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Have you ever thought, ”What if it had rained for a year non-stop?”. In the past, a similar event has taken place, but instead of one year, for about 1-2 million years, there was a prolonged humid interval with multiple wet pulses and increased rainfall. This was the Carnian Pluvial Episode (CPE), often called the Carnian Pluvial event. It was an extraordinary climatic event that took place about 233 million years ago. The CPE signifies a pivotal yet largely unrecognised moment in Earth’s history; an era of drastic climate shifts that obliterated ancient ecosystems while concurrently paving the way for the contemporary world.

How it started

During the Late Triassic Period, when the supercontinent Pangea still existed, over 1000000 km³ of flood basalts erupted over the course of multiple phases (A flood basalt is an extensive lava flow that covers large areas of land or ocean floor with layers of basalt lava, forming vast volcanic provinces). These eruption phases largely occurred in the Wrangellia Large Igneous Province, a massive volcanic region that was likely an oceanic plateau or island arc situated farther south in the oceans. It later collided and accreted onto the North American continent, forming parts of modern Alaska, British Columbia, and Yukon.

Because of all these eruptions, massive amounts of CO₂ gas were pumped into the atmosphere, with the release of Methane hydrate. All these greenhouse gases trapped the Sun’s heat within the planet’s atmosphere, resulting in the rapid rise in global temperatures. This greenhouse effect intensified over hundreds of thousands of years as gas buildup continued, leading to the intensification of the hydrologic cycle (Pre-CPE Earth was already roughly 6–10°C warmer than today, and after CPE, the temperatures rose about 3-8°C depending on region to region).

During the episode

As the continent of Pangea was one big island (sort of), the regions in the centre received very little rainfall. A real-life example of this situation is Australia. In the extremely arid mainland, species of Archosaurs (early relatives of crocodiles, etc), hardy reptiles, etc., flourished. In the initial phases, the interior of Pangea may have gotten even drier, but during the CPE, the dry, desert-like lands of Pangea were transformed into a humid, tropical world that lasted for about one to two million years. Many species that had adapted to the arid conditions could not survive the sudden climatic shift, leading to widespread extinctions among reptiles, amphibians, and several marine organisms. Heavy and continuous rainfall caused soil erosion and nutrient runoff, enriching lakes and shallow seas and triggering major ecological changes. The Carnian period, though initially started as an extinction event, later proved to be a major driving factor for the evolution of dinosaurs and some modern-day ecosystems. Once the rainfall increased, new habitats such as wetlands, rivers, and dense forests began to spread across areas that were once barren. After the CPE, dinosaurs rapidly diversified and rose to dominance, filling the ecological gaps left by the vanished species. Small, early mammals also appeared and began to evolve under these new, wetter conditions. Humid-loving plants like conifers and ferns flourished, forming the first large forest ecosystems of the Mesozoic Era.

The rise in CO₂ due to all the eruptions during the CPE likely caused a drop in ocean pH, leading to its acidification and a collapse in marine biodiversity. This caused a quarter to a third of marine genera to go extinct ( Somewhere around 33%). Sea Lilly population saw devastation greater than any before. On land, however, life saw great changes, such as the shift from arid-loving ecosystems to ones that were humid-loving. Conifers and Fern species absolutely flourished, leading to an increase in resin production. The Dino population skyrocketed, shifting from almost absent to being the majority species on land (about 80%). Several other modern-day prevalent species, such as Crocodiles, lizards, diversified. Our own ancestors, early mammals, also originated in this age. It was not all rainbows and sunshine, though, as many species on land also went extinct. Rhynchosaurs, Dicynodonts (dominant herbivores and herbivorous mammal relatives respectively) all were nearly wiped out.

Why did the Dinosaurs rise?

Dinosaurs first appeared around 245 million years ago. So you would ask yourself, “Why did the Dinosaurs suddenly flourish after the CPE?”. This was because after about 10M years, Pangea’s environment saw dramatic changes in its ecosystems. Fossil evidence from the Southern Alps (Italy), the Germanic Basin (Europe), and Argentina shows the first ever widespread Dinosaur footprints and bones appearing synchronously across Pangea. The near-extinction of the herbivores Rhynchosaurs and Dicynodonts killed off the competition for our favourite prehistoric species. Also, the new and massive population of Ferns and conifers   heavily boosted the dinosaur population as they were the ideal food source for the early herbivorous dinosaurs. The CPE didn’t just hand it to the Dinos to become dominant; in fact Dinos were the fastest to adapt to CPE. Which was the biggest reason for their rise!

The Dawn of the New World

The CPE didn’t just change species and ecosystems; it changed everything. The Pre-CPE era was ruled by primitive species and had an ‘ancient-style’ to them, but now, a ‘modern-style’ of ecosystems had come to rise, and many species have come to be that are ancestors of the modern world. This age was also when the blueprint of modern forests began, as they started to look more alike to the ones we have now. In the oceans, reef systems slowly developed. From the rise of forests to the reign of dinosaurs and the birth of coral reefs, the CPE set the stage for the next 200 million years of life on Earth.

Timeline of the major events

Conclusion

The Carnian Pluvial Episode shows how a few million years can rewrite life on Earth. What happened during the CPE, isn’t just ancient history, it is he blueprints for modern life! If not for the CPE, it is very much possible that us humans may not even have existed at all! While many species went extinct, it allowed for new species to form and many others to adapt. The CPE teaches us that climate change doesn’t just change the temperature or weather patters, it reshapes life itself. It could be said that this is one of the biggest butterfly effects of all time, who knew that some volcanic eruptions could reshape life on our blue ball forever.