Systems - Feedback & Equilibrium

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Information about Systems - Feedback & Equilibrium

Published on January 5, 2010

Author: arvindtirkey


Slide 1: Arvind Tirkey (Department Of Geography) 1 W E L C O M E TO SYSTEMS IN PHYSICAL GEOGRAPHY : SYSTEMS IN PHYSICAL GEOGRAPHY Systems Flow system – Open and Closed Matter Flow system Feedback and Equilibrium in Flow system Negative and Positive Feedback in maintaining the Equilibrium 2 Arvind Tirkey (Department Of Geography) SYSTEMS : SYSTEMS Set or collection of things that are somehow related or organized. Example – Solar System Arvind Tirkey (Department Of Geography) 3 Scheme for naming things. Example – Climate System or soil classification system SYSTEMS – FLOW SYSTEMMatter, Energy or both, move through time from one location to another : SYSTEMS – FLOW SYSTEMMatter, Energy or both, move through time from one location to another MATTER FLOW SYSTEM A Superhighway system of interconnected freeways and expressways. Individual roadways serve as pathways or tracks for flow of vehicles. Roadways are connected by interchanges that permit vehicles to move from one roadway to another. Vehicles on the roads and interchanges are part of the system. Vehicles are tangible objects – pieces of matter – that are in motion in the superhighway system. ENERGY FLOW SYSTEM Flow of Solar Energy from the Sun to the Earth and its atmosphere. Arvind Tirkey (Department Of Geography) 4 FLOW SYSTEM : FLOW SYSTEM Pathways – Path through which matter or energy or both flow/move through time from one location to another. Flow systems have a structure in which pathways of flow are connected. e.g. For the superhighway system, the individual roadways are the pathways. However, pathways of a natural system are not always quite so obvious. e.g. reflection of solar radiation from the top of a bright, white cloud. Structure – Patterns of the pathways and their interconnections as the structure of the system. Components – Parts of a system, such as the pathways, their connections, matter or energy within the system. Arvind Tirkey (Department Of Geography) 5 Slide 6: Inputs – The flow of vehicles fed in by on-ramps is the input. Outputs - The flow of vehicles leaving the system by exit ramps is the output. Power Source – Flow system needs some sort of power source. Motor fuels burned by cars, trucks, and motorcycles on the highway are the power source. Arvind Tirkey (Department Of Geography) 6 NATURAL FLOW SYSTEM : NATURAL FLOW SYSTEM Arvind Tirkey (Department Of Geography) 7 Powered by NATURAL FLOW SYSTEM EXAMPLES : NATURAL FLOW SYSTEM EXAMPLES RIVER SYSTEM Matter flow system of water in a set of connected stream channels. The stream channels (pathways) are connected in a structure (the channel network) that organizes the flow of water from high lands to low lakes or oceans. FOOD CHAIN OF AN ECOSYSTEM Energy in the form of food flows among plant and animal components. Arvind Tirkey (Department Of Geography) 8 GLOBAL ENERGY BALANCE SYSTEM Heat of the Sun is distributed around the Earth by currents of warm water and moist air. The flow in this system is one of heat energy. Slide 9: Arvind Tirkey (Department Of Geography) 9 OPEN & CLOSED FLOW SYSTEMS OPEN FLOW SYSTEM Where systems receive inputs and transfer outputs of energy and/or matter across the boundaries between them. Most natural systems are open ones. CLOSED FLOW SYSTEM There are no input or output flows of matter between the system and its surroundings. Flowing material in the system move endlessly in a series of interconnected paths or loops. CLOSED FLOW SYSTEM : CLOSED FLOW SYSTEM EXAMPLE - Automobile Race. Vehicle move around the track, making loop after loop, powered by the flow of motor fuel in their tanks. Cars remains on the track, so there is no input or output flow of cars. This system requires a flow of energy to sustain itself – in this case, the refueling that occurs in pit stops. So although a material cycle may be closed, but energy flow system will always be open. CLOSED FLOW SYSTEM IN PHYSICAL GEOGRAPHY The loops in this system are flow paths of water in solid, liquid, and gaseous forms. Arvind Tirkey (Department Of Geography) 10 Hydrological Cycle MATTER FLOW SYSTEMIs it an open or closed system? : MATTER FLOW SYSTEMIs it an open or closed system? It depends partly on where we draw the boundary around the system. A single river network as a simple system. Water enters the network (input) when it falls on the land as precipitation and exits from the network (output) at the river mouth, where it enters the ocean. Thus, this river system is an open matter flow system. New pathway can be added to make this system a closed matter flow system. If the return flow of water from the oceans to the atmosphere by evaporation is added then there is no input or output because water does not leave the Earth or enter from space. Thus the river system is closed. Arvind Tirkey (Department Of Geography) 11 Slide 12: Arvind Tirkey (Department Of Geography) 12 ENERGY FLOW SYSTEMIs it an open or closed system? They are always open system. All object emit radiant energy, and some fraction of that energy ultimately leaves the Earth i.e. output energy flow. All objects also absorb some portion of the radiant energy they receive (solar energy), so there is always energy input flow. FLOW SYSTEM : FLOW SYSTEM FEEDBACK Feedback in a flow system occurs when the flow in one pathway acts either to reduce or increase the flow in another pathway. Positive Feedback – Squealing noise made by a public address system. Too loud voice reaches the microphone and re-amplified. The process repeats itself making sound louder and unpleasant squeal. Here the process reinforce the flow of sound energy in the pathway between the microphone and the speaker. Negative Feedback – Thermostat that controls a home heating system. When the heating system is on, the room warms. When the warming trips a temperature-sensitive switch, it turns the heating system off. Here the heat flow from the furnace provides a negative feedback that reduces its amount. EQUILIBRIUM A steady state in which the flow rates in the various pathways of a system remain about the same. A lake within a closed basin in an arid climate – like the Great Salt Lake, Utah. Arvind Tirkey (Department Of Geography) 13 DIAGRAM 1 DIAGRAM 2 More examples……. : More examples……. Positive Feedback If a pond ecosystem became polluted with nitrates, washed off agricultural land by surface runoff, algae would rapidly grow in the pond. The amount of dissolved oxygen in the water would decrease, killing the fish. The decomposers that would increase due to the dead fish would further decrease the amount of dissolved oxygen and so on... Negative Feedback A good supply of grass for rabbits to eat will attract more rabbits to the area, which puts pressure on the grass, so it dies back, so the decreased food supply leads to a decrease in population because of death or out migration, which takes away the pressure on the grass, which leads to more growth and a good supply of food which leads to a more rabbits attracted to the area which puts pressure on the grass and so on and on.... Arvind Tirkey (Department Of Geography) 14 EXAMPLES OF AN EQUILIBRIUM SYSTEM A lake within a closed basin in an arid climate : EXAMPLES OF AN EQUILIBRIUM SYSTEM A lake within a closed basin in an arid climate Case – A No stream outlets and would dry up if not fed by streams. Water enters the lake from rivers and streams that feed it, while water leaves the lake by evaporation. Case – B If climate becomes a bit wetter and the input of the rivers increase. The water level rises, and the area of lake expands. Larger the lake area, greater is the evaporation. Eventually, the level rises to the point where the increased evaporation rate equals the increased inflow rate. That is, the level reaches an equilibrium. Arvind Tirkey (Department Of Geography) 15 Case – C If climate becomes arid again, the input reduces. Lake’s level will fall, surface area will decrease, and evaporation will decrease. Coupling between input, surface area, and evaporation can be recognized as negative feedback to maintain the equilibrium. Systems that come to an equilibrium are normally stabilized by negative feedback loops or pathways. ANOTHER EXAMPLE OF AN EQUILIBRIUM SYSTEMGlobal Climate System : ANOTHER EXAMPLE OF AN EQUILIBRIUM SYSTEMGlobal Climate System This system has numerous pathways of energy flow that include several important negative feedbacks. Thus, the global climate system tends to an equilibrium in which global surface temperature fluctuates around a mean. Like, low clouds are large white bodies reflecting sunlight back to space. This pathway tends to cool the surface, and so it acts as a negative feedback. High clouds absorb the outgoing flow of heat from the Earth to space and redirect it earthward providing a positive feedback that warms the surface. Arvind Tirkey (Department Of Geography) 16 Feedback & Equilibrium In A Coastal Area : Feedback & Equilibrium In A Coastal Area Most beaches are subjected to the alternating action of constructive and destructive waves. Constructive waves build up a beach and result in a steeper beach profile. This encourages waves to become more destructive (destructive waves tend to be associated with steeper profiles). However, as time goes by, the destructive waves transport sediment in a seaward direction, thus reducing the beach angle once more and encouraging the formation of constructive waves. This is a good example of a negative feedback in geography, where a process becomes less effective the longer it operates. It encourages the existence of an equilibrium state. Of course, in reality, an equilibrium state rarely exists because external factors (e.g. wind strength and direction are constantly changing. Arvind Tirkey (Department Of Geography) 17 TEST YOURSELF……. : TEST YOURSELF……. Explain what is meant by negative and positive feedback and then, with reference to one or more systems in a coastal area of your choice, give a detailed account of how these processes affect the stability of the chosen system(s). Explain the concept of negative feedback in maintaining the equilibrium, with reference to one or more systems in a coastal area of your choice. Arvind Tirkey (Department Of Geography) 18 ANY QUESTIONS : ANY QUESTIONS ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 19 Arvind Tirkey (Department Of Geography) Slide 20: Merci Danke gut Thank you Dhanyavad 20 Arvind Tirkey (Department Of Geography) Slide 21: Arvind Tirkey (Department Of Geography) 21 OPEN FLOW SYSTEM BACK Slide 22: Arvind Tirkey (Department Of Geography) 22 CLOSED FLOW SYSTEM BACK Slide 23: Arvind Tirkey (Department Of Geography) 23 BACK Slide 24: Arvind Tirkey (Department Of Geography) 24 NEGATIVE AND POSITIVE FEEDBACK Source: BACK REFERENCE : REFERENCE Books Ross, Simon, John Morgan, and Richard Heelas. Essential AS Geography. 1st ed. Nelson Thornes, 2000. Strahler, Alan, and Arthur Strahler. Physical Geography - Science And Systems Of The Human Environment. 2nd ed. Singapore: John Wiley & Sons, Inc., 2002. Images Arvind Tirkey (Department Of Geography) 25

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