Thermal vesiculation during volcanic eruptions

Lavallée, Yan; Dingwell, Donald B.; Johnson, J. B.; Cimarelli, C.; Hornby, Adrian; Kendrick, Jackie E.; Aulock, Felix W. von; Kennedy, Ben; Andrews, B. J.; Wadsworth, Fabian B.; Rhodes, Emma; Chigna, Gustavo

doi:10.1038/nature16153

Cited by 59 publications

(66 citation statements)

References 33 publications

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“…We assessed the relative volume fractions of gas and ash erupted during a single explosion and demonstrated that plumes from small‐to‐moderate size events at Santiaguito are extremely gas rich. The minor volume fraction of ash in the plume suggests that these events may not involve significant fragmentation of magma in the conduit and concurs with the recent suggestion that local sacrificial fragmentation along fault zones, due to shear‐induced thermal vesiculation, may be at the origin of such events [ Lavallée et al , ].…”

Section: Discussion and Conclusive Remarkssupporting

confidence: 84%

“…Explosions throughout the past decade have been of small to moderate size and have produced volatile‐rich plumes with relatively minor proportions of ash [ Yamamoto et al , ]. Recent petrological and geophysical analyses suggest that these small gas‐and‐ash explosions are not triggered by typical magmatic fragmentation but rather through sacrificial fragmentation that occurs along fault zones due to shear‐induced thermal vesiculation [ Lavallée et al , ].…”

Section: Activity At Santiaguitomentioning

confidence: 99%

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Characterization of moderate ash‐and‐gas explosions at Santiaguito volcano, Guatemala, from infrasound waveform inversion and thermal infrared measurements

Angelis

Lamb

Lamur

et al. 2016

Geophysical Research Letters

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The rapid discharge of gas and rock fragments during volcanic eruptions generates acoustic infrasound. Here we present results from the inversion of infrasound signals associated with small and moderate gas‐and‐ash explosions at Santiaguito volcano, Guatemala, to retrieve the time history of mass eruption rate at the vent. Acoustic waveform inversion is complemented by analyses of thermal infrared imagery to constrain the volume and rise dynamics of the eruption plume. Finally, we combine results from the two methods in order to assess the bulk density of the erupted mixture, constrain the timing of the transition from a momentum‐driven jet to a buoyant plume, and to evaluate the relative volume fractions of ash and gas during the initial thrust phase. Our results demonstrate that eruptive plumes associated with small‐to‐moderate size explosions at Santiaguito only carry minor fractions of ash, suggesting that these events may not involve extensive magma fragmentation in the conduit.

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Section: Discussion and Conclusive Remarkssupporting

confidence: 84%

Section: Activity At Santiaguitomentioning

confidence: 99%

Characterization of moderate ash‐and‐gas explosions at Santiaguito volcano, Guatemala, from infrasound waveform inversion and thermal infrared measurements

Angelis

Lamb

Lamur

et al. 2016

Geophysical Research Letters

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“…The processes triggering “vulcanian” gas‐and‐ash explosions at active lava domes remain widely debated as competing hypotheses exist at both all‐encompassing (Chouet et al, ) and volcano‐specific (Hall et al, ) scales. Vulcanian events have been attributed to a range of processes, from the ascent of a fresh batch of bubbly magma in the shallow conduit (Cassidy et al, ) and gas pressure accumulation due to fracture sealing (Kendrick et al, ; Okumura & Sasaki, ) healing (Gardner et al, ; Lamur et al, ) and cyclic gas fluxing (Michaut et al, ) to the development of shear fractures along the margins of volcanic conduits during ascent of highly viscous magma (Lavallée et al, ; Lensky et al, ; Tuffen et al, ). On the other hand, there is a general agreement on the processes that result in fracturing of parts of the dome during explosive activity to allow the ejection of ash‐laden plumes.…”

Section: Introductionmentioning

confidence: 99%

Brittle‐Ductile Deformation and Tensile Rupture of Dome Lava During Inflation at Santiaguito, Guatemala

et al. 2019

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Gas-and-ash explosions at the Santiaguito dome complex, Guatemala, commonly occur through arcuate fractures, following a 5-to 6-min period of inflation observed in long-period seismic signals. Observation of active faults across the dome suggests a strong shear component, but as fault propagation generally proceeds through the coalescence of tensile fractures, we surmise that explosive eruptions require tensile rupture. Here, we assess the effects of temperature and strain rate on fracture propagation and the tensile strength of Santiaguito dome lavas. Indirect tensile tests were conducted on samples with a porosity range of 3-30% and over diametral displacement rates of 0.04, 0.004, and 0.0004 mm/ s. At room temperature, the tensile strength of dome rock is rate independent (within the range tested) and inversely proportional to the porosity of the material. At eruptive temperatures we observe an increasingly ductile response at either higher temperature or lower displacement rate, where ductile deformation is manifest by a reduction in loading rate during constant deformation rate tests, resulting in slow tearing, viscous flow, and pervasive damage. We propose a method to conduct indirect tensile tests under volcanic conditions using a modification of the Brazilian disc testing protocol and use brittleness indices to classify deformation modes across the brittle-ductile transition. We show that a degree of ductile damage is inevitable in the lava core during explosions at the Santiaguito dome complex and discuss how strain leading to rupture controls fracture geometry, which would impact gas pressure release or buildup and regulate explosive activity.Plain Language Summary Using instruments we installed at Santiaguito, an active lava dome complex in Guatemala, we detected repeating cycles of inflation and deflation. The inflation took less time leading up to explosions compared to weak gas puffing, which led us to suspect that lava breaking and flowing might be responsible. To investigate this, we made laboratory tests where we put lava samples under tension, which is the most common way they break. We ran tests where we squeezed lavas at faster and slower rates in a press, and we also heated the lavas to their eruption temperatures-about 800°C-for some tests. Since the lavas contain volcanic glass, in some high temperature tests the glass partially flowed. In other tests the lavas were completely brittle, which means they stored up stress and then broke without flowing. The lava's behavior depends on the temperature and how fast they are squeezed. Finally, we considered how fast dome lavas at Santiaguito would have to be deformed to either break or stay intact during inflation of the dome. This study gives us a better idea of how dome lavas deform and how that affects hazardous activity during eruptions.

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“…In a conduit, this can relate to magma decompression driven by ascent, plug slip or edifice failure, as well as an increase in magma temperature (e.g., Sparks, 1978;Alibidirov and Dingwell, 1996;Lensky et al, 2008;Lavallée et al, 2015). The coincidence between dense borders of vesicular clasts and H 2 O depletion reflects an H 2 O concentrationdependent nucleation response to a decompression event ( Figure 5B; Castro et al, 2012).…”

Section: Vesicular Clast Textural Characteristics-vsdmentioning

confidence: 99%

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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Thermal vesiculation during volcanic eruptions

Cited by 59 publications

References 33 publications

Characterization of moderate ash‐and‐gas explosions at Santiaguito volcano, Guatemala, from infrasound waveform inversion and thermal infrared measurements

Characterization of moderate ash‐and‐gas explosions at Santiaguito volcano, Guatemala, from infrasound waveform inversion and thermal infrared measurements

Brittle‐Ductile Deformation and Tensile Rupture of Dome Lava During Inflation at Santiaguito, Guatemala

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

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