Fumarole Measurements Over Hydrothermal Systems

Abstract

Methods and theory of fumarole measurements are reviewed and the settings of representative surveys are discussed with reference to some data from the Karapiti fumarole field (NZ) collected during the past 50 years. In almost all cases there is disturbance by some inflow of air which becomes entrained in the turbulent steam jet. Reproducible measurements of the heat output of fumarole jets can be obtained where a jet is funnelled through a vertical pipe or where data are collected across the face of an exposed vent. Systematic errors occur where measurements are made at the ground level of 'crater fumaroles' above a steam vent. The output of inaccessible fumaroles can be estimated from plots of the heat output of accessible fumaroles versus normalised steam cloud area visible in air photos. The last method is suitable for monitoring long term changes in the heat output of fumarole fields occurring over many hydrothermal systems.