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28-686: The Wembere River originates in hilly country in central Tanzania at 6.0º south, and flows northwards through a branch of the Eastern Rift Valley . Its tributary the Nyahua River forms a seasonal floodplain 60 miles long and 1-5 km wide, covering 11,000 ha. After the Nyahua joins the Wembere from the northwest, the Wembere widens into a larger floodplain 105 km long and up to 20 km wide, and covering 140,000 ha. (4º12'-5º01' S/33º47'-34º11' E). Other tributaries are

56-450: A day failed. However, on the return journey, Thomson was gored by a buffalo and subsequently suffered from malaria and dysentery . He is credited with confirming Krapf's 1849 report of snow on Mt Kenya . He was prevented from making an attempt on the mountain by hostile Maasai. Nevertheless, he is commemorated on that mountain by Point Thomson (4,955 m) and Thomson's Flake. He recovered in time to give an account of his experiences at

84-607: A few kilometers in northern Tanzania, then splaying out in the North Tanzania Divergence. The Gregory Rift has shoulders rising over 3,000 metres (9,800 ft) above sea level, 1,000 metres (3,300 ft) above the inner part of the graben. The Tanzanian portion includes Mount Kilimanjaro , the highest mountain in Africa, and the huge caldera of Ngorongoro In the Crater highlands This portion also contains Ol Doinyo Lengai ,

112-617: A meeting in November 1884 of the Royal Geographical Society , which awarded him their Founder's Medal the following year. His book Through Masai Land followed in January 1885 and was a best seller. One of the first to read it was the young Henry Rider Haggard . His imagination fired by Thomson's expedition, Haggard promptly wrote a book of his own, King Solomon's Mines . Haggard also wrote other well received novels e.g. She , one of

140-668: A river in Tanzania is a stub . You can help Misplaced Pages by expanding it . Eastern Rift Valley The Gregory Rift ( Ufa la Gregori , in Swahili ) is the eastern branch of the East African Rift fracture system. The rift is being caused by the separation of the Somali Plate from the Nubian Plate , driven by a thermal plume . Although the term is sometimes used in the narrow sense of

168-583: A route from Dar es Salaam to Lake Nyasa and Lake Tanganyika . Johnston died during the trip and Thomson was left to take the leadership role for the expedition. Thomson successfully led the expedition over 5,000 kilometres (3,000 mi) in 14 months, collecting many specimens and recording many observations. Part of his crew included James Chuma , who also worked closely and assisted the Scottish explorer David Livingstone . In 1883, he embarked on another Royal Geographical Society expedition, this time to explore

196-542: A route from the eastern coast of Africa to the northern shores of Lake Victoria . British Empire traders wanted a route that would avoid potentially hostile Maasai and German traders who were competing in the area. The expedition set out a few months behind the rival German expedition of Gustav A. Fischer . Thomson's leadership was again a success, demonstrating the feasibility of the route and making many important biological, geological, and ethnographic observations, though Thomson's attempt to climb Mount Kilimanjaro in

224-595: A sequel which he wrote with Miss E. Harrison Smith as Ulu: an African Romance volume II . In 1885, Thomson was employed by the National African Company to forestall and hinder German influence in the vicinity of the Niger River , but he returned the following year to the UK to lecture, disillusioned that no further opportunities existed for large-scale exploration in the continent. He became discontented with his life in

252-534: A series succeeding King Solomon's Mines . The novel expands on further adventures of the main characters in King Solomon's Mines . When Thompson read She , he felt it did not represent the lands it was based on, and wrote a novel based on his experiences in the East African region, for example described in his book Through Masai Land . He called this novel Ulu: an African Romance . It was successful enough to demand

280-609: Is named in honour of the British geologist John Walter Gregory who explored the geology of the rift in 1892–93 and 1919. The Gregory Rift lies within the Mozambique belt , often considered to be the remains of an orogenic system similar to the Himalayas. This belt runs from Ethiopia through Kenya, Tanzania and Mozambique . The rift is widest at the northern end in the Afar region, narrowing to

308-546: The British government to claim the territory known as Zambezia (later Rhodesia, modern day Zimbabwe and Zambia ) as far north as the African Great Lakes . Though he made a sequence of important treaties on the trip, a smallpox epidemic in the intervening country stopped him from achieving the ultimate goal, which was to meet Alfred Sharpe at the court of Msiri , King of Katanga , and to assist Sharpe in incorporating

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336-609: The Kenyan Rift , the larger definition of the Gregory Rift is the set of faults and grabens extending southward from the Gulf of Aden through Ethiopia and Kenya into Northern Tanzania , passing over the local uplifts of the Ethiopian and Kenyan domes. Ancient fossils of early hominins , the ancestors of humans, have been found in the southern part of the Gregory Rift. The Gregory Rift

364-535: The Scramble for Africa . Thomson's gazelle and Thomson's Falls , Nyahururu , are named after him. Excelling as an explorer rather than an exact scientist, he avoided confrontations among his porters or with indigenous peoples, neither killing any native nor losing any of his men to violence. His motto is often quoted to be "He who goes gently, goes safely; he who goes safely, goes far." Born in Penpont , Dumfriesshire, he

392-703: The lithosphere may have thinned below the Gregory rift, although based on basalt geochemistry the lithosphere is at least 75 kilometres (47 mi) thick below the south of Kenya. The Gregory rift is oriented NS, and in the past the minimum horizontal tectonic stress direction was EW, the direction of extension. The alignment of rows of small vents , cones , domes and collapse pits in the Suswa , Silali and Kinangop Plateau regions support this theory. However, data from oil and gas exploration wells in Kenya, vents in volcanic shields to

420-434: The 1930s and collecting material that has led to the site being recognized as an important center of early hominin occupation. Volcanism and rifting started in Kenya in the northern region of Turkana between 40 and 35 million years ago and then spread north and south. To the south volcanism and rifting happened together, first in other parts of northern Kenya around 30 million years ago, then around 15 million years ago in

448-482: The Afar depression up to 100 metres (330 ft) thick. The first well-known European geologist to explore the region was Joseph Thomson , a member of an expedition in 1879–1880 sponsored by the Royal Geographical Society of Britain. From his observations he deduced the existence of a great fault. Thomson returned in 1883, traveling through the rift valley in Kenya from Mount Longonot to Lake Baringo . Describing

476-678: The Ethiopian flood basalts. Rifting in Ethiopia began about 18 million years ago in the southwest and 11 million years ago in northern parts of the Main Ethiopian Rift as the opening of the Gregory rift caused the Afar Triple Junction to form. Volcanism from the Middle Pleistocene onward formed a chain of volcanoes along the floor of the rift throughout its length, dividing it into separate valleys. There are some indications that

504-615: The UK and struggled to identify new opportunities for exploration. A modest expedition to the Atlas Mountains of Morocco was marred by trouble with porters and local political difficulties. He spent a month in 1889 travelling in central Europe with budding author J. M. Barrie . In 1890, Cecil Rhodes employed Thomson to explore north of the Zambezi , conclude treaties and gain mining concessions from tribal chiefs on behalf of his British South Africa Company , which had been chartered by

532-553: The Wamba, which joins from the northeast, the Mwaru, which joins from the east, and the Mapiringa, which joins from the west. The floodplain consists of flooded grasslands , inundated during the wet season and laced with drainage channels. Stands of the trees Vachellia seyal and Vachellia drepanolobium edge the seasonally-flooded portion of the plain. Above the floodplain, the eastern side of

560-466: The central Ethiopian plateau around 30 million years ago, long before rifting began. The first period of activity deposited flood basalts and rhyolites from 500 metres (1,600 ft) to 2,000 metres (6,600 ft) thick. Uplift of the Ethiopian plateau began around this time or soon after. Between 30 million and 10 million years ago synrift shield volcanoes deposited from 1,000 metres (3,300 ft) to 2,000 metres (6,600 ft) of additional material over

588-656: The central part of the Kenyan Rift , 12 million years ago in southern Kenya and 8 million years ago in northern Tanzania. When rifting reached the Tanzanian Craton , the rift split into the eastern Gregory Rift and the western Albertine Rift , which are separated by the 1,300 kilometres (810 mi) wide East African Plateau . Large shield volcanoes near the margins of the craton and in the adjacent Mozambique belt issued large volumes of basaltic to trachytic magmatism between five and one million years ago, with faulting around 1.2 million years ago. Volcanic activity started in

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616-458: The east of the rift at Huri Hills, Mount Marsabit and Nyambeni Hills and recent small cones at Suswa and east of the Silali caldera all indicate that the minimum horizontal stress direction has changed to NW-SE within the last half million years. Joseph Thomson (explorer) Joseph Thomson (14 February 1858 – 2 August 1895) was a British geologist and explorer who played an important part in

644-543: The mineral-rich country into Zambezia by treaty. Thomson's role was to have brought supplies of cloth, gunpowder and other gifts with which to impress Msiri. Without these, Sharpe was rebuffed, and a year later, the Stairs Expedition led by Captain William Stairs , believing itself to be in a race with another attempt by Thomson to reach Katanga, killed Msiri and took Katanga for King Leopold II of Belgium . Unknown to

672-690: The term "rift valley", which he defined as "a linear valley with parallel and almost vertical sides, which has fallen owing to a series of parallel faults". In 1913 the German geologist Hans Reck made the first European study of the strata in the Olduvai Gorge to the west of the Crater Highlands. He brought a large collection of mammalian fossils back to Berlin. In 1928 Louis Leakey , the anthropologist, visited Berlin, where he saw that some of Reck's materials were artifacts . Leakey began exploring Olduvai in

700-402: The valley around this lake he said: "Imagine if you can a trough or depression 3300 feet above sea level, and twenty miles broad, the mountains rising with very great abruptness on both sides to a height of 9000 feet". John Walter Gregory visited central Kenya in 1893 and again in 1919. His 1896 book The Great Rift Valley is considered a classic. Gregory was the first well-known European to use

728-529: The watershed is chiefly miombo woodland , and the western side, called the Wembere Steppe, is Acacia-Commiphora savanna . Below the floodplain the river turns northeast and empties into the south end of Lake Kitangiri . Lake Kitangiri empties into Lake Eyasi via the Sibiti River . 4°10′S 34°11′E  /  4.167°S 34.183°E  / -4.167; 34.183 This article related to

756-459: The world's only active carbonatite volcano. Lakes in the rift other than Lake Turkana are mostly small and shallow, some with fresh water but many being saline. The thickness of lake sediments is mostly unknown. In Lake Turkana they seem to be at most 4 kilometres (2.5 mi) thick, in the Baringo – Bogoria half-graben from 500 metres (1,600 ft) to 1,000 metres (3,300 ft) thick and in

784-483: Was apprenticed into his father's stone- masonry and quarrying business. He developed a keen amateur interest in geology and botany , which eventually led to his formal education at the University of Edinburgh , studying under Archibald Geikie and Thomas Henry Huxley . On graduating in 1878, he was appointed geologist and naturalist to Alexander Keith Johnston 's Royal Geographical Society expedition to establish

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