Editing Lake Malawi (section)

==Geological history==
[[File:FlankMalawi.png|thumb|left|upright=1.75|[[Topographic profile]] of Lake Malawi's [[rift shoulder]]]]
[[File:Map of Great Rift Valley.svg|thumb|The [[East African Rift]] (red) with the [[Rift Valley lakes]], Malawi being in the south]]
Malawi is one of the major [[Rift Valley lakes]] and an [[ancient lake]]. The lake lies in a valley formed by the opening of the [[East African Rift]], where the [[African Plate|African tectonic plate]] is being split into two pieces. This is called a divergent plate tectonics boundary. Malawi has typically been estimated to be 1–2 million years old (mya),<ref>{{Cite journal | doi = 10.1371/journal.pone.0001979 | date=Apr 2008 |last1=Wilson |first1=Ab.|last2=Teugels |first2=Gg. |last3=Meyer |first3=A. | title = Marine Incursion: The Freshwater Herring of Lake Tanganyika Are the Product of a Marine Invasion into West Africa| volume = 3| issue = 4| pages = e1979| pmid = 18431469| pmc = 2292254| journal = PLOS ONE| bibcode=2008PLoSO...3.1979W| editor1-last = Moritz| editor1-first = Craig| doi-access=free }}</ref><ref name=Givnish1997>Givnish, T.J.; and K.J. Sytsma, editors (1997). Molecular Evolution and Adaptive Radiation, p. 598. {{ISBN|0-521-57329-7}}.</ref> but more recent evidence points to a considerably older lake with a basin that started to form about 8.6 mya and deep-water condition first appeared 4.5 mya.<ref name=Delvaux1995>Delvaux, D. (1995). Age of Lake Malawi (Nyasa) and water level fluctuations. Mus. roy. Afr. centr., Tervuren (Belg.), Dept. Geol. Min., Rapp. ann. 1993 & 1994: 99–108.</ref><ref name=Sturmbauer2001>Sturmbauer; Baric; Salzburger; Rüber; and Verheyen (2001). Lake Level Fluctuations Synchronize Genetic Divergences of Cichlid Fishes in African Lakes. Mol Biol Evol 18(2): 144–154. {{doi|10.1093/oxfordjournals.molbev.a003788}}</ref>

The water levels have varied dramatically over time, ranging from almost {{convert|600|m|ft|abbr=on}} below current level<ref name=Cohen2007>Cohen; Stone; Beuning; Park; Reinthal; Dettman; Scholz; Johnson; King; Talbot; Brown; and Ivory (2007). Ecological consequences of early Late Pleistocene megadroughts in tropical Africas. Proc Natl Acad Sci USA 104(42): 16422-16427. {{doi|10.1073/pnas.0703873104}}</ref> to {{convert|10-20|m|ft|abbr=on}} above.<ref name=Delvaux1995/> During periods the lake dried out almost completely, leaving only one or two relatively small, highly [[Hard water|alkaline]] and [[Salt lake|saline]] lakes in what currently are Malawi's deepest parts.<ref name=Delvaux1995/><ref name=Cohen2007/> A water chemistry resembling the current conditions only appeared about 60,000 years ago.<ref name=Cohen2007/> Major low-water periods are estimated to have occurred about 1.6 to 1.0–0.57 million years ago (where it might have dried out completely), 420,000 to 250,000–110,000 years ago,<ref name=Delvaux1995/> about 25,000 years ago and 18,000–10,700 years ago.<ref name=Sturmbauer2001/> During the peak of the low-water period between 1390 and 1860 [[AD]], it may have been {{convert|120-150|m|ft|abbr=on}} below current water levels.<ref name=Givnish1997/>