Hot oceans, impressive volcanic activity, an atmosphere saturated with carbon dioxide, and Pangea turned into a giant desert. The prehistoric world would not have been friendly to humans, but as Dr. Malcolm says, life finds a way, and so it did back then... even under rain that on average lasted two million years. Experts call the incident "Carnian Pluvial Event", it happened about 234 million years ago, and triggered the rise of the dinosaurs as we know them.
Our story begins in the Triassic period, a fraction of the Mesozoic era that began 252 million years ago and ended about 50 million years later. The world was warm and dry, to such a point that its effects can be seen in red strata. Technically dinosaurs already existed, but they were far from being a dominant force, and had to compete with other reptiles and some mammal-like creatures, among which stand out the first crurotarsans (carnivores), rhynchosaurs (herbivores, easy to recognize thanks to their striking beak), and dicynodonts, with extremely abundant genera. But among the red marks of the Triassic, experts found evidence of boulders, sediments of giant lakes, and swamps, signs that suggest enormous precipitation, not only in size, but also in time... two million years, to be more precise.
The Carnian Pluvial Event
During the following years (the first study was published in 1989), new discoveries confirmed the event, which occurred between 234 and 232 million years ago. Finally, it was identified as the Carnian Pluvial Event, in reference to the Carnian age (235-228 Ma) over which it occurred. How much rain are we talking about? Data suggests an annual average of 1,400 millimeters (three times the average precipitation of Madrid) ... repeating over and over, across the planet, for two million years. In other words, the Carnian Pluvial Event was not a global hyperstorm, but rather a frequent series of rains and floods. And from that point, the presence of dinosaurs exploded. At the beginning of the Pluvial Event, their fossils represented 5 percent of terrestrial vertebrates. When it ended, the percentage exceeded 90 percent. Why? We still don't know for sure, but the strongest hypothesis points not to the water, but to what it brought: gigantic and abundant vegetation.
Rhynchosaurs and dicynodonts did not fully take advantage of this new food source, while the coprolites of some herbivorous dinosaurs reveal up to 85 percent fiber (in other words, they ate wood and leaves). Now, the question of the two million: Why did it start raining? Massive volcanic activity (which lasted five million years), combined with constant emission of carbon dioxide, rising temperatures (between 3 and 10 degrees Celsius), and the subsequent acceleration of the hydrological cycle. The atmosphere became so warm and humid that rain touched every corner of Pangea. Over time, the world absorbed the excess CO2, and the Carnian Pluvial Event ended, giving rise to the "age of the dinosaurs".
