Subsidence of ash-flow calderas: Relation to caldera size and magma-chamber geometry

摘要: Diverse subsidence geometries and collapse processes for ash-flow calderas are inferred to reflect varying sizes, roof geometries, depths of the source magma chambers, in combination with prior volcanic regional tectonic influences. Based largely on a review features at eroded pre-Quaternary calderas, continuum styles is exist, both island-arc continental settings, between small funnel larger plate (piston) subsidences bounded by arcuate faults. Within most ring-fault subsided block variably disrupted, due differential movement during eruptions postcollapse magmatism, but highly chaotic piecemeal appears be uncommon large-diameter calderas. Small-scale downsag structures accompanying extensional fractures develop along margins early stages subsidence, dominant only that have not deeply. Calderas loci multicyclic eruption cycles complex internal structures. Large flared inner topographic walls landsliding unstable slopes, resulting slide debris can constitute large proportions caldera fill. Because concentrated near walls, models from geophysical data suggest geometry, even plate-subsidence ring Simple geometric indicate many 3–5 km, greater than depth naturally exposed sections intracaldera deposits. Many intrusive complexes been recognized western U.S., Japan, elsewhere, no well-documented examples large-scale geometry or chaotically disrupted floors. Reported ignimbrite "shields" central Andes, where large-volume ash-flows erupted without collapse, seem alternatively interpretable as more conventional were filled overflow younger lavas tuffs. Some subcaldera intrusions provide insights concerning processes, such may continue evolve volume, depth, composition after formation associated