Explosive dome eruptions modulated by periodic gas‐driven inflation

Johnson, J. B.; Lyons, J. J.; Andrews, B. J.; Lees, Jonathan M.

doi:10.1002/2014gl061310

Cited by 47 publications

(83 citation statements)

References 29 publications

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“…Such values are plausible, being in broad accordance with observations of the longevity of Vulcanian explosions (seconds) and bomb ejection velocities (∼100 ms −1 ) during similar transitional rhyolitic activity at Cordón Caulle in January 2012 (Schipper et al, 2013). These results also match estimated gas rise velocities of 50 ms −1 within fracture networks in the shallow conduit at the dacitic Santiaguito lava dome, Guatemala (Johnson et al, 2014) and an estimate of the gas velocity in a different tuffisite vein from Chaitén of at least meters per second (Berlo et al, 2013).…”

Section: Magnitudes and Rates Of Decompressionsupporting

confidence: 89%

Conduit Dynamics in Transitional Rhyolitic Activity Recorded by Tuffisite Vein Textures from the 2008–2009 Chaitén Eruption

et al. 2016

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The mechanisms of hazardous silicic eruptions are controlled by complex, poorly-understood conduit processes. Observations of recent Chilean rhyolite eruptions have revealed the importance of hybrid activity, involving simultaneous explosive and effusive emissions from a common vent. Such behavior hinges upon the ability of gas to decouple from magma in the shallow conduit. Tuffisite veins are increasingly suspected to be a key facilitator of outgassing, as they repeatedly provide a transient permeable escape route for volcanic gases. Intersection of foam domains by tuffisite veins appears critical to efficient outgassing. However, knowledge is currently lacking into textural heterogeneities within shallow conduits, their relationship with tuffisite vein propagation, and the implications for fragmentation and degassing processes. Similarly, the magmatic vesiculation response to upper conduit pressure perturbations, such as those related to the slip of dense magma plugs, remains largely undefined. Here we provide a detailed characterization of an exceptionally large tuffisite vein within a rhyolitic obsidian bomb ejected during transitional explosive-effusive activity at Chaitén, Chile in May 2008. Vein textures and chemistry provide a time-integrated record of the invasion of a dense upper conduit plug by deeper fragmented magma. Quantitative textural analysis reveals diverse vesiculation histories of various juvenile clast types. Using vesicle size distributions, bubble number densities, zones of diffusive water depletion, and glass H 2 O concentrations, we propose a multi-step degassing/fragmentation history, spanning deep degassing to explosive bomb ejection. Rapid decompression events of ∼3-4 MPa are associated with fragmentation of foam and dense magma at ∼200-360 m depth in the conduit, permitting vertical gas and pyroclast mobility over hundreds of meters. Permeable pathway occlusion in the dense conduit plug by pyroclast accumulation and sintering preceded ultimate bomb ejection, which then triggered a final bubble nucleation event. Our results highlight how the vesiculation response of magma to decompression events is highly sensitive to the local melt volatile concentration, which is strongly spatially Saubin et al.Chaitén Tuffisites Record Conduit Processes heterogeneous. Repeated opening of pervasive tuffisite vein networks promotes this heterogeneity, allowing juxtaposition of variably volatile-rich magma fragments that are derived from a wide range of depths in the conduit. This process enables efficient but explosive removal of gas from rhyolitic magma and creates a complex textural collage within dense rhyolitic lava, in which neighboring fused clasts may have experienced vastly different degassing histories.

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Section: Magnitudes and Rates Of Decompressionsupporting

confidence: 89%

Conduit Dynamics in Transitional Rhyolitic Activity Recorded by Tuffisite Vein Textures from the 2008–2009 Chaitén Eruption

et al. 2016

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“…But if the pressurization cycle is at a much shorter period (e.g. Santiaguito interval = 26 minutes, Johnson et al, 2014), then the InSAR deformation signal will be aliased and lost.…”

Section: Discussionmentioning

confidence: 99%

Persistent growth of a young andesite lava cone: Bagana volcano, Papua New Guinea

Wadge

McCormick

Edmonds

et al. 2018

Journal of Volcanology and Geothermal Research

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Bagana, an andesite lava cone on Bougainville Island, Papua New Guinea, is thought to be a very young central volcano. We have tested this idea by estimating the volumes of lava extruded over different time intervals (1-, 2-, 3-, 9-, 15-, 70-years) using digital elevation models (DEMs), mainly created from satellite data. Our results show that the long-term extrusion rate at Bagana, measured over years to decades, has remained at about 1.0 m 3 s -1 . We present models of the total edifice volume, and show that, if our measured extrusion rates are representative, the volcano could have been built in only ~300 years. It could also possibly have been built at a slower rate during a longer, earlier period of growth. Six kilometres NNW of Bagana, an andesite-dacite volcano, Billy Mitchell, had a large, caldera-forming plinian eruption 437 years ago. We consider the possibility that, as a result of this eruption, the magma supply was diverted from Billy Mitchell to Bagana. It seems that Bagana is a rare example of a very youthful, polygenetic, andesite volcano. The characteristics of such a volcano, based on the example of Bagana, are: a preponderance of lava products over pyroclastic products, a high rate of lava extrusion maintained for decades, a very high rate of SO 2 emission, evidence of magma batch fractionation and location in a trans-tensional setting at the end of an arc segment above a very steeply dipping and rapidly converging subduction zone 2

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“…However, these signals are mixed with many other processes associated with dome growth that may lead to deformation over a wide range of temporal and spatial scales. For example, internal pressurization of the lava dome may have large effects on the development of an eruption [ Sparks , ] but may also lead to deformation due to the repeated sealing of gas pathways on timescales of minutes [ Johnson et al , ] to days or weeks [ Ichihara et al , ; Matthews et al , ]. Experimental data show that on timescales of hours to years dome deformation may also be driven by densification due to the viscous reorganization of pores by surface tension [ Kennedy et al , ].…”

Section: Introductionmentioning

confidence: 99%

Volcano dome dynamics at Mount St. Helens: Deformation and intermittent subsidence monitored by seismicity and camera imagery pixel offsets

et al. 2016

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The surface deformation field measured at volcanic domes provides insights into the effects of magmatic processes, gravity‐ and gas‐driven processes, and the development and distribution of internal dome structures. Here we study short‐term dome deformation associated with earthquakes at Mount St. Helens, recorded by a permanent optical camera and seismic monitoring network. We use Digital Image Correlation (DIC) to compute the displacement field between successive images and compare the results to the occurrence and characteristics of seismic events during a 6 week period of dome growth in 2006. The results reveal that dome growth at Mount St. Helens was repeatedly interrupted by short‐term meter‐scale downward displacements at the dome surface, which were associated in time with low‐frequency, large‐magnitude seismic events followed by a tremor‐like signal. The tremor was only recorded by the seismic stations closest to the dome. We find a correlation between the magnitudes of the camera‐derived displacements and the spectral amplitudes of the associated tremor. We use the DIC results from two cameras and a high‐resolution topographic model to derive full 3‐D displacement maps, which reveals internal dome structures and the effect of the seismic activity on daily surface velocities. We postulate that the tremor is recording the gravity‐driven response of the upper dome due to mechanical collapse or depressurization and fault‐controlled slumping. Our results highlight the different scales and structural expressions during growth and disintegration of lava domes and the relationships between seismic and deformation signals.

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Explosive dome eruptions modulated by periodic gas‐driven inflation

Cited by 47 publications

References 29 publications

Conduit Dynamics in Transitional Rhyolitic Activity Recorded by Tuffisite Vein Textures from the 2008–2009 Chaitén Eruption

Conduit Dynamics in Transitional Rhyolitic Activity Recorded by Tuffisite Vein Textures from the 2008–2009 Chaitén Eruption

Persistent growth of a young andesite lava cone: Bagana volcano, Papua New Guinea

Volcano dome dynamics at Mount St. Helens: Deformation and intermittent subsidence monitored by seismicity and camera imagery pixel offsets

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