A volcanic eruption nearly obliterated all life on earth 260 million years ago, new research has revealed.

The blast was on a scale that has never been seen by humans and happened even before dinosaurs came along when Earth teemed with creatures which are now extinct.

Lava and ash spewed up from beneath a shallow ocean that once covered Emeishan in southwestern China and rained down on primitive plants and animals across a single supercontinent known as Pangea - which later split into Africa, South America, Australia and Antarctica.

It unleashed around half a million cubic kilometres of lava, covering an area five times the size of Wales.

Scientists were able to pinpoint the exact timing of the eruption and directly link it to a mass extinction event because the lava appears now as a distinctive layer of igneous rock formed from magma sandwiched between sedimentary rock containing easily datable fossilised marine life.

Palaeontologist Professor Paul Wignall, of the University of Leeds, said: "When fast flowing, low viscosity magma meets shallow sea it's like throwing water into a chip pan there's spectacular explosion producing gigantic clouds of steam."

The injection of sulphur dioxide into the atmosphere - caused by the lava mixing with water - would have lead to massive cloud formation spreading around the world.

This cooled the planet and ultimately resulted in a torrent of acid rain. Scientists estimate from the fossil record that the environmental disaster happened at the start of the eruption.

Geologists generally agree a number of important events in Earth's history happened around this time including the break-up of Pangaea - the original super continent- and a likely change in planetary climate.

There was also a mass extinction of life on Earth when 96 percent of all ocean species and about 70 percent of all land species became extinct.

Giant explosive eruptions such as these may have impacted the planet's climate because large eruption columns could spread ash particles and toxic gasses into the upper atmosphere and around the globe.

Added Prof Wignall, whose findings are published in Science: "The abrupt extinction of marine life we can clearly see in the fossil record firmly links giant volcanic eruptions with global environmental catastrophe, a correlation that has often been controversial."