Meidob volcanic field
Meidob volcanic field | |
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Highest point | |
Coordinates | 15°19′N 26°28′E / 15.32°N 26.47°E[1] |
Geography | |
Meidob volcanic field is a Holocene volcanic field in Darfur, Sudan. It is one of several volcanic fields in Africa whose origin is explained by the activity of mantle plumes and their interaction with crustal structures. Meidob lies at the southern margin of the Sahara.
The volcanic field is formed by overlapping
Volcanic activity in Meidob began 6.8 million years ago and continued into the Holocene, with the most recent eruptions dated to 4,900 ± 520 years ago. There are no geothermal manifestations at Meidob, but legends of the local people imply that they witnessed volcanic eruptions in the field.
Name
The term "Meidob" is derived from a
Geography and geomorphology
The Meidob volcanic field lies in
Meidob is a
The lava flows are between several metres to several tens of metres thick and reach lengths of more than 20 kilometres (12 mi). The less eroded lava flows have surface features typical of
The field has about 700 vents
About thirty maars and craters are found in the field, including the Malha crater (15°8′N 26°10′E / 15.133°N 26.167°E).[1] Malha is a crater about 150 metres (490 ft) deep and c. 1,050 metres (3,440 ft) wide. It has been excavated into the basement rock beneath the volcanic field,[14] and is itself surrounded by a rim less than 30 metres (100 ft) high.[4]
Malha contains a salty lake in the middle and several springs[5] fed by an aquifer,[16] and in the northeast side of the Malha crater a lava flow of the Jebel Sowidor lava field has invaded the crater depression.[10] There are other deep and wide craters in the field besides Malha.[17]
Hydrology
The southwestern
Geology
Alternatively, an origin as an intracontinental triple junction has also been proposed[24] but it has been contested on because of a lack of evidence supporting it.[25] Other proposals include the presence of laccoliths.[22] Volcanism elsewhere in northeast Africa has also been attributed to the Red Sea Rift and the Afar hotspot.[26]
Local
Jebel Marra and Meidob lie on an uplifted basement
The Meidob volcanic field and Jebel Marra with their
Tectonic lineaments control both the position of vents and that of dry valleys in the field.[30][13] There are both northeast-southwest, east-west and northwest-southeast trends, in order of decreasing importance.[12] These lineaments have been active at different times, indicating changes in the regional tectonic stress field.[31]
Composition
The Meidob volcanic field has erupted
The total volume of erupted rocks is about 1,400–1,800 cubic kilometres (340–430 cu mi),
Basanite is a product of
Climate and vegetation
Average yearly temperatures at Malha range between 21–29 °C (70–84 °F).
The lava fields are mostly barren, with the vegetation of the Meidob volcanic field consisting of
Eruption history
The oldest volcanic rocks in the Meidob volcanic field have been dated by
The field has been active during the Holocene, with thermoluminescence and tephrochronology dating giving a series of eruptions at the following dates (years ago):
- 14,600 ± 6,600 to 12,200 ± 3,300
- 10,100 ± 1,400 at Malha crater[b]
- 8,000 ± 1,600 to 7,200 ± 720
- 6,170 ± 1,450
- possibly 5,070 and 5,020
- 4,900 ± 520[1][11]
One of these recent eruptions had an intensity similar to a Plinian eruption,[45] and a volcanic explosivity index of 4 has been assigned to some eruptions.[1]
There are no fumaroles in the field,[35] while hot springs may[46] or may not exist;[35] but legends of the Midob recall that many generations ago, fire erupted from the Malha crater, and that water levels within its lake underwent changes[47] accompanied by sounds. These legends may reflect recent volcanic activity.[4]
Non-volcanic history
Apart from volcanism, aeolian processes and water erosion were active in Meidob, producing widespread sedimentary covers especially at the margins of the field. A number of wadis extend radially away from the centre of the Meidob volcanic field and carry water during flash floods, transporting sediment and floating pumice. Winds transport sediments onto old lava flows and volcanic landforms,[12] but owing to its youth many landforms of the Midob volcanic field are little eroded.[41]
During the early and middle Holocene a number of craters contained lakes;
Human use
The Meidob volcanic field was likely used as a source of obsidian,[41] and the Fur people obtained salt from the Malha crater.[53] This crater is an oasis[8] and was also a source of water for the Midob people.[4]
Notes
- ^ Or lava domes.[13]
- ^ However, a lava flow that enters this crater has yielded dates older than this.[44]
References
- ^ a b c d e f "Meidob Volcanic Field". Global Volcanism Program. Smithsonian Institution.
- S2CID 193011518.
- S2CID 151515593.
- ^ JSTOR 1785658.
- ^ a b c Lampen 1928, p. 55.
- S2CID 129700410.
- ^ a b c d Franz et al. 1997, p. 266.
- ^ a b Mees et al. 1991, p. 228.
- ^ a b c d e f Franz et al. 1997, p. 264.
- ^ a b Mees et al. 1991, p. 229.
- ^ a b c d e f g h Franz et al. 1997, p. 270.
- ^ a b c d Franz et al. 1997, p. 269.
- ^ a b c d Franz et al. 1994, p. 619.
- ^ a b c d Franz et al. 1997, p. 272.
- ^ Franz et al. 1997, p. 271.
- ^ a b Pachur & Altmann 2006, p. 266.
- ^ Franz et al. 1997, p. 274.
- ^ Pachur & Altmann 2006, p. 276.
- ^ Pachur & Altmann 2006, p. 277.
- ^ Pachur & Altmann 2006, p. 259.
- ^ Pachur & Altmann 2006, p. 283.
- ^ a b c Franz et al. 1994, p. 614.
- ^ Franz 1999, p. 28.
- ^ Franz 1999, p. 30.
- ^ Franz 1999, p. 43.
- ^ Lucassen et al. 2013, p. 183.
- ^ a b Franz et al. 1997, pp. 265–267.
- ^ a b Mees et al. 1991, p. 230.
- ^ Franz et al. 1994, p. 618.
- ^ Franz et al. 1997, p. 267.
- ^ Franz et al. 1997, p. 289.
- ^ Franz 1999, p. 34.
- ^ Franz 1999, p. 31.
- ^ a b Lucassen et al. 2013, p. 189.
- ^ a b c d Franz et al. 1997, p. 288.
- ^ Franz et al. 1997, p. 287.
- ^ a b Franz 1999, p. 42.
- ^ a b Mees et al. 1991, p. 231.
- ^ Mees et al. 1991, p. 249.
- ISBN 9783319898391.
- ^ a b c Pachur & Altmann 2006, p. 268.
- ^ Pachur & Altmann 2006, p. 272.
- ^ Franz 1999, p. 29.
- ^ Franz et al. 1997, p. 273.
- ^ Franz et al. 1997, p. 279.
- S2CID 53635777.
- ^ Lampen 1928, p. 57.
- ^ Pachur & Altmann 2006, p. 271.
- ^ Pachur & Altmann 2006, p. 465.
- ^ Pachur & Altmann 2006, p. 291.
- ISBN 9783527609789.
- ^ Mees, Florias; Richardson, Nigel (1994). "Holocene Sediments of the Crater Lake at Malha, Northwestern Sudan". Special Publications of SEPM: 135.
- JSTOR 40341621.
Sources
- Franz, G (3 May 1999). "Plume related alkaline magmatism in central Africa—the Meidob Hills (W Sudan)". Chemical Geology. 157 (1–2): 27–47. ISSN 0009-2541.
- Franz, Gerhard; Breitkreuz, Christoph; Coyle, David A.; El Hur, Bushra; Heinrich, Wilhelm; Paulick, Holger; Pudlo, Dieter; Smith, Robyn; Steiner, Gesine (August 1997). "The alkaline Meidob volcanic field (Late Cenozoic, northwest Sudan)". Journal of African Earth Sciences. 25 (2): 263–291. ISSN 1464-343X.
- Franz, G.; Pudlo, D.; Urlacher, G.; Haussmann, U.; Boven, A.; Wemmer, K. (1 October 1994). "The Darfur Dome, western Sudan: the product of a subcontinental mantle plume". Geologische Rundschau. 83 (3): 614–623. S2CID 198144219.
- Lampen, E. (1928). "A Short Account of Meidob". Sudan Notes and Records. 11: 55–67. JSTOR 41715948.
- Lucassen, Friedrich; Pudlo, Dieter; Franz, Gerhard; Romer, RolfL.; Dulski, Peter (1 January 2013). "Cenozoic intra-plate magmatism in the Darfur volcanic province: mantle source, phonolite-trachyte genesis and relation to other volcanic provinces in NE Africa". International Journal of Earth Sciences. 102 (1): 183–205. S2CID 128737594.
- Mees, Florias; Verschuren, Dirk; Nijs, Roger; Dumont, Henri (1 January 1991). "Holocene evolution of the crater lake at Malha, Northwest Sudan". Journal of Paleolimnology. 5 (3): 227–253. S2CID 129729861.
- Pachur, Hans-Joachim; Altmann, Norbert (2006). Die Ostsahara im Spätquartär (in German). SpringerLink. ISBN 978-3-540-47625-2.