The stress distribution on the lithospheric plate due to excess magma pressure is obtained from an exact solution of the threedimensional theory of elasticity. Rift valleys are thought to have been developed either from the action of tensional forces in the crust or from the action of compressional forces. The block mountains, the high areas on either side of the rift valley note that the movement has been along the weak zones or fault line. The northernmost part of the rift forms the beqaa valley in lebanon. The rift valley and the block mountains are now formed. In kenya, the valley is deepest to the north of nairobi. Rift valleys differ from river or glacial valleys in that they are created by tectonic activity. Rift valleys differ from river valleys and glacial valleys in that they are created by tectonic activity and not the process of erosion.
A rift valley is the long, narrow, flatbottomed trough of land created when a block of earths lithospheric crust drops into the space thats left when two divergent tectonic. Lake water management in three ethiopian rift valley watersheds by katie graichen introduction across geographic and temporal scales, humans are drawn to water for both the concrete and intangible resources it provides. The most extensive rift valley is located along the crest of the midocean ridge system and is the result of sea floor spreading. Divergence can also cause earthquakes and if it occurs near the continental crust, a rift valley will be created through faulting. Pdf the stress distribution on the lithospheric plate due to excess magma pressure is obtained from an exact solution of the.
The analysis indicates that rift valley formation and associated structural and geophysical characteristics can be suitably explained by dikelike intrusions of magma or igneous mush into the lithospheric plate. African rift tectonics and sedimentation, an introduction h. Examples of this type of rift include the midatlantic ridge and the east pacific rise many existing continental rift valleys are the result of a failed arm of a triple junction, although there are two, the east african rift and the baikal. A rift valley is a huge fracture on continental and oceanic plates which widens gradually over extensive periods of times.
The great rift valley is comprised of the great rift, jordan rift, red sea rift, east african rift, gregory rift and the western rift. The northwardmigrating spreading center pushed cimmeria in front of it, away from gondwana, replacing the old paleotethys ocean with a neotethys ocean. As the crust pulled apart, a rift valley formed and magma flowed up from. Rift valley fever an overview sciencedirect topics. Such a fault is a fracture in the terrestrial surface in which the rock material on the upper side of the fault plane has been displaced downward relative to the rock. The rift valleys are a system of normal faults bordering a 4060 km wide trough. The hypotheses regarding the origin of the rift valleys are generally grouped in two categories. Block mountains are formed c the middle block stays in the place and a rift valley form. The rift evolved into a spread center, separating the coastal fragment known as cimmeria. Farther south, the valley is the home of the jordan river which continues south through the jordan valley into the dead. Rift valley fever rvf is an acute, fever causing viral disease most commonly observed in domesticated animals such as cattle, buffalo, sheep, goats, and camels, with the ability to. Geology, geochemistry, and stratigraphy of the lemudongo formation, kenya rift valley article pdf available january 2007 with 650 reads how we measure reads. Rift valleys are found both on land and at the bottom of the ocean, where they are created by the process of seafloor spreading. Lake classification of lakes types of lakes pmf ias.
This small rift valley has a typical formationlong, narrow. Hence the lakes formed along rift valleys are also deep, narrow and very long. The ethiopian rift valley is created by volcanic and faulting activities that formed volcanotectonic depressions in the floor of the rift, which later becomes lakes 1. The great rift valley is a geographical feature running north to south for around 6,400 kilometres from northern syria to central mozambique in east africa. Rifting is the process in which continental crust is extended and thinned, forming extensional sedimentary basins andor mafic dykeswarms. Fold mountains and rift valleys flashcards quizlet. The rift extends from south in mozambique all the way up north in jordan to the southwestern asia. All of the african great lakes were formed as the result of the rift, and most lie within its rift valley. The analysis indicates that rift valley formation and associated structural and. What was the formation process of the great rift valley. While the name continues in some usages, it is rarely used in geology as it is considered an imprecise merging of separate though related rift and fault systems.
The ethiopian sector of the east african rift system extends for more than km in a nesw to ns direction from the afar depression, at red seagulf of aden junction, southwards to the turkana depression. A rift valley is a lowland region formed by the interaction of earths tectonic plates. A rift valley is formed when two blocks of earth move apart letting the in between block slide downwards. A rift valley is formed on a divergent plate boundary, a. The great rift valley central bucks school district. East african rift valley powerpoint slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Pdf mechanistic interpretation of rift valley formation. Africas great rift valley, 2001, isbn 0810906023 tribesofthegreatriftvalley,2007,isbn9780810994119 east african rift valley lakes, 2006, oclc 76876862 photographic atlas of the midatlantic ridge rift valley,1977,isbn0387902473 riftvalleyfever. Nevertheless, the formation of rift valley in kenya is an. Rift valley has a long history of operating in subsaharan africa. Rift valley fever is an infectious disease primarily affecting ruminants but to which other species, including humans, are also susceptible. Progressive formation of a rift valley through extension of the lithosphere and continental crust by about 50 km.
A rift valley is a lowland region that forms where earths tectonic plates move apart, or rift. The great rift valley olduvai gorge, in tanzanias great rift valley, is one of the most important sites for the study of human evolution. Oberrheinische tiefebene, oberrheinisches tiefland or oberrheingraben, french. Mechanistic interpretation of rift valley formation science. Desta stated that, awassa lake receives its recharge from groundwater through precipitation 2325. Chapter 4 lake water management in three ethiopian rift. As it spreads apart, the land between two parallel fault lines has sunk. The great rift valley is a series of contiguous geographic trenches, approximately 6,000 kilometres 3,700 mi in total length, that runs from the beqaa valley in lebanon which is in asia to mozambique in southeast africa.
Midcontinent rift the midcontinent rift formed when north america began to pull apart about 1 billion years ago. Introduction to rift valleys excerpt from national geographic education. Rift valley, any elongated trough formed by the subsidence of a segment of the earths crust between dipslip, or normal, faults. Inevitably, this human dynamic impacts ecological factors such as water quality. The formation of rift valleys and their zigzag fault patterns.
With total area of 90 km2, it is the smallest lake in the rift valley system. From its inception, rift valley has focused on six objectives. The southern boundary may be traced at latitude 5n, south of the area where the rift is divided into two branches chamo basin to. A stress analysis of the model shows how the rift valley and its fault pattern are formed on two oppositely inclined boundaries in the stress field. Tectonics rift valley formation teaching resources. It is found in the central rift valley system with altitudes ranging from 16702000m a. Threats and opportunities to major rift valley lakes. A rift valley is formed on a divergent plate boundary, a crustal extension or. Faulting rift valley and block mountains askmisstan.
Rifts commence as intracratonic, downthrown blocks dominated by normal or obliqueextensional transtensional faults e. The upper rhine plain, rhine rift valley or upper rhine graben german. History of the development of the east african rift system. Eduard suess thoughts on the east african rift system encouraged john gregory to further explore the faulted basins of kenya in 1893, and subsequently expressing the term rift valley. A rift valley is a landform whose formation is triggered by a geologic rift or fault. What is the difference between delta estuary lagoon bay gulf straits peninsula duration. There is also an atlas maps skills homework activity included in the lesson and a separate rift valley homework answer sheet to help give feedback to the students. The main phenomenon is formation of domes related to plume e. A rift formed along the northeastern shelf of gondwana.
What was once thought to be one giant 6,000mile long rift is now known to be several smaller rifts joined together. The east african rift, is a divergent plate boundary where the east african plate is being separated into two separate plates. Benefits of the rift valley to people of east africa. Olduvai, also known as oldupai, was the site of a large lake 500,000 years ago. Rift valley fever virus rvfv, the cause of rift valley fever rvf, is a zoonosis endemic to africa and the arabian peninsula that now represents a looming health threat to europe, asia, and the new world 1,2. There is a clear age predisposition to clinical disease rendering lambs, goat kids, puppies, and kittens extremely susceptible, with mortality rates between 70% and 100%. When the plates are pulled apart, the centre block drops down to form a graben. Tectonics and volcanism of the southern kenya rift valley and its. A rift valley is a linear shaped lowland between several highlands or mountain ranges created by the action of a geologic rift or fault. The formation of a rift valley and its zigzag fault patterns is simulated by a model experiment. Chris carlson slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Areas with the most recent rvf outbreaks include somalia 20067, kenya 20067, tanzania 2007, sudan 20078, mayotte 20078, madagascar 2008, swaziland 2008. A rift valley can be defined as a valley that is created by the splitting of the earths crust. Its southern section straddles the border between france.
Bedrock geology of michigan university of michigan. Divergent boundary, the great rift valley african rift. Winters book describes the inter congolese dialogue icd, which was the programme. What is not likely to happen at a divergent boundary. Rift valley corporation about us corporate governance. To demonstrate the formation of block mountains and rift. Some of the groups individual businesses have been in operation since the early 20th century.
The country has a number of lakes and rivers with substantial quantity of fish stocks. Textbook horst and graben formation left compared with actual rift terrain upper right and topography lower right. How rift valleys are formed some interesting facts. The eastern rift valley which is more commonly referred to as the great rift valley is a zone of tectonic subsidence that extends the full length of the ears. Scientists sometimes argue whether both block mountains horsts and rift valleys grabens move, or if only one part moves. Notice how the width taken up by the trapezoidal areas undergoing normal faulting and horst and graben formation increases from top to bottom in the left panel. The great rift valley is filled with hot springs, geysers and has multiple earthquakes each year. Rift valley formation rift valleys are formed on divergent plate boundaries when the plates are moving apart, it leaves a long deep gorge with reasonably flat sides and a flat floor.
There are 10 major lakes with a total area of 7400 km2 and 7185 km of major rivers 2. Pdf geology, geochemistry, and stratigraphy of the. The atlantic ocean, for instance, is a result of a triple junction that started in what is now the gulf of guinea on the. If you continue browsing the site, you agree to the use of cookies on this website. The land on both sides of the rift valley remains in place. Since all of these are formed at divergent plate boundaries, the. Building sustainable, longterm businesses in agriculture and energy 2. Note that uprise and decompression of the underlying asthenosphere results in magma formation. T he african rift valley system is one of the tectonic features not only of kenya but also of africa that extends from mozambique in the south through eastern africa to jordan in southwestern asia. A rift valley is a linearshaped lowland between several highlands or mountain ranges created by the action of a geologic rift or fault. Download fulltext pdf mechanistic interpretation of rift valley formation article pdf available in science 1894205. The third, failed rift or aulacogen, may become a rift valley. Rift valley fever, enzootic hepatitis, slenkdalkoors afrik. Formation of east african rift valley kenya wildlife safaris.
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