Geography Notes PDF

-Geog 151 Definition of geography:  Spatial and temporal dimensions of the earth system  Studies the relationship between the physical and social environment within the contest or space, place and time.  Spatio has to do with space  Temporal has to with time Fun...

-Geog 151 Definition of geography:  Spatial and temporal dimensions of the earth system  Studies the relationship between the physical and social environment within the contest or space, place and time.  Spatio has to do with space  Temporal has to with time Fundamental questions in geography: geographers ask the questions why? What follows? For example why is it that the south west of Ghana has the most diverse vegetation? This requires explanation. Why did the vegetation occur in this region probably it might have passed through certain processes. The function of time (what, where, how) is another fundamental questions of geography. Natural laws governing the physical environment In the physical environment there processes and structures; processes lead to a pattern which are either ordered or irregular. Example clouds are formed from processes.  Natural processes can result in a pattern. Also human activities can also result in a pattern. For example a well planned residential area is a regular pattern and a slum are is an irregular pattern.  The physical environmental system is subjected to natural laws. These laws govern and control the processes and outcomes in the form of spatial structures of the earth system. For example the law of gravity, the law of conservation matter 1 What is the difference between weight and mass? F=ma The law of conservation of matter states that matter cannot be destroyed nor created but can be transformed from one state to another. Example water transformed from one state to another as in water to ice back to water and then to gas. Per these phases of change, matter is neither created nor destroyed. System Theorey What is a system? A system is a collection of elements or components that consists of interrelated and interdependent elements.These elements continually influence one another (directly or indirectly) to maintain their activity and the existence of the system... A system's input is defined as the movement of information or matter-energy from the environment into the system. Output is the movement of information or matter-energy from the system to the environment. Both input and output involve crossing the boundaries that define the system. When all forces in a system are balanced to the point where no change is occurring, the system is said to be in a state of equilibrium. Systems operate through differentiation and coordination among its components. A closed system is one where interactions occur only among the system components and not with the environment. An open system is one that receives input from the environment and/or releases output to the environment. The basic characteristics of an open system is the dynamic interaction of its components. Open systems can tend toward higher levels of organization (negative entropy), while closed systems can only maintain or decrease in organization. 2 Spheres of the earth system The earthy system is divided in to four spheres;  Lithosphere  Hydrosphere  Atmosphere  Biosphere Hydrosphere; the hydrosphere is studied by geographers to analyse the scientific study of the distribution of water on the earth surface, the flow and the processes they perform on the earth surface. Under the hydrosphere are the oceans – large water body usually dissolved in minerals and other compounds holding the boundaries of continents of the world for example pacific oceans, Atlantic oceans, Indian oceans etc. There are also seas found the boundaries of countries and continents. Examples are Dead Sea, Mediterranean sea etc. Lithosphere; plastic part of the earth’s crust. Liquid and solid composition of the earth and its crust takes a cross section of this layer. They are marked on the basis of the material core or material – molten- plastic. Within the earths crust density increases with increasing depth. Continents move in response to the molten and plastic materials. Pressure within the earth’s crust is released through an opening or a crack. If the pressure released is not intense then we have what is called earth tremor. On the contrary if the pressure released is so intense then what happens is what is called volcanicity. Processes that occur on the earth surface and within the earth are all functions of natural laws. These are forces that are responsible for processes and happenings on and within the earth’s surface. They include tensional and compressional forces. These forces are responsible for the 3 movement of the earth crust. Compressional force results forces from opposite directions. When the forces are equal in magnitude, they produce symmetrical landforms. Also when the forces from opposite directions are not in equal magnitude they produce asymmetrical land forms. In 1915, the German geologist and meteorologist Alfred Wegener first proposed the theory of continental drift, which states that parts of the Earth's crust slowly drift atop a liquid core. The fossil record supports and gives credence to the theories of continental drift and plate tectonics. 4 Atmosphere; it is an ocean of air surrounding the earth. It consists of a mixture of different gases. Different gases have different …….. resulting in pressures. The sum of different air composition exerts pressure resulting in atmospheric pressure. The physical and chemical characteristics of these ….. enables them to behave unequally from other gases. Different types of gases; nitrogen gas (N2), hydrogen gas (H2) etc The carbon dioxide gas is minute in the atmosphere but has effects because of its organic nature as far as climate is concerned.  Inert gases – non active gases.  Water vapor varies from place to place over time.  The atmosphere is divided into two main proportions.  The area with homogeneous mixing of the gases is called the homosphere (from the ground to a height of about 85km).  The area with unequal mixing of gases is called the heterosphere. It covers a distance of 85 km and above. Some elements drive the atmospheric processes. These elements include; temperature, pressure, humidity, winds etc. Temperature: Weather and climate occurs in the homosphere. One of the elements that drive the forces in the atmosphere is temperature-the measure of hotness and coldness of a place. So what then is heat? It is form of energy generated when particles are set in motion. These particles may collide. Temperature (𝑡 𝑜 ). The thermograph is an instrument used for the continuous measure of temperature. Measuring temperature momentarily done with the thermometer. The unit of 5 measurement of temperature is the degrees Celsius (00 𝐶), Kelvin (k) etc. one can covert one unit 32 of measurement to another for example,𝐹 − 1.8 = 00 𝐶,𝐾 = 00 𝑐 etc. Pressure: Pressure is another element of climate. What then is pressure? It can be defined as the force exerted per unit area. Pressure the atmosphere exerts is called the atmospheric pressure. There are individual gases that exert pressure. The sum of these partial pressure results in atmospheric pressure. The next question is how is atmospheric pressure measured? It is measured with an instrument called barometer and the unit of measurement is Pascal (𝑃𝑜 ), Bars, Milibars etc. the continuous measurement of pressure is done with the instrument called Barograph. Humidity: This is the measure of the amount of water vapour present in the atmosphere. Its measure could be in relative humidity, absolute humidity or mixing proportion. Absolute humidity measures the mass of water vapour to the total volume of air. Specific humidity measures the actual mass of water vapour to the total volume of air. Mixing ratio takes care of dry air. The mixing ratio is just like the specific humidity which is equal to the mass of the moisture divided by volume of dry air. Relative humidity measures the amount of water vapour in the atmosphere in relation to what the air can hold to become saturated. Winds: It is the air in motion in the atmosphere. Why do air moves? Pressure difference in the atmosphere creates pressure cells which causes air to move. A large body of air is called air mass. Air masses move from pressure cells classified as low or high. In the cause of movement, the air masses assumed physical characteristics of the changes in temperature composition of the areas they move. Measurement of wind direction is done with an instrument called wind wane. Aircraft takes off against the direction of the wind to let them take off. The aircraft flies in the stratosphere. 6 Lithosphere-solid part of the earth The earth crust is made up of interior part of the earth. The earth’s core is made up of the inner and the outer core. It has a thickness of about 1300km. the mineral components of the core are Nickel and iron (NiFe). The layer surrounding the inner core is the outer core. This layer has a thickness of about 2,250km. The next layer after this is the mantle. It a thickness of 2900km.the outer crust has a thickness ranging from 8 to 40 km. In between the mantle and the outer crust is the mohorocivic discontinuity. In the outer crust there are two main types of rocks masses namely SiAl and the SiMa. The SiAl flows on the SiMa simply because of the relative density we have the principle of isostacy. That is the balance established after the outer crust has undergone any form of denudation. SiAl is removed gradually and deposited somewhere to balance as in those eroded materials deposited in basins or depressions and exert some form of pressure to let the material adjust. All denudation and adjustment processes are geared towards equilibrium. Denudation means all processes that lead to the formation of landforms for example denudation and aggradations. Gradations come in two forms namely degradation-removal of land forms through mass movement erosion etc and aggradations-the building of new land forms. Rocks and minerals What are rocks? Rocks are formed by the aggregation of different minerals in the interior of the earth. These could be two or more individual minerals. Minerals found in isolation (ores) not in combination of other elements are Cu, gold, Iron ore etc. What are then minerals? They are naturally occurring inorganic solid substance with a definite chemical composition and uniform atomic structure which is made up of elements. Minerals 7 exhibit physical and chemical characteristics. Two types of minerals can be classified in terms of their mineral composition. Mafic Rocks; made up of magnesium and iron. This can also be called ferromagniseium rocks. They appear to be dark in color. Felsic rocks; also called feldspar and is made up of calcium (Ca) and potassium (K). It also orthoclase and they appear whitish in color. Characteristics of mineral rocks  Cleavage; ability of a mineral rock to break in response to some form of pressure. By their chemical composition, they have peculiar bonding. There could be could be stronger bonds and weaker bonds. For example ironic and covalent bonds. Some of the rocks break in different directions which is common in our environment. They are in layers like concoidal breaks.  Hardness; it determines it ability or otherwise to withstand pressure resulting in the breakdown of minerals in the rock and it measured on the Moho’s scale. Some minerals are soft such that one can just scratch it with the fingers. Others too are very hard such that they cannot be easily broken.  Colour of rock; it is emphasized by Mafic and Felsic rocks. The three main classes of rocks The three main classes of rocks include igneous, sedimentary, and metamorphic rocks. Igneous rocks are formed when molten magma from the earth’s interior solidify and cool within the crust or on the surface of the earth. On the basis of location, igneous rocks are classified as intrusive, extrusive or plutonic igneous rocks. 8 Plutonic igneous rocks can be found beneath the earth’s crust. This type of rock can be identified on the basis of rock texture-mineral aggregation. They undergo gradual cooling and solidification. The mineral composition of this type of rock gets enough time to form, so the texture is fine as in the case of granite, diolite, and gabbro. Extrusive igneous rocks are formed on the surface of the earth. Their exposure to the atmosphere enables them to undergo rapid cooling and solidification as in the case of phylite, andesite etc. these rocks could also be termed as coarse textured rocks. Some intrusive volcanic landforms include a dyke, lacolith. Sedimentary rocks are formed when already existing rocks like sedimentary and metamorphose rocks undergoes weathering, transported and deposited in depressions or chemically formed from precipitate in solution. Transportation and sedimentation occurs in layers. These layers are lithified into strata or stratum. They are also found in different layers of texture as in fine coarse etc. they so fine that they dissolve in solution. Examples include sandstone, limestone shale etc. Metamorphic rocks are formed when the chemical properties of the original rocks are changed into new rock form. These rock types change their physical condition as a result of temperature and pressure difference. Intrusive igneous rock comes into contact with other rock and due to intense heat form magma; the rock changes its form. Metamorphism could take the form of regional metamorphism which occurs as a result of mountain building. This happens when pressure exerted from compressional and tensional forces changes the rock physical structure. There are foliations in the rock. Key element used to identify metamorphic rock is its foliation. That is pressure exerted on the rock changes its structure. Sandstone changes to quartz; limestone changes to marble etc. foliated metamorphic rocks takes place within the earth’s interior under extremely high pressure that are unequal, occurring the pressure that is exerted is greater in one direction than in others (directed pressures). This causes the minerals in the original rock to reorient themselves with the 9 long and flat minerals aligning perpendicular to greatest pressure direction. Slate forms at a very low temperature and pressure along parallel planes. Weathering of rocks This could be defined as the chemical and physical disintegration of rocks insitu. Weathering could take the form of physical or mechanical as well as chemical decomposition rocks. The derived type of weathering of weathering from both physical and chemical weathering is termed as biological weathering. Physical processes physical of weathering Physical weathering processes can be grouped into thermal expansion, frost action, pressure release etc. Under thermal process of physical weathering, rocks expand and contract. With different minerals having different coefficient of expansion, the heat and cool at different rates causing exfoliation. Frost action normally occurs in the 10