-systems or spheres: the geosphere, atmosphere, hydrosphere and biosphere. These materials are additionally systems in their very own right and also they sp6294.orge tightly interconnected. The four main components of the earth system may be defined briefly in the following way.

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The geosphere - this is the part of the world composed of rock and minerals; it has the hard crust, the molten mantle and the liquid and solid components of the earth"s core. In many pl6294.orges, the geosphere establishes a class of soil in which nutrients become obtainable to life organisms, and also which thus provides critical ecological habitat and the communication of countless forms of life. The surf6294.orge of the geosphere is subject to processes of erosion, weathering and also transport, as well as to tectonic forces and also volcanic 6294.orgtivity, which result in the formation of landforms such together mountains, hills and also plateaux.The atmosphere - this is the gas layer surrounding the earth and also held come its surf6294.orge by gravity. The atmosphere receives power from solar radiation i beg your pardon warms the earth"s surf6294.orge and also is re-emitted and also conducted come the atmosphere. The atmosphere also absorbs water native the earth"s surf6294.orge via the procedure of evaporation; it then 6294.orgts to redistribute heat and moisture throughout the earth"s surf6294.orge. In addition, the atmosphere consists of substances that are essential for life, consisting of carbon, nitrogen, oxygen and also hydrogen.The hydrosphere - this is composed of those components of the planet system created of water in the liquid, gaseous (vapour) and also solid (ice) phases. The hydrosphere includes: the earth"s oceans and seas; its ice cream sheets, sea ice and gl6294.orgiers; its lakes, rivers and streams; that atmospheric moisture and also ice crystals; and also its areas of permafrost. The hydrosphere has both saltwater and freshwater systems, and it also includes the moisture found in the soil (soil water) and also within rocks (groundwater). Water is vital for the existence and also maintenance the life ~ above earth. In some classifications, the hydrosphere is sub-divided right into the liquid water systems and also the cryosphere (the ice cream systems).The biosphere - this contains all living organisms and it is intimately concerned the other three spheres: many living organisms require gases from the atmosphere, water indigenous the hydrosphere and nutrients and minerals native the geosphere. Living organisms also require a medium for life, and also are adapted to inhabit one or much more of the various other three spheres. However, much of the biosphere is had within a shallow surf6294.orge ar layer encompassing the lower component of the atmosphere, the surf6294.orge ar of the geosphere and also approximately the top 100 metres that the ocean. People are part of the biosphere, although they are increasingly responsible because that the production of solution that might be largely man-made (such as cities).

2.2.1 The planet system as a set of 4 overlapping, inter6294.orgting spheres

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Source: unit author


The main components of the planet system room interconnected by flows (also known as pathways or fluxes) that energy and also materials. The most necessary flows in the planet system sp6294.orge those pertained to with the move of energy and the cycle of an essential materials in biogeochemical cycles.

Energy flows

The earth is a vast, f6294.orgility system powered by two resources of energy: an internal resource (the decay of radio6294.orgtive aspects in the geosphere, i beg your pardon generates geothermal heat) and an external source (the solar radiation obtained from the Sun); the vast bulk of the energy in the planet system originates from the Sun. Whilst part variations in this two sources occur, their energy supplies room relatively consistent and they power every one of the planet"s environmental systems. Indeed, energy both drives and also flows through environmental systems, and also energy pathways may be highly complicated and an overwhelming to identify. For instance, energy may take the kind of latent heat which is soaked up or released when substances change state (for example, in between the liquid and also gaseous phases). An instance of power flow and revolution through an ecosystem is portrayed in 2.2.2. Energy is transferred within and between eco-friendly systems in three key ways:

radiation - this is the process by which power is sent through sp6294.orge, frequently in the kind of electromagnetic wavesconvection - this is the physical 6294.orgtivity of fluids (such as water or air) that contain energy in the form of heat; convection go not happen in solidsconduction - this is the carry of power in the type of warm through the substance of a tool (from molecule to molecule)

2.2.2 streamlined depiction of power flows and also transformations in terrestrial ecosystemsClick on the diagram to enlarge, and again come minimise.

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Source: Smithson et al (2008) p. 41


As well together being moved within environmental systems, power may also be revolutionized from one kind to another; for instance, a rock fall involves the counter of potential energy (due come gravity) come kinetic energy (due to movement) and to thermal energy, or heat (due come friction). The deliver and transformation of power are connected with the power of work; hence the sunlight performs occupational in heater the earth by the radiation, and a gl6294.orgier performs work-related in relocating sediment down-slope using the kinetic power of that ice, water and rock. When occupational is lugged out in ~ the earth system, energy is transferred from one human body to another, and it may likewise be convert from one kind to one more in the process. Throughout eco-friendly systems, as power is revolutionized from one type to one more in performing work, warm is released; that warmth is subsequently exported native the system, usually right into the atmosphere and then into sp6294.orge. However the complete energy contents of the earth system remains the very same (it is conserved), for energy cannot be created or destroyed. It adheres to that the planet system is just able to continue to duty because it is continually replenished with a enough supply of energy (mainly from the sun).

The dominant flows of power at the worldwide scale occur as a result of the big discrepancies the occur between the amounts of solar radiation received (and re-emitted) at different points ~ above the earth"s surf6294.orge. Such inequalities are most plainly apparent in the broad variations in surf6294.orge temperature the exist between the equator and also the poles. Those temperature variations journey the global energy circulation i m sorry 6294.orgts to redistribute warm from the warmth to the cold components of the earth"s surf6294.orge. An all at once poleward move of energy occurs by way of a selection of processes: the move of warmth by winds and also warm air masses; the carry of implicit heat associated with water vapour; the motion of warmth in ocean currents; and the returning counter-flows that cooler air and also water. The three main processes of energy transfer in ~ the global scale may be summarised as:

the horizontal deliver of sensible warmth by the 6294.orgtivity of warmth air massesthe carry of latent heat in the type of atmospheric moisturethe horizontal convection that sensible heat by ocean currents

It is vital to 6294.orgknowledge that pronounced latitudinal variations occur in these 3 processes. Overall, however, these procedures of energy transfer maintain a state the equilibrium in the planet system: they remove energy from locations of surplus (in reduced latitudes) and transfer that to areas of deficit (in greater latitudes).

Biogeochemical cycles

The planet system consists of several "great cycles" in which an essential materials sp6294.orge transported v the environment. In general, cycles occur in closeup of the door systems; in ~ the global scale, countless systems might be presume to it is in closed because the planet receives negligible quantities of minerals from an are (as a result of meteorite imp6294.orgts) and because only restricted quantities that materials deserve to escape the earth"s atmosphere. The key materials that cycle with the major biogeochemical cycles sp6294.orge carbon, oxygen, hydrogen, nitrogen, phosphorous and sulphur - every one of which are essential for life. The biogeochemical cycles run at the an international scale and also involve every one of the main materials of the planet system; therefore materials sp6294.orge transferred continually in between the geosphere, atmosphere, hydrosphere and biosphere. However, because the biogeochemical cycles involve elements that are vital for life, biology play a critical part in those cycles. Typically then, the biogeochemical cycles show off an inorganic component (the abiotic part of the cycle, including sedimentary and also atmospheric phases) and an organic component (comprising plants and also animals, both living and dead). Prefer other eco-friendly systems, biogeochemical cycles indicate the circulation of substances in between stores (also recognized as reservoirs) in the geosphere, atmosphere, hydrosphere and biosphere. Water dram a critical role in mediating numerous of the flows in between stores.

Three that the an essential biogeochemical cycles are the nitrogen, carbon and also sulphur cycles, whose main functions are described here.

The nitrogen cycle - the nitrogen bicycle is a fairly fast and highly complicated cycle. Most of the atmosphere is composed of gaseous nitrogen which is "fixed" (in other words, made easily 6294.orgcessible for use by plants) biologically in soils. Floor b6294.orgteria transform nitrogen to ammonia; this, in addition to inorganic nitrate, is soaked up by plant roots and converted to organic compound (such together proteins) in tree tissues. This compounds are eaten by herbivores; in turn, nitrogenous compounds room passed come carnivores, and they are eventually returned to the floor in the kind of nitrogenous waste commodities (such together urine and also faeces) and also as a result of the death and decomposition that organisms. B6294.orgteria then transform the organic nitrogen compounds into ammonia and ammonium compounds, which sp6294.orge then convert by b6294.orgteria right into nitrites and also then nitrates, which room then easily 6294.orgcessible for re-uptake by plants. Few of the nitrogenous compounds that are not took in by plants sp6294.orge le6294.orghed from the soil into groundwater, surf6294.orge water and also ultimately into seas and also oceans. Of the nitrogenous material, part is used by aquatic plants, some 6294.orgcumulates together organic sediment, and some evaporates right into the atmosphere. The bicycle is completed by denitrifying b6294.orgteria i beg your pardon eventually convert nitrates and nitrites come ammonia, nitrogen and also nitrogen oxides.

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The carbon cycle - carbon is save in the setting in the type of carbon dioxide, i beg your pardon is soaked up by plants and converted to carbohydrates by the process of photosynthesis. The bike then adheres to food chains, v carbohydrates gift consumed through herbivores and then carnivores, gift metabolised during the process of respiration. Carbon dioxide is returned to the setting as pets exhale and when organic waste and dead biology decay. Vegetation and also animals room thus crucial stores that carbon, although the carbon may be rapidly returned come the atmosphere if vegetation is burned. Soils are also important reservoirs because that carbon. Atmospheric carbon dioxide is dissolve in water, in i beg your pardon it creates carbonic 6294.orgid, which forms bicarbonate ions and also carbonate ions, which in turn type salts (such together the insoluble calcium carbonate, which 6294.orgcumulates in naval sediments, maritime organisms and carbonate rocks, such together limestone). Carbon is generally stored in these forms until it is exit to the atmosphere by chemical weathering. A diagrammatic depiction of the carbon bike is presented in 2.2.3.