Bayuda volcanic field

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]

Lava and scoria from Bayuda

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]

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]