In places such as the Pacific Northwest, it seems like it's always raining. But did you know there was a time on Earth were rain poured for over a million years? This episode is known as the Carnian pluvial event (CPE). Thought to have been triggered by unique, volatile conditions, it took place about 232 million years ago—changing the natural landscape forever.
The Carnian pluvial episode lasted one to two million years, bringing one of Earth’s dry spells to an end. It marked a dramatic shift from the arid conditions of the late Triassic period. During this time, all continents were still together as Pangea, which was already prone to monsoons due to its geographical conditions. Sea temperatures were high, and humid ocean air blew inland, cooling and precipitating as heavy rain.
On top of these conditions, scientists have suggested this million-year monsoon could have been triggered by a series of massive volcanic eruptions that took place on the Wrangellia Large Igneous Province, located in what today is Alaska and British Columbia. Volcanic eruptions have been observed to affect the levels of water vapor in the stratosphere, although the opposite has been studied too—that is, intense rainfall resulting in a volcanic eruption.
The Carnian crisis was first studied in the UK by geologists Alastair Ruffell and Michael Simms when the latter noticed something peculiar about the red stone of Somerset’s Lipe Hill. A stripe of grey running through rocks in the area indicated that it had suddenly gone from a period of severe drought to intense humidity. Further evidence was found throughout the late 20th century in places such as the Alps, sparking questions about how this weather episode affected existing life on Earth.
As environments around the world drastically changed, the Carnian pluvial event is regarded as a period of increased extinction. With an increase in humidity and the oceans becoming more acidic, one-third of all marine species, plus a large amount of plants and animals, were wiped out.
However, the Carnian wet episode also opened the door for the flourishing of new life, such as dinosaurs, frogs, lizards, and turtles, as well as modern coral reefs and plankton in the oceans, according to geology professor Jacopo Dal Corso, who published a study on the topic. “A key feature of the CPE is that extinction was very rapidly followed by a big radiation [of new species],” he told Eos.org. “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].”
While it can be hard to grasp the wild conditions that plagued the Earth before the dawn of civilization or the way long-term conditions shape the way flora and fauna evolve, studying episodes such as the Carnian pluvial event can help scientists better understand the past and the future of our planet.
Did you know there was a time on Earth when rain poured for over a million years?
Known as the Carnian pluvial event, it changed the natural landscape forever.
It opened the door for the flourishing of new life, such as dinosaurs, frogs, lizards, and turtles, as well as modern coral reefs and plankton in the oceans.
Source: Extinction and dawn of the modern world in the Carnian (Late Triassic)
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