Dinosaurs thrived after ice, not fire, says a new study of ancient volcanism

Three-quarters of all living species abruptly vanished during one of the five major mass extinctions that occurred on Earth 206 million years ago. Large volcanic eruptions that tore apart Pangaea, a giant continent that at the time included nearly all of the planet’s land, occurred at the same time as the wipeout. Over a period of 600,000 years, millions of cubic miles of lava erupted, dividing what are now North Africa, Europe, and the Americas.

The Jurassic, when dinosaurs emerged to replace Triassic creatures and rule the planet, began at this time, marking the end of the Triassic.

The main causes of the End Triassic Extinction have long been disputed, but the most common ones are that the carbon dioxide released by the eruptions accumulated over many millennia, raising temperatures to levels that many creatures could not survive and acidifying the oceans.

However, a recent study reveals that the primary cause was cold rather than warmth. According to the study, the initial lava pulses that ended the Triassic were incredible occurrences that lasted less than a century each, rather than spanning hundreds of thousands of years. In the Proceedings of the National Academy of Sciences journal, the study was published.

During this brief period, particles of sulfate that reflect sunlight were thrown into the atmosphere, cooling the planet and freezing many of its people. According to the researchers, volcanic winters caused the most harm, but gradually increasing temperatures in an already hot environment—atmospheric carbon dioxide in the late Triassic was already three times that of today—may have completed the job later.

According to lead author Dennis Kent of the Lamont-Doherty Earth Observatory at the Columbia Climate School, “carbon dioxide and sulfates act not just in opposite ways, but opposite time frames.”. “The effect of sulfates is almost immediate, but the accumulation and heating of carbon dioxide takes a long time. It opens our eyes to the limits of human comprehension. Over the course of a lifetime, these things occurred. “..”.

The Central Atlantic Magmatic Province, or CAMP, eruption has long been assumed to be responsible for the Triassic-Jurassic extinction. Perhaps the most conclusive link was presented by Kent and colleagues in a ground-breaking 2013 study. Paleomagnetism expert Kent found a consistent polarity reversal in sediments immediately beneath the first CAMP eruptions, indicating that they all occurred simultaneously in what are now popular regions of the world.

The beginning of volcanism was then dated by colleagues using radioactive isotopes to 201,564,000 years ago, give or take a few tens of thousands of years. Many believed that the enormous CAMP deposits must have taken many millennia to accumulate, even though scientists were unable to determine the size of the initial eruptions.

Data from CAMP deposits in the Moroccan mountains, along the Bay of Fundy in Nova Scotia, and in the Newark Basin in New Jersey were correlated in the new study by Kent and associates. The alignments of magnetic particles in the rocks that documented the previous drifting of the Earth’s magnetic pole during the eruptions were their main piece of evidence.

This pole deviates from the planet’s constant axis of rotation, or true north, and, as a result, shifts by a few tenths of a degree annually due to a complex web of mechanisms. The explanation for why compasses don’t always point north. ().

This phenomenon causes magnetic particles in lava that was deposited within a few decades of one another to all point in the same direction, whereas lava that was deposited, say, thousands of years later tends to point 20 or 30 degrees in a different direction.

The researchers discovered that there were five consecutive initial CAMP lava pulses that occurred over a period of approximately 40,000 years. Each of these pulses had magnetic particles aligned in a single direction, suggesting that the lava pulse had formed within 100 years before drift of the magnetic pole could show up.

Temperatures are said to have plummeted as a result of these massive eruptions releasing so many sulfates so rapidly that the sun was mainly obscured. The cold spells that result from volcanic sulfate aerosols usually pass quickly because they tend to rain out of the atmosphere within years, unlike carbon dioxide, which lingers for centuries. These volcanic winters were destructive, however, because of the size and speed of the eruptions.

Just the first CAMP pulses were hundreds of times larger, according to the researchers, who compared the CAMP series to sulfates from the Laki volcano eruption in Iceland in 1783, which resulted in extensive crop failures.

Triassic-era fossils can be found in sediments immediately beneath the CAMP layers. These fossils include giant, flat-headed amphibians, strange tree lizards, various tropical plants, and large terrestrial and semiaquatic relatives of crocodiles. The CAMP eruptions then cause them to vanish.

Perhaps because they were small and could live in burrows, small feathered dinosaurs, turtles, true lizards, and mammals had all existed for tens of millions of years prior to this, and they had all survived to eventually flourish and grow significantly larger.

According to Paul Olsen, a paleontologist at Lamont-Doherty, who co-authored the study, “the concentration of the events is related to the magnitude of the environmental effects.”.

The same total volume of volcanism concentrated in less than a century has a far greater impact than small events spaced out over [tens of thousands of years]. The main conclusion is that the CAMP lavas are examples of extremely concentrated events. “..”.