The Carnian Pluvial Event

A 2-Million-Year Period of Rain that Shaped Earth's History

Image of ancient Earth with lightening and rain
Image of ancient Earth with lightening and rain
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We enter the field of geology today. There is no doubt that Earth’s history has been marked by several intriguing and exciting events that have shaped life on our planet. These events have led to the emergence of new life or the complete annhilation of certain species. One such remarkable occurrence was the Carnian pluvial event (CPE), also known as the Carnian crisis, which took place around 232 million years ago. This was a period of continuous rain that lasted 1-2 million years, and played a pivotal role in the evolution of life on Earth, particularly during the emergence of dinosaurs and other terrestrial fauna.

Unveiling Ancient Mysteries

Around 200-300 million years ago, the Earth was home to a supercontinent known as Pangaea, when it experienced an unprecedented era of non-stop rainfall. The Earth, and its supercontinent were prone to monsoons at this time. Monsoons are periods of heavy rain when moisture-heavy air rises from the sea towards land. Once there, it cools down and falls as heavy rain. During the Carnian pluvial event, the seas heated further, resulting in more moisture above, and heavier rainfall on land.

Pangaea separation

Pangaea separation animation

 

Geologists in the 1970s and 80s made significant discoveries in ancient rocks dating back to 232-4 million years. Studies conducted in the eastern Alps and the UK revealed layers of siliclastic sedimentation and gray rock, indicating a transition from a dry spell to a prolonged rainy period.

Subdivision of the Triassic according to the ICS, as of 2021

Subdivision of the Triassic according to the ICS, as of 2021

The Trigger for Dinosaur Dominance

It is thought that the Carnian pluvial event was triggered by a surge in humidity, possibly due to a massive volcanic eruption in the Wrangellia Large Igneous Province. This event led to a substantial increase in global temperatures, warming oceans, and elevating atmospheric moisture content. Research published in the Journal of the Geological Society highlighted how this wet period was advantageous for dinosaurs, allowing them to diversify and dominate the land.

“The eruptions peaked in the Carnian,” Jacopo Dal Corso, involved in research into the eruption, told Everything Dinosaur. “I was studying the geochemical signature of the eruptions a few years ago and identified some massive effects on the atmosphere worldwide. The eruptions were so huge, they pumped vast amounts of greenhouse gases like carbon dioxide and there were spikes of global warming”.

Impact on Evolution

This prolonged humid and wet period was not conducive to life according to the study in the Journal of the Geological Society: “volcanic eruptions generate acid rain and greenhouse gases, which in turn lead to extinctions by shock warming, stripping of vegetation and soils on land, and ocean anoxia and acidification”.

Conversely though, this period of rain benefited dinosaurs and also facilitated the diversification of various terrestrial fauna. It played a crucial role in shaping the modern fauna of terrestrial tetrapods, including turtles, crocodiles, lizards, and mammals. This era marked a significant turning point in Earth’s history, enabling the rise of dominant land-dwelling species following a tumultuous period characterised by volcanic activity and extinctions.

“In the wake of wide extinctions of plants and key herbivores on land, the dinosaurs were seemingly the main beneficiaries in the time of recovery, expanding rapidly in diversity, ecological impact (relative abundance) and regional distribution, from South America initially, to all continents,” one team wrote in their paper.

“It may have been one of the most important [rapid events] in the history of life in terms of its role in allowing not only the ‘age of dinosaurs’, but also the origins of most key clades that form the modern fauna of terrestrial tetrapods, namely the lissamphibians, turtles, crocodiles, lizards and mammals.”

There is no doubt that the Carnian pluvial event is an example of how changes in our planet’s environment can drive evolutionary changes and shape the course of life on our planet. This ancient rainy period not only nurtured the rise of dinosaurs but also laid the foundation for the diverse terrestrial fauna that we see today.

I am a Chartered Environmentalist from the Royal Society for the Environment, UK and co-owner of DoLocal Digital Marketing Agency Ltd, with a Master of Environmental Management from Yale University, an MBA in Finance, and a Bachelor of Science in Physics and Mathematics. I am passionate about science, history and environment and love to create content on these topics.