Year inscribed: 2005
Location: Free State and North West
Type: Natural heritage
Around 2-billion years ago a massive meteorite, 10 kilometres in diameter, hit the earth about 100km southwest of Johannesburg, creating an enormous impact crater. What remains of this impact crater is now known as the Vredefort Dome and is located near to the small Free State town of Vredefort.
The meteorite, which was larger than Table Mountain, caused a thousand-megaton blast of energy. This massive impact would have vaporised about 70 cubic kilometres of rock. Furthermore, the impact's side effect may have increased the earth's oxygen levels to a degree that made the development of multicellular life possible.
The world has about 170 crater structures of possible impact origin with four being found in South Africa. The Vredefort Dome is among the top three in the world, and is the oldest and largest clearly visible meteorite impact site.
The original impact crater, now eroded away, was probably 250 to 300 kilometres in diameter. This makes it larger than the Sudbury impact structure in Canada which is about 200km in diameter.
At 2-billion years old, the Vredefort impact structure is far older than the Chixculub impact structure in Mexico which, with an age of 65-million years, is the site of the impact that is thought to have led to the extinction of the dinosaurs.
Vredefort's original impact scar measures 380km across and consists of three concentric circles of uplifted rock. They were created by the rebound of rock below the impact site when the asteroid hit. Most of these structures have eroded away and are no longer clearly visible.
The inner circle, measuring 180km, is still visible and can be seen in the beautiful range of hills near Parys and Vredefort. It is this area that was named a World Heritage site.
The Vredefort Dome site fulfils all the criteria set by UNESCO for a World Heritage site. It is of outstanding universal value from a scientific point of view, and is remarkable evidence of an important moment in the earth's geologic history. It was voted South Africa's seventh World Heritage site at UNESCO's 29th World Heritage Committee meeting in Durban in July 2005.
Another geological significance of the Vredefort Dome impact crater is that when the ateroid hit the earth, the gold-bearing rocks of the Witwatersrand, which were deposited some 800 million years prior to the Vredefort impact, were covered with impact debris that protected them from erosion over the subsequent two billion years. See South African Geology & Geological Tour Guide
South Africa does have another well known and accesssible impact structure -- the much smaller 220 000 year old Tswaing Meteorite Crater which is located just north of Tshwane in the Gauteng Province.
South Africa's seven World Heritage Sites are:
 Cradle of Humankind
Greater St Lucia Wetland Park
Robben Island
uKhahlamba Drakensberg Park
Mapungubwe Cultural Landscape
Cape Floral Region
Vredefort Dome
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