A massive volcanic eruption 234 million years ago triggered a global, rain-soaked climate crisis.
In short: The Carnian pluvial episode was a million-year climate shift that transformed Earth from an arid landscape into a humid, rain-drenched world. Driven by colossal volcanic activity, this ancient event reshaped the oceans, triggered mass extinctions, and inadvertently cleared the stage for the rise of the dinosaurs and modern flora.
Around 234 million years ago, the eruption of the Wrangellia Large Igneous Province off the coast of North America released massive quantities of volcanic CO2 into the atmosphere. This triggered global warming of at least 3–4 °C, accelerating the hydrological cycle and causing a significant increase in rainfall. The resulting humid conditions interrupted the otherwise arid climate of the Late Triassic, leading to increased continental weathering and the influx of mud and silt into marine basins.
The environmental upheaval caused by this climate shift was profound. In the oceans, the increased runoff and potential acidification disrupted carbonate platforms, causing a decline in carbonate-secreting microbes and a shift toward animal-dominated ecosystems. While many aquatic invertebrates, such as ammonoids and crinoids, suffered high extinction rates, the episode fostered new life. It coincided with the rapid diversification of scleractinian corals, the first appearance of modern microplankton, and the expansion of conifers and ferns.
On land, the episode is often cited as a catalyst for the rise of dinosaurs, though the relationship remains debated. While dinosaur abundance increased during this humid phase, some evidence suggests their diversification was already underway. More clearly, the event forced a turnover in herbivorous tetrapods, favoring specialized groups like hyperodapedontines before they eventually vanished. The episode also left behind the oldest widespread amber deposits, which preserve early glimpses of ancient arthropods and microorganisms.
The scientific understanding of this event has evolved significantly since Michael J. Simms and Alastair H. Ruffell first proposed the hypothesis in 1989. Initially met with skepticism, the theory gained traction as researchers identified geochemical signatures—such as mercury spikes and carbon isotope excursions—that link the climate disturbance directly to the Wrangellia volcanic pulses. Today, the Carnian pluvial episode serves as a critical case study for understanding how massive volcanic events can force rapid, global-scale changes in Earth's climate and biological systems.
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- Summary by Intellect · source: Carnian pluvial episode
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