Monday, December 04, 2006

The day it rained fire

On a fateful day, 200 000 years ago, it rained fire. A lone stony asteroid, about 30-50 metres in diameter and weighing 300 000 tonnes, streaked through the earth’s atmosphere at 16 kilometres a second. When it smashed into the ground a massive explosion, a hundred times more powerful than the Hiroshima atomic bomb, caused winds of over 1000km/hr to rip across the surrounding landscape, killing everything that happened to be in the area. Anything alive within 24 kilometres of the blast was vaporised, killed or maimed.

200 000 years later, a crater is all that remains of that explosion. The intelligent hominids that populate the earth call it the Tswaing meteor crater, and it is located 40 kilometres north of the city of Pretoria in South Africa. The crater is about 1 kilometre across, 100 metres deep, and is filled with a lake of salty water. The picture on the left is a Landsat image of the site.

On a hot and sunny Saturday three weeks ago, Cori and I, together with Rutger (Cori’s brother visiting from Pietermaritzburg) and Jacomien (a friend of Cori’s) went for an afternoon hike around the crater. The hiking trail is about 7 kilometres long, and runs along the eastern lip of the crater, down into the basin, along the lake and out again towards a museum and picnic area that lies outside.

We started out strong, making our way through the bush and past various ruins that formed part of an old salt mine. We spent time at various viewpoints on the crater lip, admiring the view of the basin, drinking from our water bottles and snacking on apples and packets of Nick Naks (thank you Jacomien for the crisps!). The picture on the right is of me, standing at one of the viewpoints.

It took about three hours for us to complete the circuit. It was easy going until we reached the shore of the saline lake within the basin of the crater. The African summer sun on that particular day was particularly harsh, and within the basin the heat was relentless. Rutger’s face was soon beet red, Jacomien was looking a bit dazed, and even I was starting to straggle behind the group. The only person who didn’t seem to mind was Cori, who chatted away like an auctioneer high on caffeine :-) Despite our travel worn bodies, we finally made our way slowly out of the crater and towards the picnic area.

For me, the crater serves as an ominous reminder of how vulnerable humankind actually is. We run around everyday in the rat-race: we wake up, brush our teeth, rush off to work, fight with the boss and return home with thoughts of supper on our minds. We get so involved with our own lives that we often forget that the cosmos possesses the potential of instantly ending life on earth, or at least changing civilisation as we know it. One can only imagine what damage such an impact would cause if it occurred today in the same spot, or even in a major city like New York or London.

Despite the heat, all four of us enjoyed the hike at Tswaing crater. Not only is it an interesting attraction for those who enjoy astronomy or geology, but it also serves as a warning that we should keep our eyes on the skies.


(Google satellite image of the Tswaing crater)

1 comment:

r10b said...

Very interesting. You are fortunate to be able to go on such adventures. Thanks for sharing.

I woke up to -5C this morning.