FAULTING• A fault is a break, crack or afracture in the Earths crust• produced by vertical and lateralmovements within the earth’scrust.• Faulting is one of the internal landform building process whichshapes the earth’s surface.• It is caused by earth movements,which create forces of tension andcompression that are either lateralor vertical.• If forces of tension andcompression are created by earthmovements the rocks of the earthcrust may fracture or crack.• thus the faults are formed .• The line along which rocks havefractured is called a fault.
Types of Faults• Normal fault• Reverse fault• Tear/Shear fault• Thrust fault• Anticlinal fault
Formed when rocks are subjected totensional forces . Normal faults develops. One block of land slides downwards in relationto the other. These types of faults are common in the EastAfrican section of the Great Rift valley.Normal FaultDown throwupthrow
Reverse faults• These are also knownas thrust faults .• caused by the forcesof compression.• when the strata orlayers are compressedor pressed ,the rockswill crack and faultswill be formed.• One block of rocksmay override anotherto form a block .• mountain or a horst.• Such faults arecommon in westernUganda.• The Ruwenzorimountain is anexample of a blockmountain formed bythrust faultsDown throw Up throw
Tear faultsWhen lateralmovement is takingplace particularlyduring an earthquake,tear faults may occur.Tear faults are alsoknown as wrench ortransform faults. If atear fault occursacross the course of ariver, then the river’scourse may be slightlyoffset.
FEATURES FORMED(PRODUCED) AS A RESULT OFFAULTINGFaulting has produced avariety of physicalfeatures over thesurface of the earth.Among the mostremarkable features are; Block mountains Rift Valleys Tilt blocks Escarpments/Faultscarp
A BLOCK MOUNTAINA block mountain is alsoknown as a Horst. It is formedwhen the middle block whichis bounded by more or lessparallel faults is made to riseor is uplifted by thecompressional forces. Thebest example of a blockmountain in East Africa ismount. Ruwenzori ranges,also known as the mountainsof the moon. Others includeMathews ranges and NyiruNdoto in Northern Kenya.Ablockmountainisalsoknownasa Horst.It
Tilt BlocksTilt blocks are formedwhen one side of themiddle block isuplifted higher thanthe other side. Thetop of the middleblock will not be flatbut will be tilted. E.g.west Kenya tilt block,which rises to about1900 meters towardslake Victoria.
EscarpmentsEscarpments are steep cliff-like slopes. Escarpmentsare said to have been formed during the formation ofthe rift valleys.Some escarpments are steep and may extend severalhundreds of kilometers . When escarpments areeroded, they become fault scarps.Examples of such escarpments in East Africa include: Nandi(Kenya) Butiaba (Uganda) Elgeyo Marakwet (Kenya) Kikuyu (Kenya) Mau (Kenya) Lake Manyara (Tanzania) Nyando (Kenya) Keiyo (Kenya) Nyandarua or Aberdares (Kenya) Chuya (Tanzania.)
Problems faced by the people living inthe Rift valley areas of East AfricaHigh temperatures lead to shortage of water.Earthquakes (tremors) which destroy propertyLittle rainfall or drought in the Rain shadowareasPoor means of transport and communicationbecause of the steep escarpments
Importance of faulting• Faulting has resulted into the formation of high mountains in East Africa. For example the Ruwenzori inwestern Uganda, the southern highlands and the Usambara mountains in Tanzania and the Mathew rangesin Kenya. These are the most productive areas, where both cash crops and subsistence crops are grown.• These highlands receive abundant and reliable rainfall.• Rift valley lakes for example L. Tanganyika, lake Turkana, lake Naivasha and lake Baringo are fishing grounds.• Some of these lakes have fresh water which can be used for irrigation and also for domestic purposes andindustrial use.• L.Magadi contains vast deposits of soda ash, which is one of the most important minerals in Kenya.• Faulting presents an impressive scenery which can be used for tourism. For example L.Nakuru has millions ofcolorful flamingos and other birds.• Some highlands have been made into National parks and game reserves e.g. the slopes of the Nyandaruaand Ruwenzori mountains . These parks attract many tourists.• Faulting can also cause the formation of waterfalls such as the Karuma falls, Murchison falls.• Problems caused by faulting• Escarpments and mountains hinder transport development.• Rift valleys are very hot and only suitable for grazing because they are in the rain shadow unless irrigation ispracticed as with the case of mubuku.• There is severe soil erosion and mass wasting on the step slopes which result in the destruction of soilsurface, crops and at times peoples property. For example Ruwenzori mountains.• It is difficult to settle on the steep areas on the rift valley escarpments.
RIFT VALLEYSA rift valley is an elongated trough bound by two in-facing escarpments.Rift valleys are long, narrow depressions on the earthsurface bounded by more or less parallel faults. A riftvalley is also known as a graven.Rift valleys are thought to have been developed eitherfrom the action of tensional forces in the crust or fromthe action of compressional forces.The East Africa rift valley system extends southwardsfrom the Red sea. Through Ethiopia and East Africa toMalawi.The east Africa rift valley covers a distance ofapproximately 5,600km .it is divided into twobranches that is, the western rift valley and theeastern rift valley.The Western branch stretches from lake Albert inUganda to lake Malawi. The eastern branch stretchesfrom lake Turkana in northern Kenya to lake Malawi.The width of the rift valley varies from place to place.The average width is between 50km and 60km.On the floor of the rift valley there are a number of riftlakes and volcanic craters such as Longonot crater andMenengai craters.
Origin of the rift valleys• A number of theories have been put forward toexplain the origin of rift valleys. However, twohave remained popular thus, there the twotheories which attempt to explain the origin ofrift valleys. One relies on the forces of tensionand the other on the forces of compression. Boththeories depend on upward swells, along thesides of which faults develop.
Origin of the rift valleysTheory 1: Tensional forces Theory 2. Compressional forcesAfter subsidence a depression with steep fault scarp sides i.e. a rift valley is formed. It is trapped inposition by later pressure.Theory 1: Tensional forcesa) Tension forces act on thelayers of rockb) Gradually two parallel faults appearand the central block begins to subside(sink).c) Land in between sinks in forming a rift valley. Theland on either sides stays in place.a) Layers of rocks are subjected tocompressional forces.b) Faults develop and the outer blocks moveupwards (Reverse faults are formed).c) Central block stays in place and a rift valley isformed.
RIFT VALLEY LAKES• These have been formedon the floor of the riftvalley and they vary insize, depth and salinity.Examples of the saltylakes are Natron, andMagadi. The rift valleyhas several in land waterbasins which containlakes.Rift valley lakes of East Africai.e.• Kenya• Uganda• Tanzania include:• L. Turkana• L. Tanganyika• L. Baringo• L. Edward• L .Rukwa• L. Nakuru• L. George.• L. Natron• L .Elmentaita• L .Eyasi• L. Naivasha• L. Manyara.• L. Albert• L. Magadi
FAULTED AREAS IN EAST AFRICA• There are faulted areas in east Africa outsidethe rift valley such as:• Kavirondo rift at Kisumu.• Northern face of which is the Nandi scarp• Usambara mountains have fault scarps
Benefits of the Rift valley to the peopleof East Africa• The beautiful scenery attracts tourists• Lakes in the Rift valley provide fish. For example L . Tanganyika, L.Albert etc.• Rift valley lakes provide water for domestic and agricultural use• Lakes help in navigation (water transport).• Forests on the slopes are sources of timber• Gentle slopes are used for crop farming and settlement due tofertile soils• Rift valley lakes are used for mining for example soda ash from L.Magadi• Areas of little rainfall (rain shadow) provides pasture for grazing|• Study purposes or research• Wildlife conservation. For example game parks in rift valley areas.
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