Lake Suguta is a former lake in East Africa. It formed in the Suguta Valley, which is part of the East African Rift, south of Lake Turkana during the Holocene African humid period. The lake existed a number of times during history, most recently during the early and middle Holocene when a stronger monsoon caused increased precipitation in the basin of the lake. The lake then reached a top elevation of 577 metres (1,893 ft) above sea level, when it overflowed into the Kerio River and then into Lake Turkana. The lake possibly ultimately drained into the Nile. Between 8,000 and 5,000 years ago the lake progressively dried up; today only the small Lake Logipi occupies the area.
Geography and geology Lake Suguta lies in the Kenya Rift, which is part of the East African Rift. Starting with the Miocene, plate tectonics resulted in the pulling apart of the crust and the formation of the rift valley along with volcanoes; these include The Barrier volcano which starting from 1.3 million years ago and definitively from 0.2-0.1 million years ago separates Lake Suguta from Lake Turkana farther north. Volcanic activity in the region occurred as recently as 200 years ago. The Suguta valley today is about 20 kilometres (12 mi) wide and 80 kilometres (50 mi) long, dropping down northwards to a lowermost elevation of 275 metres (902 ft) above sea level. It is relatively remote.
The lake
At highstand, Lake Suguta had a roughly rectangular shape with the long side trending north-northeast from Emuruangogolak volcano in the south to The Barrier in the north, and between the Loriu Plateau west and Tirr Tirr Plateau east of the valley. The lake covered a total area of 2,150 square kilometres (830 sq mi) and was about 300 metres (980 ft) deep. The Pliocene-Pleistocene Namarunu volcano formed a peninsula on the western coast, while the Kamuge River valley at the southwestern end of the lake was occupied by a bay. A cinder cone formed an island at the northern end of Lake Suguta and was reached by humans, judging by the presence of obsidian artifacts; traces of human activity have also been encountered Wavecut terraces are found at the former shorelines of Lake Suguta, particularly at elevations of 577 metres (1,893 ft) which is where the main shoreline of Lake Suguta and also its highstand is located. Volcanism occurred in the area of Lake Suguta when it existed, resulting in the formation of pillow lavas and phreatomagmatic activity, lava flows of Emuruangogolak volcano reached the lake on its southern margin 11,000 - 9,000 years before present, and a layer of tephra was deposited in parts of the lake 8,770 years before present. A number of cinder cones have been modified by Lake Suguta, and the increased availability of water allowed the onset of fumarolic activity at volcanoes today too dry to support fumaroles, such as on The Barrier where fumarole sinter was emplaced when Lake Suguta existed. Some shorelines have been offset by faults, and the entire lake basin is tectonically tilted eastward, resulting in a corresponding vertical offset of shorelines. The existence of the lake itself affected regional tectonics; its disappearance and resulting unloading of the crust resulted in isostatic rebound in the area.
Hydrology The lake had two inflows, the Suguta River to the south and the Baragoi River to the southeast. The Baragoi River drains the Tirr Tirr Plateau, while the 175 kilometres (109 mi) long Suguta River drains an area of 13,000 square kilometres (5,000 sq mi) of the Kenya Rift valley almost all the way from Paka volcano close to the equator. Lake Suguta at highstand had a volume of about 390 cubic kilometres (94 cu mi). Rivers transported sediments from the tectonically young terrain into the lake, forming deltas and resulting in high sedimentation rates close to the inlet of the Suguta River. During the highstand period of Lake Suguta, local precipitation was over 26% higher than today. Most likely, the strengthening of the monsoon - especially the Indian monsoon - drew humid air from the Congo into the region of Lake Suguta, increasing precipitation.
Overflow A presently 581 metres (1,906 ft) high sill separates the headwaters of the Kerio River (which drains to Lake Turkana) from these of the Kamuge River. Lake Suguta overflowed through this sill into Lake Turkana. Overflow over this sill controlled the lake levels at highstand; that it is higher than the highstand shoreline is most likely a consequence of the tectonic tilting of the basin. In addition, it is likely that during the highstand of Lake Suguta the Lake Baringo farther south overflowed into the Suguta River drainage basin, while Lake Turkana overflowed into the Nile. While this theory was at first viewed with scepticism, it is now likely that Lake Suguta was part of a large drainage system that formed a headwater for the White Nile along the Pibor River and Sobat River which connected Lake Turkana with the Nile.
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