Earth once experienced a rainstorm that lasted for two million years

Around 230 million years ago, the planet was a giant, arid desert known as Pangea. Then, a series of massive volcanic eruptions in what is now Canada released enough carbon dioxide to trigger a runaway greenhouse effect. The oceans heated up, the water cycle went into overdrive, and the skies opened up.

Geologists call this the Carnian Pluvial Event. They found the evidence in layers of ancient rock across the globe, where dry red silt suddenly gives way to thick gray mud and river sediment. This wasn't a seasonal monsoon. It was a relentless, multi-millennial deluge that permanently altered the chemistry of the oceans and the landscape of the continents.

This epic rainstorm was actually the turning point for life on Earth. Most of the dominant species of the time couldn't handle the humidity and died off. In the vacuum they left behind, early dinosaurs—who had been minor players until then—evolved rapidly to fill the space. We literally owe the age of the dinosaurs to the longest bad weather streak in history.