Gold rises in bubbles to Earth's surface

Valuable metals like gold, copper and platinum, reach the Earth's surface from deep underground by floating up on vapour bubbles.  The findings may also provide support for one hypothesis explaining the greatest mass extinction event in Earth's history.  Known as the great dying, the Permian-Triassic extinction event 252 million years ago killed off 70 per cent of terrestrial and 96 per cent of all marine life on Earth. Its cause remains a mystery.