WASHINGTON — The most extensive extinction in history, the dying-out of about 90% of all species 250 million years ago, may have been caused by a massive flow of molten rock that covered an area half the size of Australia to a depth of more than a mile.
A study appearing today in the journal Science suggests the flood of molten rock that created a plateau known as the Siberian Traps in Russia was almost twice as big as previously believed and could have continued for thousands of years, changing the climate of the entire planet.
A group of United Kingdom and Russian scientists says in Science that such an eruption of flood basalt would have filled the planet's atmosphere with a choking concentration of sulfur dioxide, carbon dioxide and other gases.
Samples from the lava flow have been age-dated at about 250 million years. Other studies have shown that during this period the Earth experienced its most extensive extinction crisis--which killed at least 90% of ocean species and more than 70% of land creatures.
Called the Permian-Triassic extinction, it is a key event in the planet's history. It was followed by the rise of the dinosaurs, the animal species that dominated the Earth until they too went extinct about 65 million years ago.
In the study, the researchers analyzed samples drilled from deep below the floor of a basin next to the Siberian Traps. They found the basin was underlain with the same type and age of lava that created the Traps.
This means the flood of lava that formed the Traps was at least twice as massive and lasted perhaps twice as long as previously believed, they said.
Such a large volume of lava spewing to the Earth's surface over hundreds of thousands of years would inject millions of tons of chemicals into the atmosphere, causing long-lasting changes in the climate and an ecological collapse, they said.
The evidence from the new study points toward a prolonged extinction, stretching over hundreds of thousands of years.