This visit was co-organised by the CNISF and the Geological Society of South Africa.
Forty kilometers north of Pretoria - South Africa (about half an hour drive from Pretoria) is a ring of hills one kilometer in diameter and 100 meters high (the impact sent up 60 metres of earth to form the present-day crater rim).
These hills are the rest of an impact crater left by an asteroid which hit the area about 200 000 years ago. It is believed that the crater walls at Tswaing were originally about twice as high as they are today (see the Tswaing crater on google map).
The crater is called Tswaing in seTswana, the local language of the area, or Soutpan in Afrikaans. Both names mean Salt Pan and this derives from the lake of salty water located in the centre.
It is one of the best preserved meteorite craters in the world, and it's also fortunately very accessible - it is extremely easy to walk down into the crater.
Specialists think that the meteorite was the size of half a soccer field and that it hits the earth at 4000 kilometres per hour, with an impact the equivalent of about 100 atomic bombs of the type dropped on Hiroshima in 1945.
In a very friendly atmosphere, this visit has been co-organised on the 12/10/2002 by the South African section of the CNISF (Conseil National des Ingénieurs et Scientifiques de France), and the Geological Society of South Africa. It was hot and sunny, but the knowledge of the specialists was so interesting that everybody quickly forgot the weather detail.
Extract of the pamphlet given at the entrance:
"Storytellers say that there is a giant snake living in the Tswaing crater just below the surface of the lake. This creature is said to train sangomas (traditional healers) in their skills. The training is secret and when a person enters the crater either at noon or at night, it is believed that they get killed by the snake. There are rumours that there is a cave full of bones of the victims in the northern slope of the crater."
Fortunately, it was daylight ;-)!!!
It is interested to compare the small crater of Tswaing with the 2000 million year old impact at Vredefort (100 km south west of Johannesburg). There the structure created from the impact is 70 kilometers in diameter. This is apparently the oldest and largest impact structure known on Earth.