A massive mega-volcano in what is now the Bay of Fundy has been implicated in a mass-extinction event that helped the dinosaurs rise up as the dominant form of life on the planet.

Dinosaurs 'ruled the Earth' for roughly 135 million years, from the early Jurassic to the late Cretaceous periods (201 million to 66 million years ago). Their reign ended rather abruptly, however they wouldn't have enjoyed it weren't for the End-Triassic Extinction, an event that killed off nearly half of the species on the planet. There's been some debate about exactly what caused this extinction event, as it may have been an asteroid or comet impact, like what happened at the end of the dinosaur's time, but according to a new study published in Science, researchers believe that they have a more terrestrial explanation.

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"This is one of the largest lava flows on Earth here in the Bay of Fundy… and quite capable of producing poisonous gases that affect the Earth's environment in an eruption," said geologist Greg McHone, a co-author of the study who lives on Grand Manan Island, the largest island in the Bay of Fundy.

During the late-Triassic period, Earth looked very different than it does now. The continents we know today were still jammed together in one large continent known as Pangea. At that time, the Atlantic Ocean didn't exist, and what is now western Morocco, eastern Canada and the northeastern United States rested up against each other. When Pangea broke apart, an immense mega-volcano erupted in that region, spreading lava flows out for hundreds of kilometres and creating what is now known as the Central Atlantic Magmatic Province (CAMP).

This massive eruption also spewed tremendous amounts of sulphur dioxide and carbon dioxide into the atmosphere. This first blotting out the Sun's rays, causing a winter that lasted for years, and when the sulphur finally settled to the ground, the planet warmed up again very quickly due to the heat-trapping influence of the carbon dioxide. The stresses due to these rapid shifts in the climate resulted in half the species on Earth dying off in a relatively short time.

According to McHone, some of the difficulty in pinning down how this mass extinction took place was due to inconsistencies in what the rock layers were showing — rock layers in Morocco didn't show the extinction event, whereas layers in Atlantic Canada and the U.S. Northeast did, but they lay underneath the lava flows (thus indicating that the extinction came first).

"So much has been eroded away from the Earth's surface for the last 200 million years," he said.

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The researchers used two different methods to solve the problem. The first relied on analyzing zircon crystals embedded in the lava flows. These crystals trapped uranium as they formed, and the rate at which uranium decays into lead is very well-known. This allowed them to date the lava flows, but this method can't be used on the sediment layers that contain fossils, so for that they turned to a technique called 'astrochronology' — using known changes in Earth's orbit, tilt and precession (known as 'Milankovitch cycles'), as well as solar activity, to precisely date sedimentary rocks.

Using these techniques on rock layers throughout different parts of the Central Atlantic Magmatic Province, including those in New Brunswick and Nova Scotia — on the shores of the Bay of Fundy — the researchers found that the mega-volcano eruption happened 201,564,000 years ago, just before the dinosaurs rose to power.

"When I look out my window, I can see a ridge of this same lava flow that is in the Bay of Fundy, now linked to the mass extinction," said McHone. "So it's quite fun."

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