Abstract : Volcanic activity at island arcs is typically characterized by a large variety of eruptive styles. The dynamism of the same volcano can as well be expressed by an alternance of "plinian" or "pelean" eruptions. The subject comprises two aspects related to the local activity of the Soufriere of Guadeloupe and the Mount Pelee : the study of the dynamics of a superficial magmatic chamber and the study of the phenomena related to the degassing of the products during magma ascent.
The first aspect consists in the study of a particular eruption of the Soufriere of Guadeloupe (1440 AD). The strategy of study was to couple a petrographic study of the products with an experimental study. This approach enabled us to well constrain the pre-eruptive conditions as well as the dynamics of the magmatic chamber which appears to be thermically and chemically zoned.
The second aspect consisted in the acquisition of natural and experimental data on the products of the historical eruptions of the Mount Pelee in order to bring new elements for the comprehension of the dynamism of the degassed andesitic magmas.
The nature of the products required to couple various approaches (textural study of the natural products, water content in residual glasses, anisotropy of magnetic susceptibility on domes, decompression experiments and experimental data acquisition at low pressure on a rhyolitic system).