火山からの噴気による熱エネルギーとH₂0の放出量 : Plume riseからの推定

抄録

Heat discharge from fumaroles, which is the major part of the total energy released from volcanoes at non-eruptive stage, has been estimated mainly by direct measurements of issuing mass flux and temperature. However, the direct measurements are not applicable to inaccesible areas, such as crater floors or active fumarolic zones, especially at the time of increasing volcanic activity. Hence, it is highly desirable to establish a method which can evaluate the amount of heat discharge due to fumarolic activity safely and easily. The relation between heat energy release rate Q (W) and plume rise height h(m) was given by Briggs (1969) as Q=2.6x1O⁴ h³u³x^-2, where x is horizontal distance from the heat sorce in meter and u is the horizontal wind velocity in m/sec. The above Briggs' fomula was modified as h=C t^2/3 and Q=2.6x10⁴uC³, where t is the time in second. In the above formula, heat discharge rate Q can be estimated by determining the constant C and the wind velocity u with successive photographs of desired fumarolic plume. 0n the other hand, the evaluation of mass flow of volatile components from active vents is one of the important problems of the volcanology. The amount of H₂ 0 emission can be estimated from Q based on some assumptions.