RESUMO
Los métodos fundamentales para el estudio de gases para la vigilancia volcánica incluyen el muestreo en el campo con análisis de laboratorio, medidas de las tasas de emisión de los penachos volcánicos y vigilancia continua en el sitio. El muestreo de campo con análisis de laboratorio proporciona una información geoquímica detallado sobre un sitio en particular en un momento dado. Las medidas de emisión de gas revelan comunmente una relación promedia de SO2 y CO2, mientras que una vigilancia continua permite un entendimiento de los cambios temporales en las concentraciones de gases. Cada método tiene sus ventajas y desventajas y un estudio comprendido de gases para propósitos de vigilancia incluye la aplicación de tres acercamientos, conjuntamente con los métodos convencionales de vigilancia geofísica. (AU)
Assuntos
Erupções Vulcânicas , Geologia , Gases , Medição de RiscoRESUMO
Dead fir needles were collected from standing trees of Abies amabilis in five sites at the margin of the blast zone and located progressively farther from the eruption crater of Mount St. Helens. Scanning electron microscope techniques were used to determine patterns of cuticular melting for these needles and for Abies grandis needles which were heated at specific temperatures for 2 min. Comparisons between cuticular appearances of oven-heated needles and needles from Mount St. Helens were made to determine air temperatures at the collection sites at the time of the eruption. Air temperatures at these sites are estimated to have ranged from about 50 C to about 250 C. Analysis of cuticular sulfur content showed these needles adsorbed little or no volcanic S02 . Conifer needles provided a record of maximum air temperatures during the eruption, and helped reveal the pattern of heat distribution from the eruption cloud. This technique may prove useful for ecological studies in other heat-stressed habitats.
