Saturday, March 21, 2015

The Vredefort Impact Dome

We visited our last UNESCO World Heritage Site in South Africa, the Vredefort Impact Dome, the site of the biggest meteorite impact that geologists have yet found on earth. (SA's other World Heritage Sites are Robben IslandiSimangaliso Wetland Park, the Cradle of Humankind, uKhahlamba-Drakensberg Park, Mapungubwe Cultural Landscape, the Richtersveld Cultural and Botanical Landscape and the Cape Floral Region.)

World Heritage Sites are designated for a variety of reasons. Cultural significance. The site of significant historic events. Scientific importance. The UNESCO World Heritage committee gave three reasons why Vredefort was considered worthy of its designation. First, for the preservation of the unique geology due to the meteor impact and its affect on the surrounding area. Second, the fact that the rings marking the impact are still visible for viewing and third, that it is located in a safe and quiet area which provides enjoyment for visitors.

the Eiffel Tower in Parys
The gateway to the Vredefort Dome area is Parys. On the banks of the Vaal River, Parys has a very relaxed riverside feel. The small town is filled with art galleries and antique shops and is known as a purveyor of Afrikaans culture and food.

We stopped at the information center to get the lay of the land and contact information for a local guide to take us to the Vredefort Dome. We were given Christo's name and contact information. Christo owns a 200 hectare farm within the World Heritage Site. His farm near Parys has the distinction of containing a high point where you can see the rings of the impact crater. (His contact number is 083 406 0841.)
Christo's farm is also home to the Kopieskrall Country Lodge and that is where we met him to drop of our car and start our tour.














close up of the black veins


Make a right at the granite slab.

Vredefort granophyre and pseudotachylite are the names given to the black crystallized impact melt-rock that flowed into the cracks of the granite. They contain broken pieces from many rock types as well as very small chemical traces of the meteorite that caused the impact.











blesbok

Most of the World Heritage Site is privately owned by individual farms and families.
"Hey, a farm dog!"











We brought Lou & Serge with us and they immediately made friends with Christo's dog Milo.









Christo and Vince and the 40 year old Landcruiser

back of the bakkie with Lou & Serge for an African massage

First, Christo gave us some history in the lapa before heading up to the view site

ready for the ride to the top!

inside the ancient kraal
On the top of the ridge is an old abandoned Tswana kraal. The former inhabitants were chased into what is now Botswana by Shaka during his conquest across southern Africa to unite the tribes.

We took our sons to visit USA's Meteor Crater in Arizona once so I thought I was prepared for what we were about to see. But the numbers make it impossible to recreate an image in a photograph that would convey the impact of the meteor on the landscape. The meteor is estimated to have been between 10 and 15 kms in diameter and upon impact - traveling at an estimated 10 kms per second - with the earth, it made a crater that was more than 300 kms in diameter!

It was nearly twice as big as the impact that killed the dinosaurs 65 million years ago. Besides being the biggest impact crater, Vredefort is also the oldest impact event. The meteor impact happened some 2023 million years ago at a time when there were no people nor animals and plants like the ones we see today. Probably the only thing living at the time of the impact were single-celled organisms. And curiously, scientists speculate that the incident may have increased the planet's oxygen level's to the point of making life possible.

The Vredefort Dome is only the central part of the impact crater. It was called a dome because the rock layers were bent into the shape of an upside-down bowl 90 kms across by the impact.


Today the edges of the Vredefort Dome are exposed in several rings which can been seen from the top of Christo's hill.



Probably the biggest effect the meteor impact had on the area though concerns the accessibility of the gold in the Witwatersrand. Gold sediment originally lie buried deep on the bottom of the ridge. But when the meteor hit, it caused the Wits gold layer to tilt and reach the surface. It is possible that if it had not been for the Vredefort impact, the gold of Johannesburg would never have been discovered.
All over the floor of the impact area you can also see a number of outcroppings of Parys granite, a rare pink granite that was mined in the last century.

"Enough of the African massage. We want to ride up front on the way back!"

No comments:

Post a Comment