201.6 million years ago, one of the five major mass extinctions on Earth occurred, when three-quarters of all species suddenly disappeared. This annihilation coincided with a massive volcanic eruption that tore apart Pangaea, a massive continent that at the time occupied almost all of the planet’s landmass. Over about 600,000 years, millions of cubic miles of lava erupted, separating what is now the Americas, Europe, and North Africa. This marks the end of the Triassic period and the beginning of the Jurassic period, when dinosaurs emerged to rule the Earth, replacing Triassic creatures.
The exact mechanism is Triassic extinction ends It has long been debated, but the most striking point is that the explosions, which formed over thousands of years, released carbon dioxide at the surface, raising temperatures and acidifying the oceans to levels unsustainable for many living things. But a new study shows just the opposite. Cold, not warmth, was the main culprit. This study provides evidence that the first lava pulses that ended the Triassic were massive events that each lasted less than 100 years, rather than lasting hundreds of thousands of years. During this compressed period, sunlight-reflecting sulfate particles were ejected into the atmosphere, cooling the planet and freezing many of its inhabitants. Gradually rising temperatures in an initially hot environment (atmospheric carbon dioxide was already three times today’s level at the end of the Triassic) may have gotten the job done later, but it was the volcanic winters that did the most damage, researchers say.
“Not only do carbon dioxide and sulfate act in opposite directions, but time also acts in opposite directions,” said the lead author. Dennis Kent Columbia Climate School’s Lamont-Doherty Earth Observatory. “It takes a long time for carbon dioxide to build up and heat things up, but the effects of sulfates are almost instantaneous. It takes us into the realm of human understanding. These incidents have happened throughout my life.”
The study was recently published in the journal Proceedings of the National Academy of Sciences.
The Triassic-Jurassic extinction has long been thought to be linked to the eruption of the so-called Central Atlantic Magma Region (CAMP). In a groundbreaking 2013 study, Kent and colleagues provided perhaps the clearest link yet. Kent, who studies paleomagnetism, has identified consistent polarity reversals in sediments directly beneath the early CAMP eruptions, showing that they all occurred simultaneously in what are now widespread locations around the world. The colleagues then used radioactive isotopes to estimate when volcanic activity began around 201,564,000 years ago, or tens of thousands of years ago. Scientists could not say how large the initial explosion was, but many speculated that it may have taken thousands of years for the massive CAMP deposits to form.
In the new study, Kent and colleagues correlated data from CAMP deposits in the Moroccan Mountains along the Bay of Fundy in Nova Scotia and the Newark Basin in New Jersey. Their main evidence is the alignment of magnetic particles in rocks that record the past drift of the Earth’s magnetic poles during volcanic eruptions. Due to a series of complex processes, this pole is offset from the planet’s unchanging axis of rotation (true north), changing its position by tens of degrees each year. (Why a compass doesn’t point exactly north) Because of this phenomenon, magnetic particles in lava formed within a few decades will all point in the same direction, and magnetic particles in lava formed after thousands of years will all point in the same direction. Point 20 or 30 degrees in the other direction.
What the researchers discovered were five successive early CAMP lava pulses spread out over about 40,000 years. Each magnetic particle was aligned in a single direction. This indicates that the lava pulse appeared less than 100 years before magnetic drift occurred. They say this huge explosion released so much sulfate so quickly that it blocked out most of the sun and caused temperatures to plummet. Unlike carbon dioxide, which persists for centuries, volcanic sulfate aerosols tend to rain out of the atmosphere within a few years, so the resulting cold snap does not last long. However, the speed and scale of volcanic eruptions made these volcanic winters devastating. The researchers compared the CAMP series to sulfates from the 1783 eruption of Iceland’s Laki volcano. The volcano brought about one of the coldest years on record and caused crop failure in many parts of the world. The initial CAMP pulse was hundreds of times larger, they say.
Sediments just below the CAMP layer contain fossils from the Triassic period. There are large terrestrial and semi-aquatic relatives of crocodiles, strange tree lizards, giant, flat amphibians and many tropical plants. It then disappears with a CAMP eruption. Tiny feathered dinosaurs existed tens of millions of years before this, survived, and eventually thrived alongside turtles, true lizards, and mammals and grew much larger. Perhaps because they are small and able to survive in burrows.
“The scale of the environmental impact is related to how concentrated the event is,” said the study co-authors. paul olsonLamont-Doherty paleontologist. “Small events spread. [tens of thousands of years] It has a much smaller impact than the total amount of volcanic activity concentrated within 100 years. “The most important implication is that the CAMP lavas represent an extremely concentrated event.”
The study was co-authored by Huapei Wang of the China University of Geosciences, Morgan Schaller of Rensselaer Polytechnic Institute, and Mohammed Et-Touhami of the University of Morocco’s Mohamed Premier.
