Английская Википедия:Bayuda volcanic field
Шаблон:Infobox mountain Bayuda volcanic field (also spelled Bayiuda[1]) is a volcanic field in Sudan, within the Bayuda Desert. It covers a surface of about Шаблон:Convert 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.
Geography and geomorphology
The volcanic field is located in the Bayuda Desert within the great bend of the Nile,[1] Шаблон:Convert north of Khartoum.Шаблон:Sfn It lies Шаблон:Convert away from Merowe; there are wells at Abu Khorit and SaniШаблон:Sfn north of the volcanic field.Шаблон:Sfn The field was discovered by aerial photography in 1920.Шаблон:Sfn Numerous Middle Stone Age and Paleolithic archeological sites are found in the field.[2]
Bayuda is an elongated volcanic field[1] with fresh volcanic featuresШаблон:Sfn extending over an area of Шаблон:Convert in northwesterly direction. Within this area, a number of volcanic vents within a narrow space have formed a continuous volcanic surface.Шаблон:Sfn Some individual lava fields cover over Шаблон:Convert of surface,Шаблон:Sfn but surfaces of about Шаблон:Convert are more typical.Шаблон:Sfn 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,Шаблон:Sfn generally corresponding to aa lava.Шаблон:Sfn Some flows reach lengths of Шаблон:ConvertШаблон:Sfn and thicknesses of Шаблон:Convert. The flows are often covered by ridges and hillocks.Шаблон:Sfn
Cinder cones make up the bulk of the field,[1] of which there are about one hundred.Шаблон:Sfn Usually the cones reach heights of over Шаблон:ConvertШаблон:Sfn and are formed by volcanic ash, lapilli, lava bombs and scoria.Шаблон:Sfn Many of these aside from pyroclastics also erupted lava flowsШаблон:Sfn which then broke the crater rims.[1] Explosion craters[1] and sporadic maars are also found,Шаблон:Sfn they are surrounded by tephra deposits which form low rims of pyroclastic materialШаблон:Sfn and which also cover neighbouring volcanoes.Шаблон:Sfn Individual vents form two separate alignments.Шаблон:Sfn
Hosh ed Salam ("dark enclosure"Шаблон:Sfn) crater is Шаблон:Convert deep and Шаблон:Convert 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.Шаблон:Sfn El Muweilih contains a salt lake after which it is named and which was used as a source of salt,Шаблон:Sfn while Jebel El Abour contains a secondary cone. The Sergein hills and Jebel Azrub are composite volcanoes.Шаблон:Sfn Angalafib, Goan and Jebel El Abour are also quite high.Шаблон:Sfn
Pumice blocks from the field were found in Wadi Abu Dom,Шаблон:Sfn and scoria downstream in the Nile.Шаблон:Sfn Tephra identified in deposits on Mograt Island in the Nile most likely comes from this volcanic field.[3] The volcanic field is a potential site for geothermal power development, with temperatures underground of about Шаблон:Convert.[4]
Geology
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 fieldШаблон:Sfn both in Darfur,Шаблон:Sfn and elsewhere in the form of small basaltic outcrops.Шаблон:Sfn Bayuda is a small volcanic field in comparison to other African volcanic fields.Шаблон:Sfn Volcanism at Bayuda may be associated with the Central African Shear ZoneШаблон:Sfn and of Precambrian faults,Шаблон:Sfn perhaps together with a mantle plume.Шаблон:Sfn 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.Шаблон:Sfn
The basement consists of granites of Precambrian and Paleozoic age[1] that belong to the Bayuda terrane,Шаблон:Sfn which together with gneisses form a gentle pediplain away from rougher landscape along the Nile.Шаблон:Sfn Later on during the Cretaceous the Nubian Formation was laid down and there are hints of a domal uplift in the Bayuda area,Шаблон:Sfn which probably predates the onset of volcanism and may have influenced the course of the Nile.Шаблон:Sfn The existence of such a dome has been questioned, however.Шаблон:Sfn
Composition
Bayuda has erupted basaltic rocks,Шаблон:Sfn with most collected rocks belonging to an alkali basalt suiteШаблон:Sfn although basanite, melabasanite, hawaiite and trachybasalt have been identified as well.Шаблон:SfnШаблон:Sfn Phenocrysts include clinopyroxene and olivine.Шаблон:Sfn Various xenoliths have been found, including garnet-containing clinopyroxenite, harzburgite, garnet hornblendite, amphibole-containing peridotite, olivine and spinel pyroxenite and websterite.Шаблон:Sfn
In general the composition resembles that of other Sudanese-Egyptian volcanoes,Шаблон:Sfn about two different magma families have been identified which originate from disparate mantle domains.Шаблон:Sfn Crystal fractionation of clinopyroxene, olivine and spinels took part in the formation of the magmas.Шаблон:Sfn The total volume of the volcanic rocks is about Шаблон:Convert,Шаблон:Sfn the rocks reach thicknesses of about Шаблон:Convert maximally.Шаблон:Sfn
Eruptive history
Volcanic activity has been dated to 1.7 - 0.9 million years ago,Шаблон:Sfn 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 volcanoesШаблон:Sfn such as Hosh ed Salam.Шаблон:Sfn The presence of maars and volcanoes with signs of phreatomagmatic activity may indicate activity during pluvials.Шаблон:Sfn 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.Шаблон:Sfn
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.Шаблон:Sfn Aside from this date, however, there is little information on the timing of recent volcanic activity in the Bayuda volcanic field.Шаблон:Sfn
References
Sources
- Шаблон:Cite journal
- Шаблон:Cite journal
- Шаблон:Cite journal
- Шаблон:Cite journal
- Шаблон:Cite book
- Шаблон:Cite journal
- Шаблон:Cite journal
- Шаблон:Cite book
- ↑ 1,0 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 Ошибка цитирования Неверный тег
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<ref>; для сносокKhadam2018не указан текст
