Bayuda volcanic field | |
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Highest point | |
Elevation | 670 m (2,200 ft) [1] |
Coordinates | 18°20′N 32°45′E / 18.33°N 32.75°E [1] |
Geography | |
Geology | |
Last eruption | 1,102 ± 48 years ago |
Bayuda volcanic field (also spelled Bayiuda [1]) is a volcanic field in Sudan, within the Bayuda Desert. It covers a surface of about 11 by 48 kilometres (6.8 mi × 29.8 mi) and consists of a number of cinder cones as well as some maars and explosion craters. These vents have erupted 'A'ā lava flows.
The field rises above a Precambrian- Paleozoic basement that may be a domal uplift. There is little known about the occurrence of volcanic eruptions, but the last eruption has been dated to 1,102 ± 48 years before present.
The volcanic field is located in the Bayuda Desert within the great bend of the Nile, [1] 300 kilometres (190 mi) north of Khartoum. [2] It lies 80 kilometres (50 mi) away from Merowe; there are wells at Abu Khorit and Sani [3] north of the volcanic field. [4] The field was discovered by aerial photography in 1920. [3] Numerous Middle Stone Age and Paleolithic archeological sites are found in the field. [5]
Bayuda is an elongated volcanic field [1] with fresh volcanic features [3] extending over an area of 11 by 48 kilometres (6.8 mi × 29.8 mi) in northwesterly direction. Within this area, a number of volcanic vents within a narrow space have formed a continuous volcanic surface. [6] Some individual lava fields cover over 20 square kilometres (7.7 sq mi) of surface, [7] but surfaces of about 10 square kilometres (3.9 sq mi) are more typical. [8] There are usually only a few flows per vent, although they often have lobate structures. The surface of the lava flows has varying textures and often contains hills or ridges, [9] generally corresponding to aa lava. [10] Some flows reach lengths of 10 kilometres (6.2 mi) [11] and thicknesses of 30 metres (98 ft). The flows are often covered by ridges and hillocks. [12]
Cinder cones make up the bulk of the field, [1] of which there are about one hundred. [13] Usually the cones reach heights of over 400 metres (1,300 ft) [8] and are formed by volcanic ash, lapilli, lava bombs and scoria. [14] Many of these aside from pyroclastics also erupted lava flows [6] which then broke the crater rims. [1] Explosion craters [1] and sporadic maars are also found, [2] they are surrounded by tephra deposits which form low rims of pyroclastic material [15] and which also cover neighbouring volcanoes. [4] Individual vents form two separate alignments. [11]
Hosh ed Salam ("dark enclosure" [16]) crater is 500 metres (1,600 ft) deep and 1,300 metres (4,300 ft) wide, [1] other craters are Jebel Hebeish and El Muweilih which have formed shallow rises above the surrounding terrain and have cut into the basement rocks. [10] El Muweilih contains a salt lake after which it is named and which was used as a source of salt, [7] while Jebel El Abour contains a secondary cone. The Sergein hills and Jebel Azrub are composite volcanoes. [6] Angalafib, Goan and Jebel El Abour are also quite high. [7]
Pumice blocks from the field were found in Wadi Abu Dom, [3] and scoria downstream in the Nile. [16] Tephra identified in deposits on Mograt Island in the Nile most likely comes from this volcanic field. [17] The volcanic field is a potential site for geothermal power development, with temperatures underground of about 200 °C (392 °F). [18]
Volcanic activity has been taking place in Sudan since the Cretaceous, with most recent manifestations documented in the Bayuda volcanic field, Marra Mountains and Meidob volcanic field [3] both in Darfur, [19] and elsewhere in the form of small basaltic outcrops. [20] Bayuda is a small volcanic field in comparison to other African volcanic fields. [4] Volcanism at Bayuda may be associated with the Central African Shear Zone [21] and of Precambrian faults, [22] perhaps together with a mantle plume. [23] The area features four more volcanic fields, the "Northern Field" northeast, the Abu Rugheiwa field southeast and Shaq Umm Bosh and Muqqodom southwest of Bayuda. [24]
The basement consists of granites of Precambrian and Paleozoic age [1] that belong to the Bayuda terrane, [2] which together with gneisses form a gentle pediplain away from rougher landscape along the Nile. [25] Later on during the Cretaceous the Nubian Formation was laid down and there are hints of a domal uplift in the Bayuda area, [3] which probably predates the onset of volcanism and may have influenced the course of the Nile. [25] The existence of such a dome has been questioned, however. [26]
Bayuda has erupted basaltic rocks, [6] with most collected rocks belonging to an alkali basalt suite [27] although basanite, melabasanite, hawaiite and trachybasalt have been identified as well. [2] [28] Phenocrysts include clinopyroxene and olivine. [27] Various xenoliths have been found, including garnet-containing clinopyroxenite, harzburgite, garnet hornblendite, amphibole-containing peridotite, olivine and spinel pyroxenite and websterite. [29]
In general the composition resembles that of other Sudanese- Egyptian volcanoes, [2] about two different magma families have been identified which originate from disparate mantle domains. [11] Crystal fractionation of clinopyroxene, olivine and spinels took part in the formation of the magmas. [30] The total volume of the volcanic rocks is about 18 cubic kilometres (4.3 cu mi), [31] the rocks reach thicknesses of about 200 metres (660 ft) maximally. [4]
Volcanic activity has been dated to 1.7 - 0.9 million years ago, [32] but it continued after the end of the latest wet period 5,000 years ago [1] as indicated by the uneroded state of some of the volcanoes [4] such as Hosh ed Salam. [33] The presence of maars and volcanoes with signs of phreatomagmatic activity may indicate activity during pluvials. [34] Volcanism at Bayuda commenced with isolated volcanoes. After a while, new edifices were constructed atop the older ones, influencing the morphology of the new volcanoes. [31]
The most recent lava flow was dated to less than 1,100 years before present, [1] with radiocarbon dating producing an age of 1,102 ± 48 years before present. [8] Aside from this date, however, there is little information on the timing of recent volcanic activity in the Bayuda volcanic field. [34]