Experimental studies of collapse calderas

Martı́, Joan; Ablay, G. J.; Redshaw, L. T.; Sparks, R. S. J.

doi:10.1144/gsjgs.151.6.0919

Cited by 199 publications

(143 citation statements)

References 28 publications

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“…It is widely believed that the volume of caldera collapse is within the same order as the total volume of magma erupted (e.g. Marti et al, 1994). Here, we assumed that, in the case of maximum collapse, the chamber of 85 km 3 collapsed completely and the topmost part, 15 × 10 km wide, the same as the present caldera width, fell to a depth of 700 m [= 85 km 3 / (15 km/2 × 10 km/2 × π)].…”

Section: Geometry Of the Caldera Pre-and Post-collapsementioning

confidence: 99%

Numerical simulation of tsunamis generated by caldera collapse during the 7.3 ka Kikai eruption, Kyushu, Japan

2006

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The relationship between tsunamis and scales of caldera collapse during a 7.3 ka eruption of the Kikai volcano were numerically investigated, and a hypothetical caldera collapse scale was established. Wave height, arrival time, and run-up height and distance were determined at some locations along the coastline around Kikai caldera, using non-linear long-wave equations and caldera collapse models using parameters showing the difference in geometry between pre-and post-collapse and the collapse duration. Whether tsunamis become large and inundations occur in coasts is estimated by the dimensionless collapse speed. Computed tsunamis were then compared with geological characteristics found in coasts. The lack of evidence of tsunami inundation at Nejime, 65 km from the caldera, suggests that any tsunamis were small; indicating that the upper limit of dimensionless caldera collapse speed was 0.01. On the other hand, on the coast of the Satsuma Peninsula, 50 km from the caldera, geological characteristics suggests that tsunamis did not inundate, or that even if tsunamis inundated the area, the traces of a tsunami have been eroded by a climactic pyroclastic flow or the tsunami itself and they have not been left. In numerical computations, when a dimensionless caldera collapse speed is more than 0.003, tsunami can inundate this area.

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Section: Geometry Of the Caldera Pre-and Post-collapsementioning

confidence: 99%

Numerical simulation of tsunamis generated by caldera collapse during the 7.3 ka Kikai eruption, Kyushu, Japan

2006

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“…The way in which caldera collapse was accomplished was adapted from previous works (cf. Marti et al 1994;Walter and Troll 2001). The inflated rubber reservoir was placed at specific depth of the sand-pile and then partially deflated to locate the position of the caldera faults.…”

Section: Physical Modelingmentioning

confidence: 99%

“…The process of caldera subsidence has been modeled experimentally by a range of workers (e.g. Komuro 1987;Marti et al 1994;Branney 1995;Roche et al 2000;Walter and Troll 2001;Acocella et al 2001;Troll et al 2002;Kennedy et al 2004) who showed that caldera subsidence occurs mainly along outward-dipping ring faults that allow subsidence of the central caldera floor either as a piston, trapdoor, funnel or in piecemeal fashion. In these experiments, for simplicity, the ground surface above magma chambers was considered as either flat, i.e., no relief, or as a single cone placed directly above the magma chamber.…”

Section: Introductionmentioning

confidence: 99%

Large-scale failures on domes and stratocones situated on caldera ring faults: sand-box modeling of natural examples from Kamchatka, Russia

2004

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Edifices of stratocones and domes are often situated eccentrically above shallow silicic magma reservoirs. Evacuation of such reservoirs forms collapse calderas commonly surrounded by remnants of one or several volcanic cones that appear variously affected and destabilized. We studied morphologies of six calderas in Kamchatka, Russia, with diameters of 4 to 12 km. Edifices affected by caldera subsidence have residual heights of 250-800 m, and typical amphitheater-like depressions opening toward the calderas. The amphitheaters closely resemble horseshoe-shaped craters formed by large-scale flank failures of volcanoes with development of debris avalanches. Where caldera boundaries intersect such cones, the caldera margins have notable outward embayments. We therefore hypothesize that in the process of caldera formation, these eccentrically situated edifices were partly displaced and destabilized, causing largescale landslides. The landslide masses are then transformed into debris avalanches and emplaced inside the developing caldera basins. To test this hypothesis, we carried out sand-box analogue experiments, in which caldera formation (modeled by evacuation of a rubber balloon) was simulated. The deformation of volcanic cones was studied by placing sand-cones in the vicinity of the expected "caldera" rim. At the initial stage of the modeled subsidence, the propagating ring fault of the caldera bifurcates within the affected cone into two faults, the outermost of which is notably curved outward off the caldera center. The two faults dissect the cone into three parts: (1) a stable outer part, (2) a highly unstable and subsiding intracaldera part, and (3) a subsiding graben structure between parts (1) and (2). Further progression of the caldera subsidence is likely to cause failure of parts (2) and (3) with failed material sliding into the caldera basin and with formation of an amphitheater-like depression oriented toward the developing caldera. The mass of material which is liable to slide into the caldera basin, and the shape of the resulted amphitheater are a function of the relative position of the caldera ring fault and the base of the cone. A cone situated mostly outside the ring fault is affected to a minor degree by caldera subsidence and collapses with formation of a narrow amphitheater deeply incised into the cone, having a small opening angle. Accordingly, the caldera exhibits a prominent outward embayment. By contrast, collapse of a cone initially situated mostly inside the caldera results in a broad amphitheater with a large opening angle, i.e. the embayment of the caldera rim is negligible. The relationships between the relative position of an edifice above the caldera fault and the opening angle of the formed amphitheater are similar for the modeled and the natural cases of caldera/cone interactions. Thus, our experiments support the hypothesis that volcanic edifices affected by caldera subsidence can experience large-scale failures with formation of indicative amphitheaters oriented toward ...

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“…The formation of such calderas, which may be referred to as reverse-fault calderas to distinguish them from normal-fault calderas, has been discussed by many authors, both as regards theory (Anderson, 1936) and experiments (Komuro, 1987;Marti et al, 1994).…”

Section: Introductionmentioning

confidence: 99%

Stress fields generating ring faults in volcanoes

Guðmundsson¹,

Martı́²,

Turon³

1997

Geophysical Research Letters

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Abstract. Ring faults in volcanoes have been recognized for a long time, but their mechanics of formation is still poorly understood. While the subsidence on a ring fault during a large eruption from the associated chamber is easily understood, the initiation of the fault itself has been difficult to explain. For a ring fault to form, the tensile and shear stresses at the surface of the volcano must peak at a certain radial distance from the surface point above the center of the chamber. Empirical evidence, however, shows that during most periods of unrest in active volcanoes the stress field is not favorable for the initiation of ring faults. We made several tens of boundary-element models of magma chambers of various geometries and subject to different loading conditions. The results indicate that overpressure or underpressure in the chamber as the only loading is unlikely to initiate ring faults. For a spherical chamber subject to horizontal extension or doming, and a silllike chamber subject to horizontal extension, the tensile and shear stresses at the surface of the volcano peak at a certain radial distance from the surface point above the center of the chamber. Then, however, the maximum stresses occur at the boundary of the chamber itself, which would normally lead to sheet injection rather than to ring-fault formation. By contrast, a sill-like magma chamber subject to doming gives rise to a stress field suitable for the initiation of a ring fault.

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Experimental studies of collapse calderas

Cited by 199 publications

References 28 publications

Numerical simulation of tsunamis generated by caldera collapse during the 7.3 ka Kikai eruption, Kyushu, Japan

Numerical simulation of tsunamis generated by caldera collapse during the 7.3 ka Kikai eruption, Kyushu, Japan

Large-scale failures on domes and stratocones situated on caldera ring faults: sand-box modeling of natural examples from Kamchatka, Russia

Stress fields generating ring faults in volcanoes

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