"We think the first volcanic eruptions began about 61 million years ago and then it took another 5 million years for the mantle to weaken, the continent to thin and the molten material to rise to the surface," Duncan said. "It was like lifting a lid. The plate came apart and gave birth to the North Atlantic Ocean."
The link from the volcanism to the warming period came through correlations with the marine fossil record. Dramatic changes in the carbon-isotopic composition of the ocean, corroded plankton shells, and the extinction of some bottom-dwelling organisms characterize the PETM. This interval occurred about 300,000 years before the ash layer, at the peak of volcanic activity in east Greenland.
The scientists speculate that massive release of greenhouse gases ?carbon dioxide and methane ?from the "out-gassing" of the lava flows and heating of organic-rich sediments in basins along the east Greenland margin were responsible for the global warming and changes in ocean chemistry.
The breakthrough came from being able to find a marker ?the ash eruption ?that was distributed all over the North Atlantic, and showed up in the marine record as well, Duncan said.
The volcanic activity that took place in Greenland 55 to 61 million years ago brought up some 10 million cubic kilometers of magma from below the Earth’s surface. These lava flows can be plainly seen today in Greenland, western Scotland and the Faeroe Islands, where they cooled, leaving a layered sequence of lava flows as deep as six kilometers in some places. Duncan said the eruptions are similar in scale with the well-known Deccan Flood Basalts in India.
"They are also about 40 times as big as the Columbia River basalts in Oregon and Washington," he said.
The Columbia River basalts likely had few global impacts, but the Deccan Flood Basalts, the Siberian Traps, and the Parana Flood Basalts in South Ame
Source:Oregon State University