24 March 2010

Climate catastrophe ushered in the dinosaurs

By
Agence France-Presse
A climatic catastrophe more than 200 million years ago ushered in the age of the dinosaurs by wiping out their rivals, a new study says.
Iceland volcano

Volcanic eruptions in Iceland; powerful volcanic eruptions 200 million years ago decimated crurotarsans and opened the way for dinosaurs. Credit: Icelandic Tourist Board

ATLANTA: A climatic catastrophe more than 200 million years ago ushered in the age of the dinosaurs by wiping out their rivals, a new study says.

An abrupt rise in atmospheric gases, coupled with powerful volcanic eruptions decimated crurotarsans, creatures closely related to today’s crocodiles, according to a study led by Brown University palaeobiologist Jessica Whiteside.

Volcanic activity

The paper, published in the Proceedings of the National Academy of Sciences, was the first to make the link between volcanic activity, climate change and the widespread extinction of a specific animal species.

Scientists gathered fossil evidence of plant and animal extinctions, along with the carbon signature found in the wax of ancient leaves and wood in lake sediments intermixed with basalt that marked the volcanic activity.

Half of all plant species wiped out

They found that huge volcanic eruptions throughout the planet increased the amount of carbon dioxide and other greenhouse gases in the atmosphere, wiping out half of plant species and marking the end of the Triassic period, one of five great mass extinctions of Earth’s history.

More than 200 million years ago, the supercontinent Pangea broke up as the North American and African plates began drifting apart. During their separation, the plates created a basin that eventually became the Atlantic Ocean while fissures cleaved the area.

Nine million square kilometres

Massive outflows of lava ensued, covering over nine million square kilometres, an area about the size of the continental United States.

The volcanic eruptions lasted about 600,000 years.

But the reasons underlying dinosaurs’ survival, diversification and massive size for 160 million years while their crurotarsan foes did not evolve in a similar fashion remains a “mystery,” Whiteside said.

Physiologically superior

One of the main hypotheses is that they were somehow physiologically superior to the crutotarsans, she added. “The truth is that nobody really knows, it just happened at the right place at the right time.”

She said it was a “very complicated” situation similar to the mass extinction and disappearance of dinosaurs when a meteorite hit the Earth.

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