January 7, 1999
Web posted at: 12:20 p.m. EDT (1220 GMT)

By Environmental News Network staff

Most of the volcanic activity didn't resemble spectacular eruptions. Instead, the eruptions were "basaltic" and tons of lava oozed out, and carbon dioxide floated skyward like this much smaller-scale activity at Hawaii's Pu`u`O`o in the early 1990s.

Fossilized bones from several crocodile-like beasts known as champsosaurs have provided evidence of Arctic warming during the late Cretaceous period, scientists report recently in the journal Science.

The fossils indicate that at least once in Earth's history high amounts of the greenhouse gas carbon dioxide warmed Earth to much higher temperatures than usual, according to scientists at the University of Rochester in Rochester, N.Y.

The carbon dioxide was spewed by massive volcanic eruptions about 90 million years ago and as a result, Arctic temperatures were as warm as present-day Florida.

The University of Rochester research team that analyzed the bones estimates that the annual mean temperature in the Arctic during the late Cretaceous period from about 92 million to 86 million years ago, was about 57 degrees Fahrenheit. That means it was rarely, if ever, freezing during the winter, and summer temperatures consistently reached into the 80s and 90s.

The bones come from a layer of sediment right on top of 1,000 feet of hardened lava, known as basalt, and below a layer of marine rock common in the Arctic. That dates the fossils to the period immediately after the volcanism ended.

"I had been looking for rocks from this layer for many years -- in most places the layer doesn't exist or has worn away," said John Tarduno, a geophysicist who studies Earth's magnetic field at Rochester University.

The fossils locked-in a record of what was happening in the Arctic just as extreme volcanism around the planet was winding down. Most of the volcanic activity didn't resemble spectacular eruptions like Mt. Pinatubo. Instead, the eruptions were "basaltic" -- tons of lava oozed out, and carbon dioxide floated skyward.

Besides huge amounts of lava in the Arctic, where hardened lava rock today measures more than a kilometer thick in some places, magma oozed from volcanoes in the Caribbean, in the Pacific Ocean northeast of Australia, in the Indian Ocean, off the coasts of Madagascar and Brazil, in South Africa and in the southwestern United States.

Scientists have long considered the Cretaceous period, which lasted from 144 million to 65 million years ago, a warm time period and a possible model of the greenhouse effect, where gases like carbon dioxide collect in the atmosphere and trapped heat, causing global warming.

Understanding how warming happened in the past helps scientists predict how our planet might react in the future to the increased carbon dioxide being pumped into the atmosphere from car exhaust, coal plants and other burning of fossil fuels.

"We can't avoid the fact that these fossils are sitting right on top of this extremely large volcanic eruption," said Tarduno. "And if you look around the world, it was an unusually active time, with many eruptions occurring at the same time. It's very reasonable to suggest that so much CO2 was dumped into the atmosphere that it overwhelmed the system, causing global warming."

The bones the team found come from what was likely a freshwater bay on Axel Heiberg Island in the high Canadian Arctic at 79 degrees latitude. During the Cretaceous the island was a bit south of where it is today but was still well within the Arctic Circle.

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