Chemical composition of volcanic gases

By: Giggenbach, W.F. (Institute of Geological & Nuclear Sciences Limited, Nuclear Sciences. Lower Hutt).
Material type: materialTypeLabelBookSeries: Institute of Geological & Nuclear Sciences contribution ; 225.Subject(s): GASES | VOLCANOES | CHEMICAL ANALYSIS | GEOCHEMISTRY | MAGMAS | VISCOSITY | DEGASSING | ACIDIC MAGMAS | MAFIC MAGMAS | GEOLOGIC HAZARDS | CHEMICAL COMPOSITION | HALOGENS | TECTONICS | REDOX POTENTIAL | WATER | HYDROGEN | CARBON DIOXIDE | SULPHUR DIOXIDE | HYDROGEN SULPHIDE | CHEMICAL EQUILIBRIUM | ELECTROCHEMISTRY | METHANE | CARBON MONOXIDE | RN=1333-74-0 | RN=124-38-9 | RN=630-08-0 | RN=7783-06-4 | RN=7446-09-5
Incomplete contents:
Collection of volcanic gas samples suitable for detailed chemical analysis is generally restricted to volcanoes in comparatively mild, fumarolic states of activity. Of the volcanoes associated with the three major types of magmas, such conditions are most commonly encountered at andesitic volcanoes where comparatively high gas contents, intermediate magma viscosities and sufficiently low solidus temperatures combine to prolong the degassing process and allow channel ways for the gases escaping form deeper magma bodies to remain open. In the case of basaltic magmas, the low viscosities promote rapid separation of volatiles and melt, giving rise to extensive removal of volatiles during effusive eruptions, with the essentially degassed magma freezing at high temperature thus impeding steady-state degassing during non-eruptive periods, For rhyolitic magmas the situation is reversed, there high viscosities keep high amounts of volatiles dissolved in the magma to be released, in part only during violent eruptions. Because of their large numbers, their propensity for comparatively violent eruptions and frequently close association with populated areas, andesitic volcanoes represent probably the most important source of volcanic hazard. In combination with frequently also favorable conditions for volcanic gas sampling, techniques based on gas geochemistry, therefore, are especially valuable in the surveillance of this type of volcano. Before discussing the processes affecting the composition of volcanic gases, as discharged at the surface in detail, an attempt is made to evaluate first processes controlling the composition of magmatic gases, those dissolved in the original melt. (auth)
Tags from this library: No tags from this library for this title. Log in to add tags.
Item type Current location Call number Copy number Status Date due Barcode
ABSTRACT ABSTRACT NIWA BIBLIOGRAPHY
1 Available 100830-1001

Submitted for publication: Manual of volcano monitoring

Collection of volcanic gas samples suitable for detailed chemical analysis is generally restricted to volcanoes in comparatively mild, fumarolic states of activity. Of the volcanoes associated with the three major types of magmas, such conditions are most commonly encountered at andesitic volcanoes where comparatively high gas contents, intermediate magma viscosities and sufficiently low solidus temperatures combine to prolong the degassing process and allow channel ways for the gases escaping form deeper magma bodies to remain open. In the case of basaltic magmas, the low viscosities promote rapid separation of volatiles and melt, giving rise to extensive removal of volatiles during effusive eruptions, with the essentially degassed magma freezing at high temperature thus impeding steady-state degassing during non-eruptive periods, For rhyolitic magmas the situation is reversed, there high viscosities keep high amounts of volatiles dissolved in the magma to be released, in part only during violent eruptions. Because of their large numbers, their propensity for comparatively violent eruptions and frequently close association with populated areas, andesitic volcanoes represent probably the most important source of volcanic hazard. In combination with frequently also favorable conditions for volcanic gas sampling, techniques based on gas geochemistry, therefore, are especially valuable in the surveillance of this type of volcano. Before discussing the processes affecting the composition of volcanic gases, as discharged at the surface in detail, an attempt is made to evaluate first processes controlling the composition of magmatic gases, those dissolved in the original melt. (auth)

IGNS pre-publication January 1994

GN

NS

Security Code: 1

There are no comments on this title.

to post a comment.

Powered by Koha