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The Vredefort Dome is an enormous impact crater in South Africa. It is a UNESCO World Heritage Site, and has been since 2005. The Vredefort Dome is also known as the Vredefort crater or the Vredefort impact structure, and is the largest attested impact crater on the planet.
The Vredefort Dome is an impact crater more than 185 miles (300km) in diameter, making it the largest confirmed impact crater on Earth. The Wilkes Land crater, found in Antarctica, is more than 300 miles (500km) in diameter, but is not confirmed to be the result of an asteroid hitting the earth. The next largest impact crater on Earth is the Sudbury Basin in Canada, which is just over 150 miles (250km) in diameter.
The Vredefort Dome is also the second-oldest known crater on the planet, at a bit more than 2 billion years old. This is just a few hundred million years younger than the Suavjärvi crater in Russia. This places the asteroid that impacted the earth to cause the Vredefort Dome sometime during the Paleoproterozoic age of the Earth, when the first Cyanobacteria appeared, helping to elevate oxygen levels throughout the planet.
It is possible that the very impact of the asteroid that formed the Vredefort Dome released enough oxygen into the atmosphere that it actually led to the evolution of Cyanobacteria. If this were the case, then the Vredefort Dome would represent a physical trace of one of the most important events in the history of life on the planet, as from that point on creatures began to evolve more and more to respirate oxygen, ultimately leading to more complex life forms, including humans themselves.
The asteroid that struck the earth was probably somewhere in the range of 6 miles (10km) in diameter, larger than many mountains. When it struck the Earth, the asteroid would have released a thousand-megatons of force, instantly vaporizing more than 15 cubic miles (70 cubic km) of the planet itself. That’s the equivalent of a thousand of the most powerful active nuclear bombs on the planet, or a billion tons of TNT exploding at once.
The Vredefort impact crater consists of many different rings of rock that was uplifted when the asteroid struck. Although many of the rings have since eroded away, some are still very visible, particularly from the air. The Vredefort Dome itself, as outlined by UNESCO, is the inner ring of the original impact crater, measuring some 110 miles (180km) in diameter.
A burgeoning tourist infrastructure has begun around the Vredefort Dome, and tours, information, and lodging are all now available in the area. Paths run through the entire area, and activities such as hiking, biking, and horseback riding offer opportunities to take in the enormous dome. River rafting trips also run along the rivers, giving a unique perspective of the uplifted granite and other stone forced out of the earth during the initial asteroid impact.