Tswaing (

Tswana Tswana may refer to: * Tswana people, the Bantu languages, Bantu speaking people in Botswana, South Africa, Namibia, Zimbabwe, Zambia, and other Southern Africa regions * Tswana language, the language spoken by the (Ba)Tswana people * Tswanaland, ...

for "place of salt") is an

impact crater An impact crater is a depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...

enclosed by a 1,946 ha nature reserve, situated in northern

Gauteng Gauteng ( , ; Sotho-Tswana languages, Sotho-Tswana for 'place of gold'; or ) is one of the nine provinces of South Africa. Situated on the Highveld, Gauteng is the smallest province by land area in South Africa. Although Gauteng accounts f ...

province, South Africa. The crater and reserve are situated on a base of ancient granite of the

Bushveld Igneous Complex The Bushveld Igneous Complex (BIC) is the largest Layered intrusion, layered igneous intrusion within the Earth's Crust (geology), crust. It has been tilted and Erosion, eroded forming the outcrops around what appears to be the edge of a great Ba ...

, some 40 km to the

north-northwest The points of the compass are a set of horizontal, Radius, radially arrayed compass directions (or Azimuth#In navigation, azimuths) used in navigation and cartography. A ''compass rose'' is primarily composed of four cardinal directions—north, ...

Pretoria Pretoria ( ; ) is the Capital of South Africa, administrative capital of South Africa, serving as the seat of the Executive (government), executive branch of government, and as the host to all foreign embassies to the country. Pretoria strad ...

(just north of

Soshanguve Soshanguve is a township situated about 30 km north of Pretoria, Gauteng, South Africa, just east of Mabopane. The name Soshanguve is an acronym for Sotho, Shangaan, Nguni and Venda, thus showing the multi-ethnic composition of the populat ...

). This

astrobleme An impact structure is a generally circular or craterlike geologic structure of deformed bedrock or sediment produced by impact on a planetary surface, whatever the stage of erosion of the structure. In contrast, an impact crater is the surface ...

is 1.13 km in diameter and 100 m deep and its age is estimated to be 220,000 ± 52,000 years (

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

). The impactor is believed to have been a

chondrite A chondrite is a stony (non-metallic) meteorite that has not been modified by either melting or planetary differentiation, differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar Syste ...

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

origin, lies north-west of

Vryburg Vryburg () is a large agricultural town with a population of approximately 89,120 situated in the Dr Ruth Segomotsi Mompati District Municipality of the North West Province (South Africa), North West Province of South Africa. It is the seat and ...

. Since 1996 it falls under the auspices of Ditsong Museums of South Africa.

Etymology

The name ''Tswaing'' means "place of salt" in

and the crater was also formerly known in English as the ''Pretoria Saltpan crater'' and in Afrikaans as ''Soutpankrater'', due to the highly saline lake on the crater floor.

Palaeoclimatology

Lipid biomarkers and carbon and hydrogen isotopic ratios from the lake indicate the existence of regional humid climatic periods between 84,000 and 80,000 years BP and between 50,000 and 39,000 BP. In contrast, intervals of high aridity occurred around 76,000 BP, from 73,000 to 69,000 BP, from 55,000 to 51,000 BP, and from 31,400 to 12,600 BP. Since 84,000 BP, the vegetation of the region around the lake has been dominated by savanna-type plants.

History

Stone tools from the

Middle Stone Age The Middle Stone Age (or MSA) was a period of African prehistory between the Early Stone Age and the Late Stone Age. It is generally considered to have begun around 280,000 years ago and ended around 50–25,000 years ago. The beginnings of ...

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 A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group . ...

and

sodium chloride Sodium chloride , commonly known as Salt#Edible salt, edible salt, is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. It is transparent or translucent, brittle, hygroscopic, and occurs a ...

and Sotho people harvested the salt by filtering and

decoction Decoction is a method of extraction by boiling herbal or plant material (which may include stems, roots, bark and rhizomes) to dissolve the chemicals of the material. It is the most common preparation method in various herbal medicine systems. D ...

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 World Heritage Sites are landmarks and areas with legal protection under an treaty, international treaty administered by UNESCO for having cultural, historical, or scientific significance. The sites are judged to contain "cultural and natural ...

References

External links

Tswaing Meteorite Crater
* ttps://web.archive.org/web/20080803050908/http://www.tshwane.gov.za/tswaing.cfm City of Tswhane - Tswaing Meteorite Crater {{DEFAULTSORT:Tswaing Crater Impact craters of South Africa Pleistocene impact craters Natural history museums in South Africa Museums in Pretoria