Why a Wildfire Can Keep Burning After the Flames Are Gone

The dramatic flames from July's huge Cairngorms wildfire are gone, but hot spots can keep burning beneath the earth. That is the odd problem drones are being used to hunt: a fire that has left the visible surface but hasn't stopped smoldering underground. The appeal of an airborne search is obvious — a hotspot under the soil isn't something you spot from a footpath, and it can persist after the blaze looks finished. What the surface shows and what the ground is doing are two different things.