In the center of the arid and ancient supercontinent Pangaea, thousands of miles from the sea, time-traveling aliens returned to witness a pivotal moment in Earth’s history. As they arrived, the rain began to fall. Just off Pangaea’s west coast, in what is now Canada, epoch-ending volcanic activity triggered a chain of events making this relentless downpour inevitable. The landscape would never look the same again, for this marked the beginning of a rainstorm lasting over a million years, a rainstorm that would change the course of life on Earth forever. This prolonged rainfall allowed dinosaurs to rise to dominance in an extraordinary evolutionary coup.
What makes this event even more surprising is that the type of catastrophe responsible for this rain is typically the most reliable and devastating extinction event Earth has ever known. But this event was different, taking the butterfly effect to its extreme. If a butterfly flapping its wings can lead to a tornado a thousand miles away, imagine the consequences of a volcanic eruption 100 times larger than a Supervolcano.
Pangaea was the largest landmass ever to exist, combining all modern continents into one supercontinent. Its vast size meant that the interior was far removed from coastal climates, receiving minimal rainfall and favoring species adapted to arid conditions. During the dry Carboniferous period around 300 million years ago, key species like dragonflies, millipedes, and spiders emerged. Notably, the diapsids, a group including lizards, snakes, and archosaurs—crocodiles, birds, and eventually dinosaurs—also flourished during this time.
Despite the extreme conditions on ancient Earth, volcanic activity posed the greatest threat. Earth's thin crust, comparable to a single page in a book representing the entire planet, rests above molten magma rising from the core. Occasionally, massive plumes of magma break through the crust, creating flood basalt eruptions capable of lasting over a million years. These eruptions are linked to the planet’s most significant extinction events, including "The Great Dying," where ocean temperatures soared to 40 degrees Celsius. Yet the Wrangellian eruption, the catalyst for the million-year rainstorm known as the Carnian Pluvial Episode, was unique.
Unlike previous mass extinctions, this event triggered a profound ecological transformation rather than total collapse. Volcanic activity from the Wrangellian Large Igneous Province released enough greenhouse gases to supercharge Earth’s water cycle. Carbon dioxide levels exceeded 1000 ppm, causing a temperature rise of 3-4ºC. The increased heat accelerated evaporation and cloud formation, spreading rainfall deep into Pangaea’s arid interior.
However, this transformation came at a cost. Species adapted to dry conditions faced environmental stress, while acid rain, driven by volcanic emissions of sulfur dioxide and hydrogen sulfide, further impacted ecosystems. The acidic downpours eroded rocks and soils, reshaping the landscape and creating new cave systems like those in Britain’s Triassic limestone formations. Oceanic life was particularly affected, with many regions becoming anoxic and acidified, causing the extinction of species like conodonts, ammonoids, and reef builders while plankton such as dinoflagellates thrived.
Amid this upheaval, one species began to flourish: Herrerasaurus. This early dinosaur, reaching 6 meters in length and weighing over 300 kg, thrived in the volcanic floodplains of South America. As the rains expanded habitable regions, the Herrerasaurus and similar species took advantage of newly opened niches, setting the stage for dinosaur dominance. Fossilized footprints from this period, especially in the Dolomites, show a rapid shift from diverse species to dinosaur ecological dominance, with over 90% of preserved tracks belonging to dinosaurs.
Over the 2 million years of the Carnian Pluvial Episode, the Earth's climate underwent significant changes, with four major rain pulses reshaping the planet. When the Wrangellian eruption finally subsided, greenhouse gas emissions decreased, and flora absorbed atmospheric carbon, stabilizing the climate. However, the event left an indelible mark, fundamentally altering ecosystems and paving the way for dinosaur supremacy.
The aliens departed, having witnessed the dawn of dinosaur dominance and a remade Earth. Yet, 180 million years later, another extinction event would end the dinosaurs' reign, shifting dominance to mammals, including humans. These moments serve as profound reminders of how life constantly evolves in response to Earth’s shifting conditions, adapting with each challenge it faces.