Vermeulen describes the Chinese study sites as “something of a geologic perfect storm” when it comes to coal use. This is the only known area in the world where people burn coal from the Permian-Triassic boundary, he explains. Because the local coal’s silica content is so high, its carbon and volatile content is relatively low, so people must burn more of it to produce adequate heat.14 Image: © Jules Bucher/Science Source.