Tswaing (Tswana for "place of salt") is an impact crater enclosed by a 1,946 ha nature reserve, situated in northern Gauteng province, South Africa. The crater and reserve are situated on a base of ancient granite of the Bushveld Igneous Complex, some 40 km to the north-northwest of Pretoria (just north of Soshanguve). and its age is estimated to be 220,000 ± 52,000 years (Pleistocene). The impactor is believed to have been a chondrite or stony meteorite some 30 to 50 m in diameter that was vaporised during the impact event. Morokweng impact structure, another South African crater of chondrite origin, lies north-west of Vryburg. Since 1996 it falls under the auspices of Ditsong Museums of South Africa.

History

Stone tools from the Middle Stone Age show that the crater was regularly visited by people from as far back as 100,000 years ago in order to hunt and collect salt. Water in the crater comes from surface springs, ground water and rain water and is rich in dissolved carbonates and sodium chlorides. Tswana and Sotho people harvested the salt by filtering and decoction between 1200 and 1800. Between 1912 and 1956 brine was pumped from the floor of the crater by the company SA Alkali Ltd. in order to extract soda and salt.

A scientific dispute was ongoing regarding the origin of the crater between supporters of volcanic origin (Wagner, 1922) and those who believed it is an impact crater (Rohleder, 1933) until 1990, when examination of the core from a borehole proved that it is an impact crater.

Museum

The impact crater is accompanied by the Ditsong Tswaing Crater Museum.

Status of protection

Tswaing is currently on the tentative list for consideration as a World Heritage Site.

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File:Tswaing crater D3C1219-200530F026.jpg|Satellite photo of Tswaing crater in 1984

File:Nebograniet, nabyskoot in Soutpankraterwand, a.jpg|Nebo granite of the Bushveld Igneous Complex, from the crater wall

File:Tswaing crater-002.jpg|Memorial to Eugene Merle Shoemaker who showed that craters such as Tswaing are formed by impact

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See also

  • Impact event
  • List of impact craters in Africa

References

  • Tswaing Meteorite Crater
  • Hartebeesthoek Radio Astronomy Observatory writeup on the crater
  • City of Tswhane - Tswaing Meteorite Crater