Volatile emissions from the crater and flank of Oldoinyo Lengai volcano, Tanzania

As a comparison to airborne infrared (IR) flux measurements, ground-based sampling of fumarole and soil gases was used to characterize the quiescent degassing of CO₂ from Oldoinyo Lengai volcano. Aerial and ground-based measurements are in good agreement: ∼75% of the aerially measured CO₂ flux at Lengai (0.05–0.06 × 10¹² mol yr⁻¹ or 6000–7200 tonnes CO₂ d⁻¹) can be attributed to seven large crater vents. In contrast to Etna and Vulcano Island, where 15–50% of the total CO₂ flux emanates diffusely through the volcanic flanks, diffuse emissions were measured only within 500 m of the crater rim at Lengai, contributing