Vulcano: Crystalline and Molten sulphur
Photos copyright Jürg Alean (JA), Marco Fulle (MF) and Gunter Militzer (GM).
Spectacular fumaroles are Vulcano's speciality. The sulphur needles around this vent are around 2cm long (JA).
Within some fumaroles not only sulphur but also the white mineral gypsum (calcium sulphate) is deposited (JA).
In the fumaroles with the highest temperatures sulphur melts and forms drops resembling amber (MF).
Another drop of molten suphur reflecting the sun: drops have diameters of typically one centimetre (MF).
Starting in 1986 fumarole temperatures rose from about 300°C raising some concern that magma might be intruding at shallow depths beneath Vulcano (MF).
Fumarole temperatures peaked in 1993 when almost 700° C were measured. Later there was a slow decrease of the measured maximum temperatures (MF).
Liquid sulphur sometimes forms miniature flows 20cm or more in length. Note colour differences, cf. next image (MF).
The viscosity of liquid sulphur increases above 200°C due to the formation of polymer chains, and it becomes dark red . These drops are about 3cm long (MF).
Close-up of sulphur crystals in the shape of needles (MF).
Higher magnification shows fractal structure: smaller needles on bigger ones. Condensed drops of water at upper-left (MF).
Here small flows of liquid sulphur form a pond 5cm across (bottom of photo, MF).
Other spectacular drops of liquid sulphur among yellow needles, the largest about 12mm in length (GM).
sulphur needles on the rims around fumarolic vents (MF).
While sulphur crystals near the vent maintain their shape, the ones further from the hot gas (bottom) weather quickly (MF).
Thin layers of Calcium sulphate around the hottest vents of a fumarole (MF).
Out of this world: Steaming vent of a fumarole - an alien landscape? (MF)