The Rise Of The Dinosaurs 200 Million Years Ago Was Caused By Volcanic Winters, Not Warmth
One of the five greatest mass extinctions took place on Earth about 201.6 million years ago, when three-quarters of all living species disappeared.
The event occurred at the same time as powerful volcanic eruptions that split the giant continent of Pangaea apart. Over the course of around 600,000 years, millions of cubic miles of lava spewed into the atmosphere.
It marked the end of the Triassic period and the beginning of the Jurassic period, which was when dinosaurs arose and took over the planet.
The exact causes behind the End Triassic Extinction have been debated for years. The most popular theory is that carbon dioxide from the eruptions accumulated over many millennia, leading to the planet’s warming and ocean acidification, which made life unsustainable for many creatures.
However, a new study has suggested that the main driver behind the mass extinction event was cold, not warmth. Evidence shows that the volcanic eruptions lasted only decades rather than a hundred thousand years.
During this much shorter timeframe, sulfate particles that reflected sunlight were released into the atmosphere, blocking most of the sun, cooling the planet, and freezing many living creatures.
Later on, the temperatures gradually rose and likely contributed to the mass extinction, along with increased levels of atmospheric carbon dioxide. However, according to the researchers, the volcanic winters were the most damaging to Earth’s inhabitants.
“Carbon dioxide and sulfates act not just in opposite ways, but opposite time frames,” said Dennis Kent, the lead author of the study from Columbia Climate School’s Lamont-Doherty Earth Observatory.
“It takes a long time for carbon dioxide to build up and heat things, but the effect of sulfates is pretty much instant. It brings us into the realm of what humans can grasp. These events happened in the span of a lifetime.”
herraez – stock.adobe.com – illustrative purposes only – pictured above is a Tyrannosaurus rex skeleton on a black background
The Triassic-Jurassic extinction has also been linked to the eruptions of the Central Atlantic Magmatic Province (CAMP), a large area made up of magma rock.
Archaeologists have uncovered fossils of tree lizards and flat-headed amphibians from the Triassic period beneath the layers of lava.
In previous work at CAMP, Kent and colleagues identified a consistent reversal of polarity in rock sediments just below the initial eruptions.
They all happened simultaneously in what are now different parts of the world. Then, radioactive isotopes were used to date the start of volcanism to about 201,564,000 years ago.
In the new study, the team compared data from CAMP rock layers in the mountains of Morocco, in Nova Scotia’s Bay of Fundy, and in New Jersey’s Newark Basin.
They found five lava eruptions scattered throughout 40,000 years, each with magnetic particles aligned in one direction. This indicated that the eruptions emerged in less than 100 years.
“Small events spread out over [tens of thousands of years] produce much less of an effect than the same total volume of volcanism concentrated in less than a century. The overarching implication is that the CAMP lavas represent extraordinarily concentrated events.”
The study was published in the Proceedings of the National Academy of Sciences.
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