TLDR: Triassic rain shift due to volcanic eruptions leads to dinosaurs’ dominance after altering Earth’s climate and fauna.
This article is a summary of a You Tube video “That Time It Rained for Two Million Years” by PBS Eons
Key Takeaways:
- Triassic Period Setting: Earth 250 million years ago was hot, flat, and dry due to a supercontinent called Pangea, with dominant early reptiles and mammal ancestors.
- Carnian Pluvial Episode (CPE): Around 234 million years ago, the climate shifted, leading to intense, continuous rain for about two million years.
- Impact on Fauna: The prolonged rain resulted in the decline of many early reptiles, paving the way for the rise of dinosaurs.
- Geological Evidence: Rocks from the early Triassic are mostly red sandstones and dry soil deposits, with no coal swamps, indicating a hot, dry climate.
- Pangea’s Influence: The shape of Pangea hindered rain cloud movement and lacked mountain ranges, contributing to the arid climate.
- Pre-CPE Fauna: Dominant creatures included crurotarsans (croc-like reptiles), rhynchosaurs (herbivores with parrot-like beaks), and dicynodonts (mammal-like reptiles).
- Discovery of CPE: In the 1990s, geologists discovered rocks indicating massive rainfall globally during the Carnian age within the Triassic.
- Dinosaurs’ Rise: Before the CPE, dinosaurs made up about 5% of terrestrial vertebrate fossils; after, they accounted for over 90%.
- Role of Vegetation: The rain led to a proliferation of large conifers and coal-forming plants, altering the food supply and favoring dinosaurs over other species.
- Cause and End of CPE: The CPE was likely triggered by the Wrangellian eruptions in Alaska and British Columbia, and ended as the planet stabilized CO2 levels, returning to a hot, dry climate.
