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The relationship between dinosaurs and volcanoes has not always seemed so lovable.
For decades, scientists have wondered whether volcanoes or an asteroid caused the dinosaurs to suddenly become extinct around 65 million years ago. It wasn’t until 2010 that an international panel of experts officially declared that it was space rock, and not giant eruptions, that was the main cause of the dinosaurs’ disappearance.
And now, a team of researchers are presenting the most compelling evidence to date that massive volcanic events likely helped dinosaurs conquer the planet, at least in another era. Their results were published Monday in the Proceedings of the National Academy of Sciences.
The Triassic Period, which began around 250 million years ago, was a time of massive ecological change following the largest mass extinction on record. While dinosaurs had appeared around this time, they were different: leaner, more reptilian, less box office success that we flock to theaters to see. But it was during this period that the dinosaurs diversified to become wonderful beasts like the Tyrannosaurus rex or the Triceratops which dominated the ecosystems of the entire planet Earth until the end of the Cretaceous period.
To understand what led to this transformation of the dinosaurs, scientists looked at a phase spanning two million years during the Triassic Period known as the Carnian Rainfall, or CPE. During this episode, 234 million to 232 million years ago, the planet experienced an increase in global temperature, humidity and precipitation – a climate often referred to as “mega-monsoon.”
The researchers analyzed the sediments and plant fossils of a lake in northern China and were able to match four intense phases of volcanic activity with changes in the Carnian rainfall event.
Previously, the researchers speculated that the changes in the global carbon cycle during the episode were the result of major volcanic eruptions from what is now a mass of igneous rock found throughout western L ‘North America. The new study links the timing of the episode with four distinct peaks of mercury – a well-established indicator of volcanic activity – to changes in the carbon cycle as well as precipitation, which resulted in local changes in vegetation on earth and in the lake.
“We are often able to link volcanism to global warming, but our study is unusual in that we have also linked it to periods of intense rainfall,” said Jason Hilton, paleobotanist at the University of Birmingham in England and co-author. “With each pulse of volcanism, we see an increase in plants adapted to humid and aquatic environments.”
Jing Lu, a researcher at the Chinese University of Mining and Technology and also a co-author of the study, added that these eruptions “were powerful enough to trigger evolutionary processes during the Triassic.”
During the episode, plant species that could not adapt to the wetter environment became extinct, as did a number of animal species, from the large reptilian herbivores on earth to small gastropods in the ‘water. “These changes have freed up ecological space for other groups of organisms, such as dinosaurs, to thrive,” said Dr. Hilton.
In addition to the diversification of dinosaurs, researchers believe that the Carnian rainfall event laid the foundation for today’s ecosystems.
“During the CPE, we start to see this perfect mix of prehistoric monsters as well as modern mammals and reptiles,” said Emma Dunne, a researcher at the University of Birmingham who was not involved in the study but whose the work is focused on the drivers of diversification of ancient tetrapods like dinosaurs. “You had turtles, but also pterosaurs. “
This new evidence is leading researchers to think more about our rapidly changing climate.
“The magnitude of these eruptions eclipses all volcanic eruptions in human history,” says Sarah Greene, study co-author and paleoclimatologist at the University of Birmingham. “But the rate at which these eruptions emit carbon dioxide is tiny compared to human carbon dioxide emissions today.”
Dr Dunne echoed that thought. “Those two million years were a blink of an eye in geological time, so to think that we are changing the planet at an even faster rate than humans is a little scary,” she said. “Who knows what we’re going to talk about.”
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