Résumés
Summary
This paper combines the temporal model of caldera formation presented by Robert Smith and Roy Bailey in 1968 with recent volcanological concepts. Field examples, experimental models and theoretical studies are synthesized toillustrate the process of caldera collapse conceptually as a series of stages of eruption and deformation. During each stage, physical changes occur at the surface, within the underlying magma chamber, and within the subsiding block or blocks that lie between the surface and the top of the magma chamber. The stages are as follows: 1) magma chamber intrusion, 2) initial eruption, down sagging and the on set of subsidence, 3) main subsidence and eruption phase, 4) peripheral extension and eruption quiescence, 5) continued eruption, subsidence and change oferuptive style, and 6) resurgence and extrusion of lava domes and flows. These stages may then be repeated as a subsequent caldera cycle. Every caldera has an individual history and may deform in a different manner at each stage. The paper outlines how these stages can give rise to different caldera types.
Sommaire
Le présent article fait état des conceptset des publications les plus importantesen matière d'effondrement des caldeiras.On y présente également une vued'ensemble des différents types decaldeira, leurs caractéristiques illustréesd'exemples concrets, ainsi qu'unglossaire de la nomenclature afférente.Nous traiterons des concepts de piston,d'affaissement, d'effondrementconcentrique par paliers, ainsi que decaldeiras de style chaotique, de fossétectonique et fragmentaire. Il semblentque certaines caldeiras soient le résultatd'une combinaison de style. Nousconsidérons les interactions complexesde variables qui déterminent la structureet la morphologie des caldeiras et enconditionnent le style.
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