December 2, 2022

Processes operating in the interior of the earth resulting in the formation of natural physical features or landforms. They are caused by earth movements. Examples of these processes are folding, faulting and Vulcanicity. Formation of land forms by internal land forming processes is determined by: Nature and age of earth materials Type of movement involved Intensity and scale of movement involved Crustal Earth Movements Displacement of the earth’s crustal rocks. They are brought about by tectonic forces which originate and operate in the interior of the earth e.g. tensional forces (which operate along horizontal plane moving away from each other), compressional forces (which operate along horizontal plane moving towards each other), shear forces (which move past each other with unequal strength) and gravitational forces (which attracts things to the earths centre). Earth movements are of 2 types: Horizontal/lateral/orogenic movements Vertical/epeirogenic movements Horizontal Earth Movements Movements which act along a horizontal plane within crustal rocks. They are caused by tensional and compressional and shear forces. Effects They cause: Strain and stretching of crustal rocks due to stretching caused by tensional forces which cause formation of cracks or faults. Squeezing and shortening of crustal by compressional forces rocks which cause them which also cause formation of faults. Crustal rocks to shear by slipping past each other or by dividing into layers which is caused by shear forces. Results of Horizontal Earth Movements results in the formation of the following features: Faults Escarpments Rift valleys Basins fold mountains Tilt blocks Block mountains  Vertical Earth Movements Movements which occur along the earth’s radius or towards the earth’s surface or towards its centre. Effects Causes: Subsiding/sinking/downwarping or pulling of crustal rocks downwards. Uplifting/upwarping or pushing of crustal rocks upwards Tilting of crustal rocks or shearing in vertical direction due to grater uplift on one side. Results of Vertical Earth Movements Raised cliffs Plateaus Tilt blocks basins Rift valleys Fault scarps/escarpments Causes of Earth Movements  Magma movement within the earths crust. Gravitational force Convectional currents in the mantle Isostatic adjustment 1. Magma Movement within the Earths Crust When magma moves with force pushing crustal rocks horizontally or vertically. When magma moves from reservoir and leaves empty spaces onto which crustal rocks are pulled inwards. 2. Gravitational Force  When the attractive force of the earth pulls crustal rocks into empty spaces left after magma escaping from the reservoir. When convectional currents in magma in mantle drug crustal rocks by friction. Horizontal movement of currents cause horizontal movements while vertical cause vertical movements.  Isostatic Adjustment Rising of continental masses to restore the upset state of balance between sial and sima layers. Isostacy is the state of balance between sial and sima layers. It can be disturbed by erosion on continents and melting of continental ice sheets. The reduced weight causes continental masses to rise. Theories Explaining the Earths Movements A theory is reasoned ideas intended to explain facts or ideas. There are 2 theories which explain the earth’s movements namely the Continental Drift Theory and the Plate tectonics theory. Theory of Continental Drift Its proponent was A. Wegener. It explains the origin of 6 continents. It states: The earth was a single sialic land mass called Pangaea surrounded by a huge ocean called Panthalasa whose floor was a mass of sima. Pangaea broke into two parts called Laurasia (N. Hemisphere) which lay around equator and Gondwanaland (S. Hemisphere) which lay around south pole which were separated by a narrow ocean called Tethys (the present Mediterranean Sea). Laurasia broke into Laurentian Shield and Fennoscandia (Europe, Asia and N. America) and moved northwards to their present positions. Gondwanaland broke into Africa, Australia, S. America and Antarctica and India subcontinent. Africa and India drifted northwards. Evidences Supporting the Theory Fitting of western coast of Africa and S. America into a jigsaw. Discovery of coal 40◦N and 55◦N which was formed by burying of tropical vegetation. Considerable displacement of rocks along some faults e.g. along the Great Glen Fault of Scotland. Cape and Buenos Aires folds resemble one another by having east west trend. Red sea shores show evidence of having undergone lateral displacement an indication that it was formed by movement of the earth’s crust. Evidence of ancient Glaciation to the south of equator in Africa in Madagascar and India where there is presence of ancient glacial deposits suggesting these areas were once around south pole.    Plate Tectonics Theory It states that: The earths crust is made of blocks called plates. 7 Large Ones Eurasian plate N. American plate Australian plate S. American plate Africa plate Pacific plate Antarctic plate Smaller Ones Indian Arabian Caribbean Nazca Cocos Philippine Somali plates Scotia Juan de Fuca These plates are two types : tectonic plates: Oceanic plates which form major areas of the ocean floor including coastal lowland. Continental plates which form the bulk of the continental land mass. The plates float on molten mantle layer called The plates move relative to each other due to convectional currents in the mantle. They move away from each other forming extension or constructive boundary called so because magma fills the space between. They move towards each other forming compressional or destructive boundary called so because materials between are crushed. The movements of those two types of plates have the following effects: There is subduction and the ocean floor is pulled inwards forming a trench e.g. Java Trench . Subduction is the passing of edge of one plate beneath the edge of another. Sediments on the sea floor in the region of subduction are compressed to form Fold Mountains. When an oceanic plate meets a continental plate the edge of the oceanic plate slides beneath the continental plate in a movement called subduction. Sediments on the sea floor in the region of subduction are compressed to form Fold Mountains. Fold Mountains are also formed at the edge of the continent when the sial layer is compressed. The edge of the oceanic plate bends into the mantle forming a trench. When two continental plates collide the

TOPIC 1 : INTERNAL LAND FORMING PROCESSES NOTES – Click to view TOPIC 2 : FOLDING NOTES – Click to view TOPIC 3 : FAULTING NOTES – Click to view TOPIC 4 : VULCANICITY – Click to view TOPIC 5 : MAP WORK – Click to view TOPIC 6 : PHOTOGRAPH WORK – Click to view TOPIC 7 : CLIMATES – Click to view TOPIC 8 : VEGETATION – Click to view TOPIC 9 : FORESTRY – Click to view

Process of extracting valuable minerals from the earths surface. Formations in Which Minerals Occur 1. Veins and Lodes Occurrence of minerals in crevices, cracks or faults in igneous rocks. They are said to occur in veins if they occur there in small quantities. Said to occur in lodes if they occur there in large quantities e.g. zinc, copper and silver. 2. Reefs Veins and lodes which are exposed on the surface. 3. Seams/Layers/Beds Occurrence of minerals as sedimentary or as a result of compression of accumulated organic or inorganic material e.g. coal and halite. 4. Alluvial Deposits Occurrence of miner  als while mixed with materials such as sand, gravel, silt, etc. These were minerals which were detached from the veins by weathering and carried away by streams and rivers and got deposited e.g. gold, diamond and platinum. 5. Weathering Products Minerals formed by deep weathering of rocks then leaching carried minerals from the top to lower layers where they accumulated e.g. aluminium, nickel, iron and manganese. 6. Oil pools/Wells Occurrence of minerals in pools or wells in sedimentary rocks e.g. petroleum and natural gas. Presence of fossils or organic remains Presence of sedimentary rocks for burying organic remains. Presence of pressure to compress organic remains to cook the oil and natural gas out of organic matter. Presence of a porous reservoir rock to store and transmit petroleum to the oil pools e.g. limestone and sandstone. Presence of a trap like a syncline to hold petroleum in a reservoir to prevent its escape. Presence of impermeable rocks below the trap or syncline to prevent petroleum from percolating further underground. Factors Influencing Exploitation of Minerals 1. Value of Mineral Minerals of high value will be mined even if they occur in small quantities because one sold it will be possible to offset mining costs and make a profit and vice versa. 2. Quality of Ore Mining can be done if the mineral deposits have high mineral content because they are economical to work on but deposits with low mineral content are rarely worked on except if the mineral in them is rare e.g. uranium. 3. Size of Deposit Minerals which aren’t of high value have to occur in large quantities for them to be mined so that it will be a possible to recover mining costs and make a profit. 4. Capital Lack of capital causes developing countries not to exploit minerals and leave it to international companies because a lot of money is needed for exploration, infrastructure, salaries, energy etc e.g. titanium mining at Kwale is being done by Tiomin company from Canada. 5. Method of Mining A mineral requiring open cast mining will be mined even if the mineral deposit is large but one requiring underground mining will be extracted if its in large deposit or if its of high value or rare. 6. Transport costs Minerals occurring in remote areas far from the markets are not likely to be exploited if the transport system is poorly developed since mineral ore is heavy and bulky and transporting it by road and railway is expensive. 7. Market for the Mineral Mining can be done if the mineral is in demand and if the prices are reasonable so that mining costs are offset and a profit is realised. 8. Political Influence Mineral deposits at the borders of two countries may not be exploited as a dispute may arise concerning whom mine it e.g. dispute between Iraq and Kuwait over Rumaila should oil field. 9. Labour Exploitation of some minerals require skilled workers and if they lack it may not be done as is the case in developing countries because expatriates have to be engaged and are very expensive to pay which may reduces the profits accruing from mining. Methods of Mining 1. Open Cast Mining Method of extracting minerals which are near the earth’s surface. Types 1. Stripping -Stripping off of the unwanted material lying on top of the mineral deposit and then digging to remove the mineral bearing rock if it’s soft or if it’s hard explosives may be used to loosen it and then huge power shovels are employed to dig up the mineral deposits. 2. Hill-slope Boring Using boring instruments known as augers to drill out mineral deposit and bring it to the surface. 3. underground Mining Method employed when the mineral lies very deep below the surface and the overburden is too thick to be removed by mechanical means. Types Shaft Method Method employed when the mineral bearing rock doesn’t out crop. How it’s carried Out Vertical shafts are sunk into the earth’s crust to reach the layer with the mineral. Horizontal tunnels are dug from the vertical shaft to reach the mineral. Props are erected to support the roof to prevent it from collapsing. The mineral bearing rock is blasted loose by explosives. The deposit is transported on light rail or conveyor belt to the bottom of the shaft. It is then brought to the surface in a crane or a lift called cage. Drift/Adit Mining Method employed when the mineral deposit can be reached from the valley sides. Horizontal tunnels (adits) are constructed from the side of the hill. Railway line is constructed into the mine to bring out the mineral e.g. mining of copper at Kilembe in Uganda.  Solution Method Method used in mining soluble minerals such as sulphur, salt, potash, etc. Superheated water is ejected into salt deposits. The mineral dissolves or melts. The solution is then pumped into the surface. Drilling  Method employed in exploitation of petroleum. Wells (oil derricks) are drilled. Oil and natural gas are brought to the surface under their own pressure or by pumping. Alluvial/Placer Mining Method used to extract minerals occurring in alluvial deposits e.g. gold, tin, diamonds and platinum.  Types 1. Panning It involves: Digging a mixture of sand, gravel and mineral from the river bed. Putting it in a pan and rotating the pan while tilted. The lighter sand or gravel is washed on the

Inorganic substances occurring naturally at or below the earth’s surface. Characteristics of Minerals Different degrees of hardness e.g. some are very hard e.g. diamond while others are very soft e.g. talc. Some have atoms arranged in an orderly manner to form crystals e.g. quartz form a 6- sided prism. Varying number of elements e.g. gold has one (Av) while quartz has 2 (SiO2). Different abilities to allow light to pass through e.g. some are transparent, opaque or translucent. Specific colours e.g. gold is shiny yellow while copper is brown. Have specific surface appearance (lustre) when they reflect light i.e. metallic (shiny) or non-metallic (glass like). Definite chemical composition or constant ratio of elements e.g. quartz has one atom of silicon and two atoms of oxygen. Tendency to break along certain lines or cleavage) e.g. flint has cleavage like that of glass. Different densities e.g. some are very heavy e.g. lead while others are light e.g. silicate minerals. Some minerals conduct electricity while others don’t e.g. copper conducts while diamond doesn’t. Some can be pressed into different shapes while others can’t e.g. copper is malleable while flint isn’t. Types of Minerals Metallic minerals Ferrous Minerals-limonite, magnetite, siderite and haematite. Non-ferrous Minerals-copper, aluminium, gold, lead, etc. Non-metallic Minerals-graphite, diamond, asbestos, coal, etc. Energy minerals-petroleum, coal and uranium. Rocks –A consolidated material composed of grains of one or more minerals. Classification of Rocks 1. Igneous Rocks Rocks formed when molten material from the earth’s interior cools and solidifies on or beneath the earth’s surface. Types of Igneous Rocks 1. Intrusive Igneous Rocks Rocks formed when magma cools and solidifies below the earth’s surface e.g. granite, diorite, gabbro, peridotite. Have coarse texture as a result of slow cooling giving minerals more time to form large crystals. Are classified further into two: Hypabyssal rocks- intrusive igneous rocks which are near the earth’s surface. Plutonic rocks-intrusive igneous rocks which are deep below the surface. 2. Extrusive Igneous Rocks –Rocks formed when lava solidifies on the earth’s surface. Have fine texture due to fast cooling giving minerals less time to collect together to form larger crystals. They are of two types namely: Volcanic Ejecta -Extrusive igneous rocks formed in the following ways: When ash and lava ejected from underground as they fall on the earth’s surface e.g. pumice. When dust and ash ejected settle on the ground and get compressed to form a rock e.g. tuff. Lava Flows Extrusive igneous rocks formed when basic lava flows over a considerable distance then cools and solidifies e.g. basalt and obsidian. 3. Sedimentary Rocks Rocks formed when particles of other rocks are laid down and compressed into layers or when plant and animal remains are buried and compressed and compacted. When they are laid down a layer is formed. As deposition continues additional layers are formed which compress the lower layers into a hard mass. Types of Sedimentary Rocks Mechanically Formed Sedimentary Rocks -Sedimentary rocks formed when weathered igneous or metamorphic rocks are deposited and compacted e.g. sandstone and shale. Organically formed Sedimentary Rocks -Sedimentary rocks formed when animal and plant or animal remains are buried, compressed and compacted. Classification of Organically Formed Sedimentary Rocks Calcareous rocks-rich in calcium carbonate e.g. chalk and limestone. Coral rocks are formed from remains of sea polyps which extract lime from the sea, build shells for protection, attach themselves to each other and rocks to live in colonies, then die and shells to form coral rocks.    Ferruginous Rocks-rich in iron e.g. ironstone. Siliceous Rocks-rich in silica e.g. diatomite. Carbonaceous Rocks-rich in carbon e.g. coal. Chemically formed Sedimentary Rocks -Sedimentary rocks formed when materials dissolved in water chemically react forming new substances then water evaporated leaving layers of those salts. Classification of Chemically Formed Sedimentary Rocks Carbonates g. trona and dolomite Sulphates-sulphate compounds Chloridesg. halite (iv) Silicates e.g. flint Iron stones e.g. haematite and limonite. 4. Metamorphic Rocks Rocks which have changed their physical appearance and chemical properties as a result of subjection to great heat and pressure e.g. Gneiss from granite Slate from clay Marble from limestone Quartzite from sandstones Distribution of Major Rocks in Kenya Eastern Kenya region The major rocks are metamorphic rocks e.g. marble in parts of Machakos and schist and gneiss in parts of Kitui. Volcanic rocks in Yatta plateau and Kapiti plans. Sedimentary rocks e.g. limestone rocks used in Bamburi for cement manufacturing. Coastal Region Major rocks are sedimentary rocks e.g. limestone used in Bamburi for cement manufacture. There are volcanic rocks in Tsavo rich in ground water resources. Northern and N.E Region Dominated by sedimentary sands. There are volcanic rocks in Mt. Marsabit and around Rift Valley. Rift Valley and Kenya Highlands Dominated by volcanic rocks There are metamorphic rocks which have resulted from changing of igneous rocks. L. Victoria Basin Granite and gneiss dominate Western Kenya where they form high rocky hills called granitic tors common in Kisii, Maragoli and Bunyore areas. Sedimentary rocks deposited by rivers e.g. Nyando, Nzoia, Yala and Sondu. Significance of Rocks Rocks weather to form soil which is important in agriculture. Form aquifers which store ground water which forms springs which form rivers and wells which provide water for domestic and industrial use. Some rocks are sources of building materials e.g. igneous rocks are used to make ballast and limestone rocks are used as building blocks and raw material in cement manufacturing. Phosphate and nitrate rocks are used to make fertiliser used in agriculture. Granitic tors of W. Kenya and high volcanic peaks such as those of Mt. Kenya are a tourist attraction which brings foreign exchange. Pumice is used as a scrubbing stone. A rock such as coal is used as fuel for heating, smelting of iron and thermal electricity generation. Source of minerals e.g. oil and coal is associated with sedimentary rocks.

Daily atmospheric conditions of a place at a particular time. Elements of Weather Temperature Humidity precipitation Precipitation Atmospheric pressure Wind Sunshine Cloud cover A Weather Station A place where observation, measuring and recording of weather elements is done Factors to Be Taken Into Account When Sitting a Weather Station An open place where there is little obstruction of weather elements. Accessible place so that recording can be done easily. A fairly level or gently sloping ground (5◦) so that it’s easy to position weather instruments. The place should provide a wide view of the surrounding landscape and the sky. The site should be free from flooding. The place should have security. Instruments for Measuring Elements of Weather Thermometer-temperature Hygrometer-humidity Rain gauge-rainfall Barometer-air pressure Sunshine recorder-sunshine duration and intensity Wind vane –wind direction Anemometer-wind speed Evaporimeter-rate and amount of evaporation. A white wooden box mounted on 4 legs used to house thermometers and hygrometers. The instruments which are found in it are: Maximum thermometer minimum thermometer Six’s thermometer hygrometer-wet bulb and dry bulb thermometer Importance Provide shade conditions for accurate temperature recording. Ensure safety of thermometers because they are delicate. Qualifications Which Make Stevenson Screen Suitable For Its Work Painted white for little absorption of solar heat energy. Made of wood which is a bad conductor of heat. Well ventilated to allow easier flow of air inside it. Raised to prevent contact with terrestrial radiation. Has double roof which acts as an insulator to prevent direct heating from the sun. Recording and Calculating Weather Conditions Temperature -Degree of hotness of an object or a place. It’s measured using 3 types of thermometers namely: Maximum thermometer Minimum thermometer Six’s thermometer It’s used to measure the highest temperature reached in a day. It uses mercury. How It’s Used/Works Temperature rises causing mercury to expand. Mercury pushes the index up. When temperature falls mercury contracts. The maximum temperature is read from the scale at the lower end of the index. Thermometer is reset by shaking it to force mercury back into the bulb. It’s used to record the lowest temperature reached in a day. It uses alcohol. How it’s Used/Works Temperature falls causing alcohol to contract. Alcohol pulls the index down. When temperature rises alcohol expands and rises in the tube. The index remains where it was pulled. Minimum temperature reading is obtained from the scale at the lower end of the index. Calculating Temperature 1. Diurnal/daily Temperature range –Difference between the maximum and minimum temperature for any one day. 2. Mean Daily Temperature Average of the maximum and the minimum daily temperatures. 3. Mean Monthly temperature -Sum of mean daily temperatures in a month divided by the number of days in that month. 4. Mean Monthly minimum Temperature –Sum of daily minimum temperatures divided by the number of days in that month. 5. Mean Monthly Maximum Temperature -Sum of daily maximum temperatures divided by the number of days in that month. 6. Mean Annual Temperature -Sum of mean monthly temperatures divided by 12. 7. Mean Annual Temperature Range –Difference between the highest and the lowest mean monthly temperatures in a year. ◦k=◦c+273 ◦F=(◦c×1.8)+32 derive the rest from the formulas. Rain gauge is the instrument used to measure the amount of rainfall in a day. It should be made of impermeable material which can’t absorb water. How It’s Used/Works It’s taken to an open space to prevent water from dropping into the funnel. Its sunk into the ground to prevent evaporation The funnel top is left 30cm above the ground to prevent splashes of water and run off. After 24 hours water is emptied into the measuring cylinder. The reading of the amount of rainfall is got from the measuring cylinder in millimetres. The figure represents the millimetres of water falling on each square millimetre of the ground. It could be used to measure snow fall by melting it before the readings are gotten. Calculating Rainfall 1. Monthly Rainfall Total –Sum of rainfall recorded in a month. 2. Annual Rainfall Total -Sum of monthly rainfall totals for 12 months. 3. Mean Monthly Rainfall -Sum of rainfall totals for a particular month over several years divided by the number of the years of observation. 4. Mean Annual Rainfall -Sum of mean monthly rainfall for 12 months of the year. Sunshine   Duration of sunshine is measured using Campbell stokes sunshine recorder. How It Works Spherical lens focuses light on sensitized paper. The paper burns when the sun is shining. The total hours of sunshine is got by adding all the burnt sections from calibrations on the side of sensitized paper. The sensitized paper is changed every day. Humidity Humidity is the condition of atmosphere with reference to its water content. It’s measured with hygrometer or psychrometer which consists of wet and dry bulb thermometers kept in Stevenson screen. Dry bulb thermometer is a thermometer covered with muslin bag immersed in water while dry bulb thermometer has no muslin. How It Works When air is dry there is a lot of evaporation from the muslin. Evaporation cools the bulb of thermometer resulting in a low temperature reading. When humidity is high there is little evaporation from the muslin. The wet bulb thermometer is cooled at a slower rate and both thermometers show almost the same temperature reading. The difference in readings between the two thermometers is used to determine relative humidity. Interpretation of Hygrometer Readings When the 2 readings are the same, relative humidity is 100% i.e. the air is saturated. If the difference is small, humidity is high. If the difference is big, humidity is very low. Calculating Humidity Absolute Humidity -Actual amount of water vapour a given volume of air can hold. It’s expressed in g/m3. Specific Humidity Mass of water vapour in a given mass of air. It’s expressed in g/km. Relative Humidity Ratio between the absolute humidity and the maximum amount of water the air can hold expressed in a percentage. R.H.=A.H/Maximum amount of water the air can hold at the same