The Triassic Period, about 252 to 201 million years ago, was a time of volatile change, particularly during an interval known as the Carnian (about 237 to 227 million years ago). Three dramatic events occurred on Earth: the first dinosaurs appeared, gigantic volcanic eruptions called the Wrangellia large igneous province spewed out greenhouse gasses and the climate suddenly shifted to warmer, more humid conditions that scientists call the Carnian Pluvial Episode (CPE).
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Source: Phys.org