Meteorite impact. The danger from space and South Africa's mega-impact the Vredefort structure/ Столкновение с метеоритами. Опасность из космоса и Южноафриканское мега-столкновение структура Вредефорт

Two thousand million years (Ma) ago a mountain-sized bolide from Space, travelling at tens of thousands of kilometres per hour, slammed into the Earth at a position approximately 120 km southwest of the present-day city of Johannesburg, in the vicinity of the present towns of Vredefort and Parys. Within moments, it had blown a hole tens of kilometres deep and more than 100 km wide into the crust of the Earth. Th e force of the impact hurled countless millions of tonnes of rock, some of it heated to temperatures of thousands of degrees centigrade (°C), around the crater over an area extending for hundreds of kilometres from the impact site (Fig. 3a). Fine dust particles and toxic chemicals from the vaporisation of the rock were thrown into the upper atmosphere where they spread around the Earth, blotting out the rays of the Sun for years, causing an unnatural global winter and widespread pollution. Fallout from this massive dust cloud settled through the atmosphere and was deposited all around the world. Th e blast wave from the explosion travelled through rock, air and water, triggering secondary catastrophes, such as earthquakes, landslides and tsunamis (giant fl ood waves in oceans) across the planet. At the point of impact itself, the initial crater lasted no more than a couple of minutes before its walls started to collapse and its fl oor started to rebound as the tremendous compression by the shock wave passed downwards and outwards. Within 10 minutes of the projectile having entered the atmosphere of the Earth, a circular crater 1–2 km deep and up to 250–300 km wide, fi lled with broken rock and superheated melt, scarred the landscape of the then existing continent. A huge impact crater, such as those still visible on the surface of the Moon (Fig. 3c), had formed. Th e greatest single geological catastrophe yet recorded on the face of our planet was largely, but not completely, over. <...>