July 29, 2026 — Sulfur Cone gas monitoring maintenance, Mauna Loa

The continuously monitoring Multi-Gas instrument at Sulfur Cone is housed inside a black Pelican case, held down by rocks piled on top to keep secure from high winds. Air is pulled into the instrument via a small pump to be analyzed for volcanic gases (Sulfur Dioxide, Hydrogen Sulfide, Carbon Dioxide and Water Vapor). Meteorological parameters (Wind Speed/Wind Direction, Temperature/Humidity) along with fumarole temperature are also collected at the site. Monitoring the ratios of the different volcanic gases here can help USGS Hawaiian Volcano Observatory gas scientists identify any changes to the magmatic system beneath Mauna Loa. A gas scientist works in the background with the steaming 1950 eruptive fissure extending behind. USGS photo by C. Sealing.