In the Smoking Hills area of the Canadian Arctic coast active areas of fire-baked rock or "bocannes" occur in Cretaceous mudstones along sea cliffs and in areas of recent slumping. Extinct and active bocannes are marked by bleaching, baking, and reddening of otherwise dark mudstones. Active bocannes are characterized by fumes of hot sulfurous gas and high ground temperatures. Petrographic, mineralogical, chemical, and calorific analyses indicate that the bocannes are fueled by oxidation of pyrite and (or) organic matter. With heating of the strata by oxidation, combustible gases are driven off that may burn in restricted areas, resulting in localized melting of the strata. The zone of active bocannes is restricted to areas of glacially(?) disturbed strata and landslides, indicating that disruption, rapid exposure, and access to atmospheric oxygen are required to generate the high temperatures. Spontaneous combustion of the exposed strata is facilitated by the very fine particle size and thus large surface area of pyrite, which is framboidal, and organic matter.