HVO scientists measure volcanic gasses—Kīlauea caldera floor, July 22

HVO scientists walk transects along the down-dropped portion of Kīlauea caldera floor as part of a gas survey conducted on July 22. The multigas instruments carried on the scientists' backs measure the amount of carbon dioxide (CO₂), sulfur dioxide (SO₂), water vapor (H₂O), and hydrogen sulfide (H₂S) via an inlet hose oriented toward the ground surface. These measurements will provide a map showing areas of the caldera floor where specific volcanic gases are being emitted and their concentrations. The light-colored ground the scientists are walking on is evidence of such gases interacting with, and altering, the darker volcanic rocks in the area. USGS image by K. Mulliken.