Cracking the Code of the Late Triassic's Super Long Rainy Season:
Imagine enduring the longest rainy season you've ever experienced—like those epic tales of Noah and his ark. Now, journey back over 234 million years ago to the late Triassic period. Picture a world that's not just rainy, but scorching hot and incredibly steamy, with rain pouring down relentlessly for an unimaginable two million years straight. You'd need more than just one umbrella - you'd need a whole fleet of them, maybe even some advanced waterproof technology!
During the Triassic period, Earth underwent some colossal changes in its climate, landscapes, and the types of life inhabiting it. One of these major but lesser-known events was the Carnian Pluvial Event (CPE). It's no surprise that two million years of non-stop rain would have a monumental impact, forever reshaping the planet and leaving behind clues for us to decipher.
Life Before the Never-Ending Rain:
Let's take a look into past before it was saturate in endless rain. Imagine a time when all the continent were nestled together in a gigantic landmass known as Pangea. But don't expect lush greenery instead picture an immense dehydrated desert stretching from the icy North Pole to the sunny South Pole. Plant life was pretty basic with small desert plants struggling to survive in the sandy terrain.
Back then, rainy seasons were rare treats, brief and infrequent. The towering mountains at the heart of Pangea blocked most of the rain, leaving only the coastlines to enjoy regular showers. Earth was much toastier than it is today, with temperatures about 10 degrees Celsius higher, and the seas were like warm bathwater at a scorching 47 degrees Celsius
As for the critters, think ancient insects, reptiles, mammals, and the first dinosaur rookies. Reptiles were the kings of the land, strutting their stuff while the dinosaurs were just starting to make their debut, though the climate wasn't exactly ideal for them. Earth's main ocean Panthalassa was a bustling hub of life hosting creatures like ammonoids gastropods sponges and corals.
Then out of nowhere what began as a few dark clouds and a sprinkle of rain turned into a monumental two million year long monsoon.
Oddly enough, this epic event stayed under the radar for a while, despite evidence of it popping up since the 1970s. When scientists usually talk about mass extinction events, they focus on the "big five" like those in the Ordovician-Silurian, Devonian, Permian-Triassic, Triassic-Jurassic, and End-Cretaceous periods. But this rainy season phenomenon somehow managed to slip through the cracks.
Some scientists speculate that it got overlooked because it didn't neatly fit into the beginning or end of a major geological era like those other events usually do. It seemed to happen at a pretty random time. But was it really random?
Volcanic Activity in Action:
The leading idea behind this prolonged rainy period is that a series of intense volcanic eruptions in Alaska and British Columbia spewed out massive amounts of carbon dioxide into the atmosphere. This triggered a lengthy phase of global warming and acidification of the oceans. As a result, the air became super humid, leading to extreme rainfall.
These volcanoes were so powerful that they disrupted the natural cycles of water and carbon, permanently altering the Earth's climate. Many species perished as a consequence, including approximately one-third of all marine animals. It's crucial to understand that the rainfall occurred intermittently, rather than in one continuous, never-ending downpour.
"It's akin to charging a colossal battery," explained geoscientist Jacopo Dal Corso, who has spearheaded research into this phenomenon. A substantial cooling effect high up in the atmosphere coupled with extensive evaporation and heating near the surface... will inevitably give rise to an immense storm.
While some paleontologists suggest that the emergence of a new mountain range may have been the culprit, causing pressure changes between land and ocean, most scholars lean towards the volcanism theory as being more plausible.
Unveiling the Clues:
The discovery of the Carnian Pluvial Event didn't happen until the 1970s. While studying rocks in Austria’s Northern Limestone Alps, geologists Schlager and Schollnberger stumbled upon something peculiar: an abrupt layer of dark grey siliciclastic rock sandwiched between the usual carbonate rocks.
Upon dating it, they found it to be approximately 234 million years old. What made this layer intriguing was its inconsistency with the prevailing hot and arid climate of Pangea during that time. Such rock formations typically occur in regions abundant in water, rather than in parched deserts.
Similar rock layers began appearing in various parts of the world. Geologists identified them in southwest England, intertwined with layers of red sandstone. They also surfaced in locations like Israel, Italy, and even Utah in the U.S.
Furthermore, there were other telltale signs of a colossal downpour, including the discovery of amber, coal, ancient riverbeds, and lakes teeming with fossilized plant remains. Additionally, the presence of a white powdery clay known as kaolinite further reinforced the evidence. Moreover, the fossilized pollen and spores found in rocks dating back to the Carnian period provided further indications of a humid climate with scorching temperatures.
Given its relatively recent discovery and the challenges associated with gathering data over the years, some geologists dub the Carnian Pluvial Event as the "hidden extinction."
Life After the Downpour:
While today we fret over human-induced climate change, this ancient period of climate shake-up actually brought about some positive changes for the world. It turbocharged major cycles like carbon and water.
Dinosaurs flourished in this transformed world, and things found a better balance. Reptiles began to dwindle as towering trees and other large plants took over, providing better sustenance for dinosaurs. Alongside them, ancestors of modern animals like turtles and crocodiles emerged. Meanwhile, the oceans, now more acidic, experienced a surge in plankton and the growth of coral reefs.
But did the rain ever cease? Yes, eventually, the ceaseless rain and flooding relented, and global temperatures settled into a cooler, less intense climate. Pangea reverted to a desert, but it appeared altered. The accelerated water cycle caused extensive erosion and transformed the soil from light carbonate to darker, more fertile sediment. The air also transitioned from its previous hot, dry state to a more humid one.
As the Late Triassic period came to an end and the Jurassic period dawned, Pangea began to fracture, giving rise to new oceans. This injected even more moisture into the air, transitioning the climate to subtropical. Deserts transformed into lush tropical forests.
Following the Carnian Pluvial Event (CPE), rainfall began to self-regulate. It fell regularly, averaging 1-3 meters annually, in more consistent, seasonal patterns that didn't persist nearly as long as the two-million-year deluge.
Essentially, this event marked the genesis of our modern world, in geological terms. The environment we inhabit today, the climate, and the diversity of flora and fauna all began to take shape after the CPE.
The Final Thoughts:
Following the Carnian Pluvial Event (CPE), the climate kept on changing, leading to more extinctions and further transformations in the environment. The time of the emergence of dinosaurs and the CPE is no mere coincidence. This event proved crucial for the dominance of dinosaurs during the Late Triassic period.
Scientists are quite content to add another significant mass extinction event to Earth's historical records. While the CPE may not match the scale and violence of the infamous "big five," it nonetheless played a pivotal role in shaping the modern world as we know it today.
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