DOOOOOFFFFFFFF

I recently downloaded and watched a rivetting documentary called Out of the Blue - The Definitive Investigation of the UFO Phenomenon. Narrated by Peter Coyote, the very latest material has been compiled. Video footage and interviews have been collected from France, Russia, Mexico, Brazil, the United Kingdom and the USA.

The most gobsmacking visual provided was a video clip of a missile designed for nuclear capability, that was tracked by some sort of object capable not only of pacing the missile, but zigzagging easily around it. At one point a beam of light, not a lazer, but just a sort of energy beam, seems to flare off the object and at the moment of contact with the missile, the missile explodes. If it's not special digital effects, then there's very little else it could be.

This piqued my interest in space, and space stuff, but I chanced upon this information of a huge impact right in my backyard. I only discovered it because I googled 'travelling South Africa' in search of a map image I could use for my blog. Suddenly I was reading about this explosion, the biggest, apparently that we have evidence of on Earth, ever, just outside Johannesburg.

In 1990, while I was serving in the Air Force, I used to drive from my hometown of Bloemfontein, through Vredefort and Parys, to Johannesburg and Pretoria every weekend, for over 6 months. The stretch between Vredefort and Parys sticks in my mind because it is such a bumpy, curvy, convoluted route in comparison to the straight highways everywhere else. I also remember it because once, as a dare to myself, I turned the lights of the car off and drove for as long as I could in the absolute inky blackness outside Parys at night.

Below are a number of interesting exerpts from geologists or other informed people. It's interesting to note that the last big hit the Earth took was just under a hundred years ago, in Tunguska Northern Siberia in 1908. On average, we're supposed to have a rock land somewhere on Earth every hundred years. So we have 4 more years. So once Bush is gone, it's anyone's guess.


http://www.otters.co.za/blast_from_past.htm:

If anything has a claim to being goddess of the sky, it is the roving asteroid that paid us a visit that day. Some 10-15km in diameter, travelling at a speed of 10-20km per second, it slammed into the earth with a force experts estimate to have been about 87 million megatons. As one megaton equals a million tons of TNT, and the Hiroshima nuclear bomb was only one-fifth of a megaton (20 kilotons), the cosmic bomb was infinitely worse than anything mankind is able to detonate.

The Vredefort crater, estimated at 320km in diameter, is one of three known massive impact sites amongst many hundreds or even thousands of meteorite blemishes on the earth. The other two really large sites are at Sudbury in Ontario, Canada, and Chicxulub on Mexico’s Yucatan Peninsula. The Sudbury area has the dubious record of being the target area of two major hits: the first, almost as ancient as Vredefort, causing a 200km-wide crater, and the second a smaller one just 37 million years ago.

Before Vredefort, the largest and (still the most famous) crater was Chicxulub (pronounced CHEEK-shoe-lube). This impact was almost certainly the cause of the extinction of the dinosaurs about 65 million years ago, the clouds of dust following it blanketed the earth and killed most animal life.

What happened in the Vredefort blast? Like a drop of water falling into a pond, the asteroid punched a hole in the earth’s crust and caused a recoil of molten matter into the atmosphere. The meteorite itself vaporised in the explosion, and the earth was liquidised down to at least 10km as the crater walls slumped inwards, effectively capsizing part of the crust. What we can see today are merely the remnants, like broken teeth in a skeleton’s jaw, of the mountainous upwelling that has eroded over the past 2 billion years.

The effect of it all was to bury, deep down, the gold-bearing strata of the older Witwatersand basin. As the “astrobleme” (eroded crater) was worn away, so the tilted strata of the gold reefs were exposed—and this also explains why the gold industy is perched in a ring around Vredefort (see map). South Africa has the meteorite to thank for first preserving, then exposing, its mineral riches in the upturned edges of the Witwatersrand basin, which have now broken the surface.

Asteroids are actively sought and plotted by astronomers around the world because of their potential for causing devastation on Earth, and there are known to be a few big ones on their way towards us in the next few decades. Unlike many of these “near-earth objects” which harmlessly pass us by, the Vredefort meteorite struck with the force of a cosmic ultrabomb. This occurred towards the end of a long period of cratering by space objects, and we have no way of knowing how many blasts there were or how big they were.

It is estimated that a 1 km-size asteroid impacts the Earth every million years. Smaller asteroid impacts, with the force of a several kiloton nuclear weapon, occur several times a year in the upper atmosphere, and cause extensive damage on the ground about every 100 years—as they did at Tunguska Northern Siberia in 1908 when a 30 meter asteroid exploded, flattening and burning the forests.

http://www.gps.caltech.edu/news/features/southafrica/
day01.html:
The Vredefort impact occurred 2.0 billion years ago and the structure is the largest and oldest impact crater on Earth. The map shows dark pink granulite and pink granite surrounded by orange and brown overturned sediment layers. The granite plug in the center of the impact is about 50 km across.

http://www.hartrao.ac.za/other/vredefort/vredefort.html:
The white dots running in a band along the Witwatersrand are not clouds, they are the waste dumps from the gold mines along the south side of the Witwatersrand. West of Johannesburg and due north of Vredefort can be seen the gold mine dumps of Carletonville. The gold mines of Klerksdorp and Welkom lie north-west and south-west of Vredefort, and their dumps are also easily seen. Is this half ring of gold mines around Vredefort a coincidence?

Evidence has been found by geologists that the cause of this upliftment was an extreme impact event, caused by an asteroid some 10 kilometres in diameter. The ring of hills we see now are the eroded remains of a dome created by the rebound of the rock below the impact site after the asteroid hit. The original crater, now eroded away, is estimated to have been 250 - 300 kilometres in diameter. Some 70 cubic kilometres of rock would have been vaporised in the impact.

The Vredefort structure is currently regarded the biggest and oldest clearly visible impact structure on Earth. It just beats the Sudbury impact structure in Canada for this ranking. The Sudbury structure is some 200 km in diameter and is estimated to be 1.85 billion years old.

Evidence for four impacts even older than than Vredefort, that occurred 3.2 to 3.5 billion years ago, has been found in the greenstone rocks around Barberton in South Africa and corresponding rocks in the eastern Pilbara block of Western Australia. However, these impacts are no longer recognizable as structures on the surface like Vredefort's.

The force of the impact produced deep fractures in the underlying rock. Rock melted by the impact flowed down into the cracks, producing what are now exposed as ridges of hard dark rock - the granophyre dykes. This contrasts with normal geological dykes, where molten rock from deeper in the earth has flowed upwards through cracks in the rock above.