This book consists of four parts. The first part (part. I) deals with magmas, the conditions of their genesis, and their ascent and evolution within the crust. We firstly present the main types of primary magmas, including the relevant petrological and geochemical characteristics of each type : mid-oceanic ridge basalts, intraplate basalts, mantle-derived andesites (boninites), and rhyolitic magmas resulting from crustal melting (examplified by the Macusani ignimbrites from Peru). Then we consider the different processes of magma transport in the crust, at both microscopic and macroscopic scales, and we look at some. of the physical properties that are relevant to their rheological behaviour (viscosity, tensile strength). Thereafter we present some aspects of the magma storage and evolution in the crust. This includes the major petrological processes of magmatic differentiation (crystal fractionation, magma mixing, contamination) as well as some insights into the geometry and structure of magmatic transport and storage systems under volcanoes. We address aJso the use of short-lived radioactive disequilibria in the study of magma storage and dynamics.
lo part II, we consider volcanic gases and primary volcanic products (lava flows and domes, pyroclastic deposits). We also address the varied eruptive mechanisms that produce the observed variety of volcanic products. Volcanic gases have variable composition and emission rate from which we learn about magmatic processes in general, and about the current activity of a give~volcano. Lavas have variable geometry, morphology, internal structure, mobility and flow behaviour, which depend on physical and chemical properties of magmas, on environmental factors e.g. subaerial or subaqueous emplacement) and on effusion rate. Pyroclastic products are erupted as pyroclast-gas mixtures fragmented then accelerated by decompression, either at depth or at the Earth's surface. Explosive eruptions need e:xsolution of magmatic gases (magmatic eruptions) and/or interaction of magma "th ground or external water (hydrovolcanic eruptions). Phreatic eruptions are a particular kind of eruption in which steam is explosively decompressed but no agma is erupted. Upon eruption, pyroclastic products may be emplaced as :roclastic fall, flow or surge deposits, lo part III, we firstly document the main types of volcanoes and volcanic systems. This includes monogenetic volcanoes (scoria cones, maars, tuff-rings and tuff-cones) exemplified by the Chaine des Puys field, stratovolcanoes with emphasis on the ide-world andesitic ones, basaltic shield volcanoes, flood basalt plateaux, bmarine seamounts and ridges, and large calderas. Volcanoes and volcanic terns are described in their form, internal structure and their temporal evolution in response to the magmatic and structural evolution of the system. We then address. some of the major tools currently used in studying modern and ancient volcanic terns : mapping and remote sensing in volcanic areas, datation of volcanic rocks
• geochronological methods, geophysical investigation of the internal structure and umbing system of volcanoes by seismic, gravity, magnetic and electric methods.
Part IV finally addresses volcanic hazards and the geophysical and geochemical moniroring of active volcanoes. General concepts and methods guiding the hazards assessment and zonation are firstly presented, then applications are given to the french active volcanoes of the Lesser Antilles arc (Montagne Pelee, Soufriere of

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