Free Republic

Two billion years ago a meteorite 10km in diameter hit the earth about 100km southwest of Johannesburg, creating an enormous impact crater. This area, near Vredefort in the Free State, is now known as the Vredefort Dome... The meteorite, larger than Table Mountain, caused a thousand-megaton blast of energy. The impact would have vaporised about 70 cubic kilometres of rock - and may have increased the earth's oxygen levels to a degree that made the development of multicellular life possible... The original crater, now eroded away, was probably 250 to 300 kilometres in diameter. It was larger than the Sudbury...

The destructive space rock was somewhere between 12.4 and 15.5 miles wide. The largest asteroid ever to hit Earth, which slammed into the planet around 2 billion years ago, may have been even more massive than scientists previously thought. Based on the size of the Vredefort crater, the enormous impact scar left by the gargantuan space rock in what is now South Africa, researchers recently estimated that the epic impactor could have been around twice as wide as the asteroid that wiped out the nonavian dinosaurs. The Vredefort crater, which is located around 75 miles (120 kilometers) southwest of Johannesburg,...

Billions of years ago... our planet’s primordial atmosphere was toxic to life as we know it, consisting of carbon dioxide, nitrogen and other gases. However, by the Paleoproterozoic Era (2.5–1.6 billion years ago), a dramatic change occurred where oxygen began to be introduced to the atmosphere – known as the Great Oxidation Event (GOE). [S]cientists were not sure if this event – which was the result of photosynthetic bacteria altering the atmosphere – occurred rapidly or not. ... Based on newly-discovered geological evidence, the team concluded that the introduction of oxygen to our atmosphere was “more like a fire hose”...