Meteor impact sites

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Tswaing Crater outside Pretoria

As meteorite impacts go, few come larger and more devastating than a 10km chunk of space rock screaming towards Earth around 2-billion years ago.

This meteorite, larger than Table Mountain, slammed into the Earth with unimaginable force, literally shaking the planet. Its impact site was where we now find the peaceful little town of Vredefort in the northern Free State, close to better-known Parys beside the Vaal River.

At 'Ground Zero', the rock instantly became molten, exploding into the atmosphere along with earth and superheated gases, and raining down for hundreds of kilometres.

The dust that the impact threw up would have blanketed the Earth for millennia, causing dramatic global cooling and a crater about 300km across. In 2005 the Vredefort Dome became South Africa's 7th World Heritage Site. Describing its global significance, the UNESCO World Heritage Site listing says, 'It is the site of the world’s greatest single, known energy release event.'

Meteors have always been agents of violent change on the planet. Some speculate this meteor strike may have introduced that terribly corrosive gas we so enjoy today - oxygen.

The most visible of the 4 major meteorite impact sites in South Africa lies 40km north of Pretoria: the Tswaing Crater.

This was caused by a relatively recent event - a much smaller meteor - 30-50 metres in diameter - hitting Earth less than 250 000 years ago. Tswaing is also becoming famous for birding opportunities, lying as it does in dense bushveld, with a wetland nearby. Meaning 'place of salts' in the local Setswana tongue, Tswaing was once rich in salt and soda ash.

Yet another meteor hit a spot near the town of Graaff-Reinet in the Great Karoo nearly 2-million years ago. The impact left a crater 460 metres in diameter and more than 200 metres deep.

Another impact crater, this time in the Kalahari Desert near the village of Morokweng, spans 160km in diameter, which makes it also 1 of the largest in the world.