The end-Triassic extinction is, along with the end-Permian and end-Cretaceous events, the most severe mass extinctions of the past 270 million years. The exact mechanism of the end-Triassic extinction has long been debated, most notably because the carbon dioxide that had accumulated over thousands of years and appeared on the surface from volcanic eruptions was a persistent This caused temperatures to rise to impossible levels and seawater to become more acidic. but, new paper in Proceedings of the National Academy of Sciences I say the opposite. The main cause is not warmth, but cold.

The end-Triassic mass extinction occurred 201,564,000 years ago, resulting in the extinction of approximately 76% of all marine and terrestrial species.

This mass extinction coincided with a massive volcanic eruption that split the supercontinent Pangea.

millions of kilometers³ Over 600,000 years, lava erupted and separated what is now the Americas, Europe, and North Africa.

This event marked the end of the Triassic period and the beginning of the Jurassic period. The Jurassic period was the period when dinosaurs appeared to replace the Triassic period creatures and dominated the Earth.

A new study provides evidence that the first lava pulses that ended the Triassic period were extraordinary events that each lasted less than a century, rather than hundreds of thousands of years.

During this condensed time frame, sunlight-reflecting sulfate particles spewed into the atmosphere, cooling the Earth and freezing many of its inhabitants.

A gradual rise in temperature in an already hot environment (carbon dioxide in the atmosphere during the Late Triassic was already three times higher than today's levels) may have finished the job later, but it caused the most damage. It was a volcanic winter.

“Carbon dioxide and sulfate not only act in opposite ways, but in opposite time frames,” said Dr. Dennis Kent, a researcher at the Lamont-Doherty Earth Observatory.

“While it takes a long time for carbon dioxide to build up and heat up objects, the effects of sulfates are almost instantaneous. It takes us into the realm of human grasp. These The events happened in a lifetime.”

The Triassic-Jurassic extinction has long been thought to be related to so-called atmospheric eruptions. mid-atlantic magma zone (camp).

In their study, Dr. Kent and colleagues correlated data from CAMP deposits in the mountains of Morocco, along the Bay of Fundy in Nova Scotia, and in New Jersey's Newark Basin.

A key piece of evidence is the arrangement of magnetic particles in rocks that record the past drift of Earth's magnetic poles during eruptions.

Through a complex series of processes, this pole is offset from the planet's fixed axis of rotation, or true north, and its position changes by a tenth of a degree each year.

Because of this phenomenon, magnetic particles in lava that are placed within decades of each other all point in the same direction, but those placed, say, thousands of years later, point in different directions by 20 or 30 degrees.

What the researchers discovered were five consecutive early CAMP lava pulses spread over about 40,000 years. Each magnetic grain is aligned in a single direction, indicating that the lava pulse appeared less than 100 years before magnetic drift appeared.

These large eruptions released so much sulfate so quickly that it blocked most of the sun and lowered temperatures.

Unlike carbon dioxide, which lingers for centuries, volcanic sulfate aerosols tend to rain out of the atmosphere within a few years, so the resulting cold snaps don't last very long.

However, due to the speed and scale of the eruptions, these volcanoes' winters were devastating.

Scientists compared the CAMP series to sulfates produced in the 1783 eruption of Iceland's Laki volcano, which caused widespread crop failure. Only the first CAMP pulse was several hundred times larger.

Triassic fossils lie in the sediments just below the CAMP layer. This includes large terrestrial and semi-aquatic relatives of crocodiles, strange tree lizards, giant flat-headed amphibians, and many tropical plants. After that, it disappears with the eruption of CAMP.

Small feathered dinosaurs existed for tens of millions of years before this, surviving along with turtles, true lizards, and mammals, and eventually thriving to become much larger. This is probably because they are small and able to survive in burrows.

“The magnitude of the environmental impact is related to the concentration of events,” said Dr. Paul Olsen, also of the Lamont-Doherty Earth Observatory.

“A small event spread over tens of thousands of years has a much smaller impact than the same amount of volcanic activity concentrated over less than a century.”

“The most important implication is that CAMP's lava represents an unusually concentrated event.”

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Dennis V. Kent others. 2024. Correlation of sub-centennial-scale pulses of early mid-Atlantic magmatic field lavas and the end-Triassic extinction. PNAS 121 (46): e2415486121;doi: 10.1073/pnas.2415486121