Around 50,000 years ago --- give or take a few centuries -- a rather large chunk of rock came hurtling in from space. As it screamed through the atmosphere, it heated up, lost some of its mass. But enough of it was left over (a meteorite about 60 metres across, weighing in at about a million tonnes) to make a rather large thump when it hit the planet's surface. Not surprisingly, it made a fairly decent sized hole where it landed --- a crater close to two kilometres in diameter, with walls over 130 metres high. The meteor itself --- or what's left of it --- is, various references tell me, buried deep in the earth's crust in the centre of the crater.



