Tswaing Meteor Crater

Tswaing Crater seen from the rim. The rim is about 100 metres above the bottom of the crater. Inside is saline water, in the past soda and salt were extracted from the crater. The ruins of the factory and associated operations can be seen around the area. Tools from the middle stone age show that people have been coming to the crater for at least 100 000 years.

“The shockwave through the ground would have been equivalent to a major earthquake, but the air blast and associated impact debris would have done most of the damage. Loose rocks, debris from buildings, cars and even trees would have become lethal projectiles and within a radius of 50 km around the site all life would have been destroyed”. [1]

This is how McCarthy and Rubridge (2005) describe the impact of something the size of the object that hit the earth near Pretoria 200 000 years ago would be like. The devastation caused by something like that today would be catastrophic. Yet major impacts on earth are relatively common. Since 2000 there have been at least eight widely reported impact events. The most recent was Chelyabinsk meteor which exploded over Russia in February 2013. This was well documented and footage can be seen here.

Inside the crater the slopes are dominated by Vachellia robusta and Combretum trees. Creating a good habitat for birds and other animals that favour woodland environments.

From inside the crater one is struck by the roundness of the rim.

McCarthy and Rubridge Break down the estimates of how often impact events of different magnitudes take place. Every 100 million (10⁸) years an impact leading to global mass extinction occurs. Smaller events causing craters 20-50km in diameter occur once every 500 000 years and even smaller events, like the one that caused the Tswaing Crater occur as often as one to three times per hundred years.[2] These kind of numbers really bring ones tentative place on earth into perspective. The Hollywood version would have a hero going up into space and somehow stopping the massive body from colliding with the earth, but that is a fantasy. A meteor the size of the one that created the Vredefort Dome in South Africa would not be stopped and impact and extinction would be unavoidable.

A satellite image of Tswaing Crater. The urban sprawl is beginning to encroach on the crater.

But what will be will be and the event that happened 200 000 years ago left a remarkable crater and the surrounding environment has become Tswaing Meteor Crater Nature Reserve. The reserve is surrounded by urban sprawl, but is a refuge for some wildlife that would otherwise have nowhere else to go. It is also a good birding area, I have observed: Green-backed Herons, Magpie Shrikes, Temnick's Courser, Wattled Starling, African Hawk-Eagles, Red-billed Hornbills, Yellow-Billed Hornbills and African Grey Hornbills.

There are many Variable Skinks (Trachylepis varia) moving around in the leaf litter around the crater.

On a single small tree (Combretum molle), without looking too hard I found three different insects all apparently feeding on the new growth of the tree. 

Velvet Bush Willow (Combretum molle). On this small tree I found three different types of insects just by quickly scanning what was moving around. With a bit more effort I am sure I could have found more than three times that amount.

Fruit chafers (Pedinorrhina trivittata) clambering on a branch.

Another fruit chafer but a different species (Clinteroides permutans).

This Polyrhachis ant was busy feeding on a broken tip of a new shoot.

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[1] McCarthy, T and Rubridge, B. 2005. The Story of Earth & Life: a southern African perspective on a 4.6-billion-year journey. Random House Struik: Cape Town (305-306).

[2] McCarthy, T and Rubridge, B. 2005. The Story of Earth & Life: a southern African perspective on a 4.6-billion-year journey. Random House Struik: Cape Town (306).