A faint red light, caused by sulfur combustion, illuminated the crater of Poás Volcano last week. The phenomenon was captured early in the evening by the webcam of the Volcanological and Seismological Observatory (OVSICORI), according to volcanologist Geoffroy Avard.
According to the expert, incandescence occurs when sulfur reaches temperatures close to 250°C, at which point it combusts. “We observed incandescence, and direct observations show that it consists of a small, not very bright red light, corresponding to the combustion temperature of sulfur,” Avard explained.
Blueish Plume and Toxic Gases
This combustion generates a blueish plume, rich in sulfur dioxide (SO₂), one of the main toxic gases released by the volcano during its activity. “It’s a sulfur combustion light that generates these slightly bluer plumes, rich in sulfur dioxide,” added the volcanologist. The plume rises about 200 meters above the crater and disperses southwestward, driven by high-altitude winds.
Continuing Activity
Despite this visual manifestation, Ovsicori notes that Poás has maintained stable activity for several days, with less variability in the intensity of its eruptive pulses. “In general, it has been stable for a few days. It presents frequent pulses, which are small to moderate, and these are usually accompanied by ash emissions when visually observed,” explained Avard.
