Bits of charcoal entombed in ancient rocks unearthed in Wales and Poland push back the earliest evidence for wildfires to about 430 million years ago. Besides breaking the previous record by about 10 million years, the finds help pin down how much of Earth's atmosphere was oxygen at the time: at least 16 percent, researchers report June 13 in Geology. That conclusion is based on lab tests that show how much oxygen it takes for a wildfire to take hold and spread.
展开▼
