Tswaing is an

impact crater An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters ...

in South Africa that is accompanied by a museum. It is situated 40 km to the north-west of

Pretoria Pretoria () is South Africa's administrative capital, serving as the seat of the Executive (government), executive branch of government, and as the host to all foreign embassies to South Africa. Pretoria straddles the Apies River and extends ...

. 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 sur ...

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

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

). 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 differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar System accreted to form primi ...

or stony meteorite some 30 to 50 m in diameter that was vapourised during the impact event.

Morokweng impact structure The Morokweng impact structure is an impact structure buried beneath the Kalahari Desert near the town of Morokweng in South Africa's North West province, close to the border with Botswana. Description The impact structure is at least about ...

, another crater of

origin, lies north-west of

Vryburg Vryburg () is a large agricultural town with a population of 48,400 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 the industrial ...

Etymology

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

Tswana Tswana may refer to: * Tswana people, the 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 * Bophuthatswana, the former ba ...

and the crater was also formerly known in English as ''Pretoria Saltpan crater'' and in Afrikaans as ''Soutpankrater''.

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 pa ...

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 (H2CO3), 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 g ...

and

sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...

and

Sotho Sotho may refer to: *Sotho people (or ''Basotho''), an African ethnic group principally resident in South Africa, Lesotho and southern Botswana * Sotho language (''Sesotho'' or ''Southern Sotho''), a Bantu language spoken in southern Africa, an off ...

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. De ...

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 a museum.

Status of protection

Tswaing is currently on the ''tentative list'' for consideration as a

World Heritage Site A World Heritage Site is a landmark or area with legal protection by an international convention administered by the United Nations Educational, Scientific and Cultural Organization (UNESCO). World Heritage Sites are designated by UNESCO for h ...

References

External links