Dinosaurs Were Not The First To Die Out 65 Million Years Ago

[n2doc]

Sixty-five million years ago, the most studied mass extinction in Earth’s history happened and the dinosaurs were wiped off the planet. A new study from the University of Washington, published in Palaeogeography, Palaeoclimatology, Palaeoecology, indicates that a separate extinction came shortly before that, triggered by volcanic eruptions that warmed the planet and killed life on the ocean floor.

A six-mile wide asteroid slamming into Mexico’s Yucatan Peninsula is thought to have caused the dinosaur extinction event. New evidence shows that by the time of that impact, life on the seafloor – mostly species of clams and snails – was already dying out because of huge volcanic eruptions along the Deccan Plateau in what is now India.

“The eruptions started 300,000 to 200,000 years before the impact, and they may have lasted 100,000 years,” said Thomas Tobin, a UW doctoral student in Earth and space sciences.

The volcanic eruptions would have filled the prehistoric atmosphere with fine particles, called aerosols, that initially cooled the planet. More importantly, they would also have spewed carbon dioxide and other greenhouse gases to produce long-term warming that led to the first of the two mass extinctions.
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http://www.redorbit.com/news/science/1112688403/extinction-events-volcanic-eruptions-090612/

[Warpy]

1. Thinking now is that the impact just finished off the stragglers

and that the great dieoff had been happening for some time due to the massive vulcanism that produced the Deccan Traps in India.

Likely they were stressed enough that they were also falling victim to epidemics of diseases they'd always taken in stride when conditions were favorable.

[Odin2005]

2. That is what I think, too.

The vulcanism in India and North America lead to rapid warming of the climate that disrupted ecosystems and made them vulnerable to the impact event. Either alone would have only caused a minor mass extinction, it took both together to cause catastrophe.