Sulphur flows at Lastarria volcano in the North Chilean Andes

Abstract

Although several authors have suggested that sulphur plays an important role in the volcanism on the jovian moon Io^1–8, some deny the participation of elemental sulphur there, at least in the form of cooled flows⁹. Studies of volcanism on Io have focused attention on the role of sulphur in terrestrial volcanism. On Earth, fumarolic sulphur is very common in almost all active volcanoes, but sulphur flows are rare, having been reported only on Siretoko–Iôsan volcano in Japan¹⁰, on Sierra Negra and Azufre volcanoes in the Galápagos Islands^11,12 and on Mauna Loa in Hawaii^13,14. Of these, the Siretoko–Iôsan example is the only natural molten sulphur flow to have been observed in the process of formation; the others being rather poorly exposed. I describe here a singularly well-exposed example of sulphur lava flows, on Lastarria volcano in Chile, where the liquid sulphur appears to have been formed by melting of fumarolic sulphur deposits caused by a rise in the thermal gradient owing to the renewed activity of the magmatic source.