The National Park Service now knows what started the Dome Fire, entering a third week of burning in the backwoods near the southern entrance of Yosemite in Maripiosa County.

The Dome Fire has been burning slowly through Yosemite National Park’s backcountry since mid-September, growing to more than 4,250 acres and forcing trail, road (and airport) closures near the park’s southern entrance in Maripsoa County.