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Great Rift Valley

Great Rift Valley

Overview


The Great Rift Valley is a name given in the late 19th century by British explorer John Walter Gregory
John Walter Gregory
John Walter Gregory, FRS, was a British geologist and explorer, known principally for his work on glacial geology and on the geography and geology of Australia and East Africa.-Early life:...

 to the continuous geographic trench, approximately 6000 kilometres (3,728.2 mi) in length, that runs from northern Syria
Syria
Syria , officially the Syrian Arab Republic , is a country in Western Asia, bordering Lebanon and the Mediterranean Sea to the West, Turkey to the north, Iraq to the east, Jordan to the south, and Israel to the southwest....

 in Southwest Asia
Southwest Asia
Western Asia, West Asia, Southwest Asia or Southwestern Asia are terms that describe the westernmost portion of Asia. The terms are partly coterminous with the Middle East, which describes a geographical position in relation to Western Europe rather than its location within Asia...

 to central Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...

 in South East Africa. The name continues in some usages, although it is today considered geologically imprecise as it combines features that are today regarded as separate, although related, rift
Rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....

 and fault systems. Today, the term is most often used to refer to the valley of the East African Rift
East African Rift
The East African Rift is an active continental rift zone in eastern Africa that appears to be a developing divergent tectonic plate boundary. It is part of the larger Great Rift Valley. The rift is a narrow zone in which the African Plate is in the process of splitting into two new tectonic plates...

, the divergent plate boundary which extends from the Afar Triple Junction
Afar Triple Junction
The Afar Triple Junction is a junction of three tectonic rifts centered in the Afar Depression, informally known as the Afar Triangle, of northeastern Africa. Here, the Red Sea Rift meets the Aden Ridge and the East African Rift...

 southward across eastern Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, and is in the process of splitting the African Plate
African Plate
The African Plate is a tectonic plate which includes the continent of Africa, as well as oceanic crust which lies between the continent and various surrounding ocean ridges.-Boundaries:...

 into two new separate plates.
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Encyclopedia


The Great Rift Valley is a name given in the late 19th century by British explorer John Walter Gregory
John Walter Gregory
John Walter Gregory, FRS, was a British geologist and explorer, known principally for his work on glacial geology and on the geography and geology of Australia and East Africa.-Early life:...

 to the continuous geographic trench, approximately 6000 kilometres (3,728.2 mi) in length, that runs from northern Syria
Syria
Syria , officially the Syrian Arab Republic , is a country in Western Asia, bordering Lebanon and the Mediterranean Sea to the West, Turkey to the north, Iraq to the east, Jordan to the south, and Israel to the southwest....

 in Southwest Asia
Southwest Asia
Western Asia, West Asia, Southwest Asia or Southwestern Asia are terms that describe the westernmost portion of Asia. The terms are partly coterminous with the Middle East, which describes a geographical position in relation to Western Europe rather than its location within Asia...

 to central Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...

 in South East Africa. The name continues in some usages, although it is today considered geologically imprecise as it combines features that are today regarded as separate, although related, rift
Rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....

 and fault systems. Today, the term is most often used to refer to the valley of the East African Rift
East African Rift
The East African Rift is an active continental rift zone in eastern Africa that appears to be a developing divergent tectonic plate boundary. It is part of the larger Great Rift Valley. The rift is a narrow zone in which the African Plate is in the process of splitting into two new tectonic plates...

, the divergent plate boundary which extends from the Afar Triple Junction
Afar Triple Junction
The Afar Triple Junction is a junction of three tectonic rifts centered in the Afar Depression, informally known as the Afar Triangle, of northeastern Africa. Here, the Red Sea Rift meets the Aden Ridge and the East African Rift...

 southward across eastern Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, and is in the process of splitting the African Plate
African Plate
The African Plate is a tectonic plate which includes the continent of Africa, as well as oceanic crust which lies between the continent and various surrounding ocean ridges.-Boundaries:...

 into two new separate plates. Geologists generally refer to these incipient plates as the Nubia
Nubia
Nubia is a region along the Nile river, which is located in northern Sudan and southern Egypt.There were a number of small Nubian kingdoms throughout the Middle Ages, the last of which collapsed in 1504, when Nubia became divided between Egypt and the Sennar sultanate resulting in the Arabization...

n Plate and the Somali Plate
Somali Plate
The Somali Plate or Somalian Plate is a tectonic plate that is being formed as the African Plate is splitting along the East African Rift. The part of the African Plate which lies on the other side of the rift is sometimes referred to as the Nubian Plate...

.

Geography



The Great Rift Valley as originally described extends from Lebanon
Lebanon
Lebanon , officially the Republic of LebanonRepublic of Lebanon is the most common term used by Lebanese government agencies. The term Lebanese Republic, a literal translation of the official Arabic and French names that is not used in today's world. Arabic is the most common language spoken among...

 in the north to Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...

 in the south, and constitutes one of two distinct physiographic provinces of the East African mountains
East African mountains
The East African mountains are a mountain region in East Africa, within Kenya, Uganda, Tanzania, Democratic Republic of Congo, Rwanda, and Burundi.-Location and description:...

.

Sinai peninsula



The northernmost part of the Rift, today called the Dead Sea Transform
Dead Sea Transform
The Dead Sea Transform fault system, also sometimes referred to as the Dead Sea Rift, is a geologic fault which runs from the Maras Triple Junction to the northern end of the Red Sea Rift...

 or Rift, forms the Beqaa Valley
Beqaa Valley
The Beqaa Valley is a fertile valley in east Lebanon. For the Romans, the Beqaa Valley was a major agricultural source, and today it remains Lebanon’s most important farming region...

 in Lebanon separating the Lebanon Mountains and Anti-Lebanon Mountains. Further south it is known as the Hula Valley separating the Galilee
Galilee
Galilee , is a large region in northern Israel which overlaps with much of the administrative North District of the country. Traditionally divided into Upper Galilee , Lower Galilee , and Western Galilee , extending from Dan to the north, at the base of Mount Hermon, along Mount Lebanon to the...

 mountains and the Golan Heights. The River Jordan begins here and flows southward through Lake Hula into the Sea of Galilee
Sea of Galilee
The Sea of Galilee, also Kinneret, Lake of Gennesaret, or Lake Tiberias , is the largest freshwater lake in Israel, and it is approximately in circumference, about long, and wide. The lake has a total area of , and a maximum depth of approximately 43 m...

 in Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...

, then continues south through the Jordan Rift Valley
Jordan Rift Valley
The Jordan Rift Valley is an elongated depression located in modern-day Israel, Jordan and the Palestinian territories. This geographic region includes the Jordan River, Jordan Valley, Hula Valley, Lake Tiberias and the Dead Sea, the lowest land elevation on Earth...

 into the Dead Sea
Dead Sea
The Dead Sea , also called the Salt Sea, is a salt lake bordering Jordan to the east and Israel and the West Bank to the west. Its surface and shores are below sea level, the lowest elevation on the Earth's surface. The Dead Sea is deep, the deepest hypersaline lake in the world...

 on the Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...

i-Jordan
Jordan
Jordan , officially the Hashemite Kingdom of Jordan , Al-Mamlaka al-Urduniyya al-Hashemiyya) is a kingdom on the East Bank of the River Jordan. The country borders Saudi Arabia to the east and south-east, Iraq to the north-east, Syria to the north and the West Bank and Israel to the west, sharing...

ian border. From the Dead Sea southwards, the Rift is occupied by the Wadi Arabah
Arabah
The Arabah , also known as Aravah, is a section of the Great Rift Valley running in a north-south orientation between the southern end of the Sea of Galilee down to the Dead Sea and continuing further south where it ends at the Gulf of Aqaba. It includes most of the border between Israel to the...

, then the Gulf of Aqaba
Gulf of Aqaba
The Gulf of Aqaba is a large gulf located at the northern tip of the Red Sea. In pre twentieth-century and modern sources it is often named the Gulf of Eilat, as Eilat is its predominant Israeli city ....

, and then the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...

. Off the southern tip of Sinai in the Red Sea, the Dead Sea Transform
Dead Sea Transform
The Dead Sea Transform fault system, also sometimes referred to as the Dead Sea Rift, is a geologic fault which runs from the Maras Triple Junction to the northern end of the Red Sea Rift...

 meets the Red Sea Rift
Red Sea Rift
The Red Sea Rift is a spreading center between two tectonic plates, the African Plate and the Arabian Plate. It extends down the length of the Red Sea, stretching from the southern end of the Dead Sea Transform to a triple junction with the Aden Ridge and the East African Rift in the Afar...

 which runs the length of the Red Sea. The Red Sea Rift comes ashore to meet the East African Rift
East African Rift
The East African Rift is an active continental rift zone in eastern Africa that appears to be a developing divergent tectonic plate boundary. It is part of the larger Great Rift Valley. The rift is a narrow zone in which the African Plate is in the process of splitting into two new tectonic plates...

 and the Aden Ridge
Aden Ridge
The Aden Ridge is a divergent tectonic plate boundary which runs offshore in the Gulf of Aden and Indian Ocean along the southeastern coastline of the Arabian Peninsula. It extends eastward from the Afar Triple Junction to a junction with the Owen Fracture Zone, and separates the Arabian Plate...

 in the Afar Depression
Afar Depression
The Afar Triangle is a geological depression that is caused by the Afar Triple Junction which is part of the Great Rift Valley. It overlaps Eritrea, Djibouti and the entire Afar Region of Ethiopia. The Afar Triangle includes the Danakil Depression and the lowest point in Africa, Lake Asal...

 of East Africa. The junction of these three rifts is called the Afar Triple Junction
Afar Triple Junction
The Afar Triple Junction is a junction of three tectonic rifts centered in the Afar Depression, informally known as the Afar Triangle, of northeastern Africa. Here, the Red Sea Rift meets the Aden Ridge and the East African Rift...

.

Africa


In eastern Africa, the valley divides into two, the Western Rift Valley and the Eastern Rift Valley.

The Western Rift, also called the Albertine Rift, is edged by some of the highest mountains in Africa, including the Virunga Mountains
Virunga Mountains
The Virunga Mountains are a chain of volcanoes in East Africa, along the northern border of Rwanda, the Democratic Republic of the Congo and Uganda. The mountain range is a branch of the Albertine Rift, a part of the Great Rift Valley. They are located between Lake Edward and Lake Kivu...

, Mitumba Mountains
Mitumba Mountains
The Mitumba Mountain range stretches along the Western Rift Valley in Burundi and Eastern Congo , west of lake Tanganyika. The two main peaks, Mount Kahuzi and Mount Biéga are extinct volcanoes.-References:...

, and Ruwenzori Range
Ruwenzori Range
The Rwenzori Mountains, previously called the Ruwenzori Range , and sometimes the Mountains of the Moon, is a mountain range of central Africa, often referred to as Mt...

. It contains the Rift Valley lakes
Rift Valley lakes
The Rift Valley lakes are a group of lakes in the Great Rift Valley formed by the East African Rift which runs through the whole eastern side of the African continent from north to south...

, which include some of the deepest lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

s in the world (up to 1,470 metres(4,800 ft) deep at Lake Tanganyika
Lake Tanganyika
Lake Tanganyika is an African Great Lake. It is estimated to be the second largest freshwater lake in the world by volume, and the second deepest, after Lake Baikal in Siberia; it is also the world's longest freshwater lake...

). Much of this area lies within the boundaries of national parks such as Virunga National Park
Virunga National Park
The Virunga National Park , formerly named Albert National Park, is a 7800 square km National Park that stretches from the Virunga Mountains in the South, to the Rwenzori Mountains in the North, in the eastern Democratic Republic of Congo, bordering Volcanoes National Park in Rwanda and Rwenzori...

 in the Democratic Republic of Congo, Rwenzori National Park and Queen Elizabeth National Park
Queen Elizabeth National Park
-Location:The national park is located in western Uganda, spanning the districts of Kasese, Kamwenge, Bushenyi and Rukungiri. Its location is approximately , by road, southwest of Kampala, Uganda's capital and largest city. The town of Kasese lies just outside the northeastern edge of the park,...

 in Uganda
Uganda
Uganda , officially the Republic of Uganda, is a landlocked country in East Africa. Uganda is also known as the "Pearl of Africa". It is bordered on the east by Kenya, on the north by South Sudan, on the west by the Democratic Republic of the Congo, on the southwest by Rwanda, and on the south by...

, and Volcanoes National Park
Volcanoes National Park
For the park in Hawaii, see Hawaii Volcanoes National Park.Volcanoes National Park lies in northwestern Rwanda and borders Virunga National Park in the Democratic Republic of Congo and Mgahinga Gorilla National Park in Uganda. The national park is known as a haven for the mountain gorilla...

 in Rwanda
Rwanda
Rwanda or , officially the Republic of Rwanda , is a country in central and eastern Africa with a population of approximately 11.4 million . Rwanda is located a few degrees south of the Equator, and is bordered by Uganda, Tanzania, Burundi and the Democratic Republic of the Congo...

. Lake Victoria
Lake Victoria
Lake Victoria is one of the African Great Lakes. The lake was named for Queen Victoria of the United Kingdom, by John Hanning Speke, the first European to discover this lake....

 is considered to be part of the rift valley system although it actually lies between the two branches. All of the African Great Lakes were formed as the result of the rift, and most lie within its rift valley.

In Kenya
Kenya
Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...

, the valley is deepest to the north of Nairobi
Nairobi
Nairobi is the capital and largest city of Kenya. The city and its surrounding area also forms the Nairobi County. The name "Nairobi" comes from the Maasai phrase Enkare Nyirobi, which translates to "the place of cool waters". However, it is popularly known as the "Green City in the Sun" and is...

. As the lakes in the Eastern Rift have no outlet to the sea and tend to be shallow, they have a high mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

 content as the evaporation of water leaves the salts behind. For example, Lake Magadi
Lake Magadi
Lake Magadi is the southernmost lake in the Kenya Rift Valley, lying in a catchment of faulted volcanic rocks, north of Tanzania's Lake Natron. During the dry season, it is 80% covered by soda and is well known for its wading birds, including flamingos....

 has high concentrations of soda (sodium carbonate
Sodium carbonate
Sodium carbonate , Na2CO3 is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. Sodium carbonate is domestically well-known for its everyday use as a water softener. It can be extracted from the...

) and Lake Elmenteita
Lake Elmenteita
Lake Elmenteita, also spelled Elementaita, is a soda lake, in the eastern limb of East Africa's Great Rift Valley, about 120 km northwest of Nairobi, Kenya.- Geography :...

, Lake Bogoria
Lake Bogoria
Lake Bogoria is a saline, alkaline lake that lies in a volcanic region in a half-graben basin south of Lake Baringo, Kenya, a little north of the equator. Lake Bogoria, like Lake Nakuru, Lake Elmenteita, and Lake Magadi further south in the Rift Valley, and Lake Logipi to the north, is home at...

, and Lake Nakuru
Lake Nakuru
Lake Nakuru is one of the Rift Valley soda lakes at an elevation of 1754 m above sea level. It lies to the south of Nakuru, in the rift valley of Kenya and is protected by Lake Nakuru National Park....

 are all strongly alkaline, while the freshwater springs supplying Lake Naivasha
Lake Naivasha
Lake Naivasha is a freshwater lake in Kenya, lying north west of Nairobi, outside the town of Naivasha. It is part of the Great Rift Valley. The name derives from the local Maasai name Nai'posha, meaning "rough water" because of the sudden storms which can arise...

 are essential to support its current biological variety.

Discoveries in human evolution



The Rift Valley in East Africa has been a rich source of fossils
that allow study of human evolution
Human evolution
Human evolution refers to the evolutionary history of the genus Homo, including the emergence of Homo sapiens as a distinct species and as a unique category of hominids and mammals...

.

Because the rapidly eroding highlands have filled the valley with sediments, a favorable environment for the preservation of remains has been created. The bones of several hominid
Hominidae
The Hominidae or include them .), as the term is used here, form a taxonomic family, including four extant genera: chimpanzees , gorillas , humans , and orangutans ....

 ancestors of modern humans have been found there, including those of "Lucy
Australopithecus afarensis
Australopithecus afarensis is an extinct hominid that lived between 3.9 and 2.9 million years ago. A. afarensis was slenderly built, like the younger Australopithecus africanus. It is thought that A...

", a partial, yet eye-opening australopithecine
Australopithecine
The term australopithecine refers generally to any species in the related genera Australopithecus or Paranthropus. These species occurred in the Plio-Pleistocene era, and were bipedal and dentally similar to humans, but with a brain size not much larger than modern apes, lacking the...

 skeleton, which was discovered by anthropologist Donald Johanson
Donald Johanson
Donald Carl Johanson is an American paleoanthropologist. Along with Maurice Taieb, and Yves Coppens he is known for the discovery of the skeleton of the female hominid australopithecine known as "Lucy", in the Afar Triangle region of Hadar, Ethiopia.-Early years:Johanson was born in Chicago,...

 dating back over 3 million years. Richard
Richard Leakey
Richard Erskine Frere Leakey is a politician, paleoanthropologist and conservationist. He is second of the three sons of the archaeologists Louis Leakey and Mary Leakey, and is the younger brother of Colin Leakey...

 and Mary Leakey
Mary Leakey
Mary Leakey was a British archaeologist and anthropologist, who discovered the first skull of a fossil ape on Rusinga Island and also a noted robust Australopithecine called Zinjanthropus at Olduvai. For much of her career she worked together with her husband, Louis Leakey, in Olduvai Gorge,...

 have also done significant work in this region.

More recently, two other hominid ancestors have been discovered there: a 10 million year-old ape called Chororapithecus abyssinicus
Chororapithecus abyssinicus
Chororapithecus abyssinicus was an ape that lived about during the Miocene Epoch. It is believed to be the earliest known species of gorilla...

, found in the Afar rift, in eastern Ethiopia, and the Nakalipithecus nakayamai
Nakalipithecus nakayamai
Nakalipithecus nakayamai is a prehistoric great ape species that lived in today's Kenya region early in the Late Miocene, 10 million years ago . It is the type species of the new genus Nakalipithecus...

, which is also 10 million years old.

See also

  • Great Rift: Africa's wild heart (TV series) A BBC
    BBC
    The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...

    /Animal Planet
    Animal Planet
    Animal Planet is an American cable tv specialty channel that launched on October 1, 1996. It is distributed by Discovery Communications. A high-definition simulcast of the channel launched on September 1, 2007.-History:...

     production
  • Main earthquakes
    • 1837 Galilee earthquake
      Galilee earthquake of 1837
      The Galilee earthquake of 1837, often called the Safed earthquake, was a devastating earthquake that shook the Galilee on January 1, 1837.-Impact:...

    • 2005 Lake Tanganyika earthquake
      2005 Lake Tanganyika earthquake
      The 2005 Lake Tanganyika earthquake occurred along the East African Great Rift Valley, and struck at 12:19:55 on 5 December 2005 with its focus approximately below the surface of Lake Tanganyika...

    • 2008 Lake Kivu earthquake
      2008 Lake Kivu earthquake
      The 2008 Lake Kivu earthquake shook several countries in Africa's Great Lakes region at 07:34:12 on February 3. It measured 5.9 on the moment magnitude scale according to the United States Geological Survey and lasted about 15 seconds...


Further reading

  • Africa's Great Rift Valley, 2001, ISBN 0810906023
  • Tribes of the Great Rift Valley, 2007, ISBN 9780810994119
  • East African Rift Valley lakes, 2006, OCLC 76876862
  • Photographic atlas of the Mid-Atlantic Ridge Rift Valley, 1977, ISBN 0387902473
  • Rift Valley fever : an emerging human and animal problem, 1982, ISBN 9241700637

External links