A recently published scientific paper suggests that rapid global cooling as a result of the release of billions of sulphate particles into the atmosphere played a significant role in the End-Triassic extinctions.

The end of the Triassic marks one of the five great mass extinctions recorded in the Phanerozoic Eon. Arguably, of these five, the End-Triassic extinction is the least understood by Earth scientists. The mechanisms of extinction remain open to debate. However, it is known that during this time there was extensive volcanic activity.  Pangaea began to tear itself apart, the first step in a process that led to the creation of the Atlantic Ocean. The Atlantic is still widening today.

Enormous outpourings of basaltic lava occurred covering the entire (modern) eastern seaboard of the United States, reaching as far west as Texas and probably as far south as Venezuela. These basaltic extrusions have counterparts in Europe and northern Africa that are approximately the same age. These huge eruptions are known collectively as the Central Atlantic Magmatic Province (CAMP).

A New Theory to Explain the End-Triassic Extinctions

It had been thought that huge concentrations of carbon dioxide pumped into the atmosphere led to global warming and the acidification of the world’s marine environments.  Intriguingly, a new study suggests it was sudden and dramatic global cooling that led to the extinction of many animals.

This new study suggests that the first eruptions were immense but relative brief events, lasting less than a hundred years each. Sunlight-reflecting sulphate particles were ejected into the atmosphere, rapidly cooling the planet. The extreme cold changed the biota of planet Earth. The Earth’s temperature began to rise with the increase of carbon dioxide in the atmosphere and global warming took place. However, the researchers conclude that it was the rapid freezing that resulted in the collapse of ecosystems and the initial mass extinctions.

The photograph shows red sandstone deposits in Morocco associated with the Triassic to Jurassic boundary. Red sediments in many locations around the world contain fossils of Triassic fauna and flora. The white caps are sediments laid down by extensive volcanism, as is evidenced by the grey/black basalt layers topping the assemblage. Picture credit: Paul Olsen/Lamont-Doherty Earth Observatory.

Picture credit: Paul Olsen/Lamont-Doherty Earth Observatory

Lead author of the paper, Dennis Kent, Adjunct Senior Research Scientist at Lamont-Doherty Earth Observatory at Columbia University, stated:

“It takes a long time for carbon dioxide to build up and heat things, but the effect of sulphates is pretty much instant. It brings us into the realm of what humans can grasp. These events happened in the span of a lifetime.”

To read another article about Triassic extinction theories: The Carnian Pluvial Episode and Extinction.

Correlating Data from CAMP Deposits

The researchers gathered data from CAMP deposits in the mountains of Morocco, in the Bay of Fundy (Nova Scotia) and from the Newark Basin (New Jersey). The focused their study on the alignment of magnetic particles within the strata. The orientation of these particles records the historical drift of the Earth’s magnetic pole during the time of the volcanic activity.

The magnetic pole is not fixed, it shifts from the planet’s stable axis of rotation—true north—and changes position by a few tenths of a degree each year. This is why compasses do not point at true north. As a result, magnetic particles in lava flows that occurred within a few decades of each other will align in the same direction, whereas those from thousands of years later could be misaligned by twenty to thirty degrees.

Red Triassic sandstones capped by volcanic ash in the Bay of Fundy (Nova Scotia). Picture credit: Paul Olsen/Lamont-Doherty Earth Observatory.

Picture credit: Paul Olsen/Lamont-Doherty Earth Observatory

Five successive pulses of the Central Atlantic Magmatic Province (CAMP) lava were identified. These pulses covered a time span of approximately 40,000 years. Each lava pulse exhibited magnetic particle alignment in a single direction, suggesting that these eruptions happened within a window of around a hundred years. This is far too short a period of time for significant magnetic pole drift to occur.

The research team concluded that these eruptions released huge amounts of sulphates into the atmosphere. These particles blocked sunlight and led to global temperatures plummeting. Carbon dioxide can remain in the atmosphere for centuries. However, volcanic sulphate aerosols are dissipated within a few years. Consequently, while these volcanic winters were extreme, their duration was relatively short.

The researchers likened the CAMP episodes to the sulphate emissions from the 1783 eruption of Iceland’s Laki volcano, which triggered one of the coldest years on record and caused widespread crop failures. However, it is emphasised that the CAMP eruptions were hundreds of times more powerful.

Everything Dinosaur acknowledges the assistance of a media release from The Earth Institute/Columbia Climate School (Columbia University) in the compilation of this article.

The scientific paper: “Correlation of sub-centennial-scale pulses of initial Central Atlantic Magmatic Province lavas and the end-Triassic extinctions” by Dennis V. Kent, Paul E. Olsen, Huapei Wang and Mohammed Et-Touhami published in the Proceedings of the National Academy of Sciences.