Asteroid impact, volcanoes led to mass extinction on Earth

Geologists from the University of Berkeley have unearthed compelling evidence that an asteroid impact on Earth 66 million years ago accelerated the eruptions of volcanoes in Deccan Traps in west-central India for thousands of years.

This double whammy - huge asteroid impact and erupting volcanoes - caused the extinction of many land and marine animals, including the dinosaurs, the team noted.

Deccan Traps are a large province located on the Deccan plateau of west-central India and one of the largest volcanic features on Earth.

The new evidence includes the most accurate dates yet for the volcanic eruptions before and after the impact.

The new dates showed that the Deccan Traps lava flows, which at the time were erupting at a slower pace, doubled in output within 50,000 years of the asteroid or comet impact that is thought to have initiated the last mass extinction on Earth.

Both the impact and the volcanism would have blanketed the planet with dust and noxious fumes, drastically changing the climate and sending many species to an early grave.

"Based on our dating of the lavas, we can be pretty certain that the volcanism and the impact occurred within 50,000 years of the extinction," explained lead researcher Paul Renne, professor of earth and planetary science and director of the Berkeley Geochronology Centre.

The geologists argue that the impact abruptly changed the volcanoes' plumbing system which produced major changes in the chemistry and frequency of the eruptions.

For the study, the team last year collected lava samples from throughout the Deccan Traps east of Mumbai, sampling flows from near the beginning, several hundred thousand years before the extinction and near the end.

High-precision isotope dating technology allowed them to establish the chronology of the flows and the rate of flow over time.

In the paper, they describe major changes in the Deccan Traps volcanism, which was probably "bubbling along happily, continuously and relatively slowly" before the extinction.

After the asteroid impact, the eruption rate more than doubled and the volcanism became more punctuated, with more voluminous lava flows interspersed with long periods of quiet.

According to the authors, a large nearby earthquake of a magnitude 8, 9 or 10 could also have reignited the Deccan Trap flows.

In fact, large quakes may have rattled underground magma chambers and ignited eruptions throughout Earth's history.

The team described the findings in the journal Science.