Death in the deep: Volcanoes blamed for mass extinction

PARIS (AFP) — Ninety-three million years ago, Earth was a reshuffled jigsaw of continents, a hothouse where the average temperature was nearly twice that of today.

Palm trees grew in what would be Alaska, large reptiles roamed in northern Canada and the ice-free Arctic Ocean warmed to the equivalent of a tepid swimming pool.

So our planet was balmy -- but hardly a biological paradise, for it was whacked by a mass die-out. The depths of the ocean suddenly became starved of oxygen, wiping out swathes of marine life.

The extinction was so spectacular that, helped by a suddenly sluggish shift in ocean circulation, the remains of the tiny victims littered the sea bed in thick layers, and over geological time became transformed into oil.

After the extinction, levels of greenhouse gases in the atmosphere dropped and Earth lurched into a sudden, but short-lived, period of cooling. ...