Lake Makgadikgadi

Coordinates: 20°43′0″S 24°57′3″E / 20.71667°S 24.95083°E / -20.71667; 24.95083
Source: Wikipedia, the free encyclopedia.
Not to be confused with the extant Lake Magadi in Kenya's African Rift valley.
Not to be confused with the extant Lake Magadi in the Ngorogoro crater of Tanzania.
Lake Makgadikgadi
The extent of the former Lake Makgadikgadi.
Location of Lake Makgadikgadi in Botswana.
Location of Lake Makgadikgadi in Botswana.
Lake Makgadikgadi
Location of Lake Makgadikgadi in Botswana.
Location of Lake Makgadikgadi in Botswana.
Lake Makgadikgadi
LocationKalahari Desert in Botswana
Coordinates20°43′0″S 24°57′3″E / 20.71667°S 24.95083°E / -20.71667; 24.95083
Basin countriesBotswana
Average depth30 metres (98 ft)
greater flamingos

Lake Makgadikgadi (

paleolake that existed in what is now the Kalahari Desert in Botswana from 2,000,000 years BP to 10,000 years BP. It may have once covered an area of from 80,000 to 275,000 km2 (30,888 to 106,178 sq mi) and was 30 metres (98 ft) deep.[1] The Okavango, Upper Zambezi, and Cuando rivers once all emptied into the lake. Its remains are seen in the Makgadikgadi salt pans, one of the largest salt pans
in the world.

Homo sapiens, where humans first evolved as a distinct species about 200,000 years ago, before expanding to other parts of Africa about 70,000 years later.[2][3]

Origin and history

Approximately 3 million years ago, strong easterly winds formed long dunes, which ran from east to west across the middle of the Kalahari Desert. During wetter times, these dunes channeled the great rivers of the area, the

Chobe, and Upper Zambezi, southeastward to join with the Limpopo River and drain into the Indian Ocean.[4]

Northern Botswana has a series of deep, underlying

Chobe River, mark the line of these faults today.[5]

Approximately 2 million years ago, the fault known as the Ovamboland-Kalahari-Zimbabwe axis (which runs from NE to SW from

Kalahari desert) moved in an epeirogenic flexure
, and cut off the drainage route into the Limpopo. The blocked outflow allowed for the creation of Lake Makgadikgadi.

The great Magwikwe Sand Ridge between Savuti and North Gate probably defined one of its northwestern shorelines. Another is thought to have been the less obvious Gidikwe Sand Ridge lying just to the west of the western border of the present Makgadikgadi National Park.

Wave-washed features can be found on several of the Kalahari's higher places in this region. The eastern side of the Ghoha Hills, north of Savuti, is a particularly clear example of this. Round, water-eroded pebbles can also be found.

As the millennia passed, the lake filled to capacity. It began to overflow about 20,000 years ago, taking the lowest point in the

Victoria Falls. With the water now able to flow out of the basin, Lake Makgadikgadi drained partially and its average level decreased.[6]

A drier climatic period followed, which increased evaporation and decreased the flow of the rivers that fed the lake. By about 10,000 years ago the drying of Lake Makgadikgadi was in an advanced stage. Sediment and debris from the Okavango River and windblown sand were gradually filling the lake.[5]

The Gumare fault formed and lowered the land. As a result, the water of the Okavango River spread out over a much larger area of land than it previously had, forming the now characteristic fan-shaped inland delta of the Okavango, which further reduced the water that flowed into Lake Makgadikgadi and hastened its demise.

Human origin theory

In October 2019, a team led by

kya). They concluded this was in an area south of the Zambezi River, encompassing parts of what’s now known as Botswana, Namibia, and Zimbabwe. This corresponds to the shores of the ancient Lake Makgadikgadi.[7]

The conclusion is disputed by Chris Stringer, head of human origins at the Natural History Museum in London, and Sarah Tishkoff, a geneticist at the University of Pennsylvania.[8][3]

Excavations of early Homo sapiens activities have been found at Ga-Mohana Hill in Northern Cape dated to 105,000 years ago (105

kya).[9]

Ecology

Lake Makgadikgadi is theorised to have been the birthplace of the vast number of

cichlids that once swam the Congo, Zambezi, Okavango and Limpopo rivers—as many as 100 to 400 new species, of which approximately 25 survive today.[10]
The lake's sheer size may have provided the ancestors of these fish with an extremely wide range of new ecological niches to exploit and thus could have served as the stimulus for the evolution of the new species, which they may have done in record time before the lake drained completely. The theory further says that the new species, after having evolved within the confines of the lake, could have escaped with the lakewater as it drained, and populated the rivers of the region to evolve into the cichlids that exist today.

In current times this land is desiccated most of the year and is a seasonal wetland in the rainy summer months.[11]

Legacy

Today the only remains of Lake Makgadikgadi are the

Nwetwe Pan
.

The

evaporated and transpired
.

The other south draining rivers that once fed the lake have now all been captured by the Zambezi.

References

  1. ^ "Makgadikgadi Salt Pans". earthobservatory.nasa.gov. 2018-07-06. Retrieved 2018-08-16.
  2. ^ Michael Irving (October 28, 2019). "DNA study claims human "homeland" was a southern African wetland". New Atlas. Retrieved October 28, 2019.
  3. ^
    S2CID 204946938
    .
  4. S2CID 16200741
    .
  5. ^ a b c "Geological history - Botswana Travel Guide". www.botswana-travel-guide.com. Retrieved 2018-08-15.
  6. ^ "Geological history - Botswana Travel Guide". www.botswana-travel-guide.com. Retrieved 2021-04-13.
  7. ^ Irving, Michael (2019-10-28). "DNA study claims human "homeland" was a southern African wetland". New Atlas. Retrieved 2021-03-01.
  8. ISSN 0261-3077
    . Retrieved 2019-10-29.
  9. S2CID 232483324
    .
  10. ^ Owen, James (May 4, 2005). "Lost African Lake Spawned Fish Diversity 'Beyond Belief'". National Geographic News. Archived from the original on May 14, 2005. Alt URL
  11. ^ Hogan, C. Michael (2008). Burnham, A. (ed.). "Makgadikgadi". The Megalithic Portal.

External links

Wikimedia Commons has media related to Lake Makgadikgadi.
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