Triassic Period ended with a ‘lost’ mass extinction
Before the dawn of the age of dinosaurs, a heavy rain descended upon the supercontinent Pangaea, and it kept raining for more than a million years.
This epic rainy spell, known now as the Carnian Pluvial Episode (CPE), occurred roughly 233 million years ago and was a stark shift from the typically arid conditions of the late Triassic Period. But storms weren’t the only change Earth was facing. Recent fossil evidence suggests the CPE was a major extinction event, driven by volcanic eruptions and climate change, that resulted in the deaths of one-third of all marine species, plus a significant number of plants and animals.
This ‘lost’ extinction event doesn’t quite reach the death toll of the five major mass extinctions typically discussed by the scientific community – the PermianTriassic extinction event, which occurred just 20 million years earlier, may have wiped out 90 per cent of living species, for example. However, the CPE isn’t just important for what was lost, but also for what was gained. Far from just a period of death, the CPE was a period of ‘turnover’, effectively paving the way for the dominion of the dinosaurs and the evolution of many terrestrial animal groups that still roam Earth today.
“A key feature of the CPE is that extinction was very rapidly followed by a big radiation [of new species],” said Jacopo Dal Corso, a geology professor at the China University of Geosciences in Wuhan. “A number of groups that have a central role in today’s ecosystems appeared or diversified for the first time in the Carnian [an age within the Triassic that lasted from 237 to 227 million years ago].”
Those groups include modern coral reefs and plankton in the oceans, as well as the appearance of land-based fauna such as frogs, lizards, crocodilians, turtles and a diverse new swath of dinosaurs, who would thrive for the next 150 million years. Conifers also made their first appearance during the Carnian, further planting the roots of many modern ecosystems and inviting the ‘dawn of the modern world’.
But what brought on the world-changing rain in the first place? It’s hard to say for certain, but the authors of a new study believe the answers may lie in a continentspanning lava field known as the
Wrangellia Terrane, which runs for thousands of miles across the western coast of modern-day Canada. This massive igneous province was laid down by violent volcanism during the Carnian, and overlaps, at least partially, with the CPE.
Prior studies estimate that those mighty eruptions released at least 5,000 gigatonnes of carbon into the atmosphere – that’s hundreds of times more than annual global emissions today – likely kicking off the extreme climate change that followed. The world became significantly more humid, heavy rains became the norm, the oceans acidified and entire species died in droves, paving the way for strange new plants and animals to slowly take over. However, much more work is needed to understand the full scope of the CPE and its possible triggers. BRANDON SPECKTOR