20/09/2024
WHERE'S THE ROCK?
Giant Vredefort asteroid vaporised
One of the things I'm always asked on Dome tours and briefings is - "Where's the rock? What can we see?"
The fact is that nothing was left of the huge impactor, even at the time. People who come looking for a smallish crater with bits of debris or even a space rock conveniently placed in the middle are going to be disappointed. But it's no disappointment to hear the story of what actually happened and imagine the impact - as shown here in an AI rendering - at the moment of contact with our planet.
For one thing, the multiple rings thrown up up by shockwaves formed mountain ridges, with the inner ring being as high as, or even higher than, the Himalayas - up to 10km high. These burst into existence in a matter of minutes. They have since worn down during two billion years of erosion to about 350 metres high. That's the Dome Bergland (pictured).
Mountain ranges can take ten to 50 million years to form. Not these ones. The Dome Drift river trip that we do down the Vaal takes us floating on calm but moving water right through the inner ring. The river is flat here due its valley having been scoured out by glacial ice in an ice age some 300 million years ago when our subcontinent drifted through the South Pole.
Such wonders of the world can be seen and appreciated on guided tours, either by river, road, on foot or on cycles. We'll take you there, show you the amazing landscape, and show the evidence that is baked into the rocks.
The reason the asteroid completely vaporised is that it was a very large body going incredibly fast: the resulting release of energy as it suddenly stopped was equivalent to - well, at a guesstimate - up to five trillion Hiroshima size nuclear bombs. The rock turned to gas and even plasma. (Plasma is superheated matter – so hot that the electrons are ripped away from the atoms forming an ionized gas.).
The crater that formed had multiple rings, of which three are still visible. The outside ring is the Witwatersrand, stretching from Springs around through Johannesburg and Klerksdorp to Welkom. This is the Arc of Gold where deep strata of gold ore were upended to the surface and buried at a steep angle. The incredible engineering achievement of mining at more than 4km down is another marvel of the world - this time created by us.
If you want to know more about the best preserved impact crater on Earth, twice the size of the one that caused the death of the dinosaurs, contact me for a talk or tour. The roads into and around the crater are open to the public but unless you know what you are looking at it will all be blasted hard to understand. We have a self-drive map and booklet showing it all, that kids can use for school projects.
I'm Prof Graeme Addison, writer on popular science, author of many books and a new one coming - on the crater. Call or WhatsApp me at +27 84 245 2490.
Only an hour south of Joburg! and we have beautiful accommodation too.
