The weather couldn’t stay calm and cool forever, and oil sands facilities in northern Alberta, north of Fort McMurray, were evacuated late yesterday as the fire expanded in their direction at almost a walking pace. The fire threat helped support oil prices, though other factors are pushing prices lower at this hour. One of the open questions is whether it is possible for oil sands to burn in a wildfire. Physicists tell me they could in theory but probably not in practice. Oil sands don’t support the kind of plant growth that would sustain a hot fire, and the sand itself suppresses air flow.