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Cross-section through the outer part of a 1930 Stromboli bomb. The area shown is a broken (not sawn) surface and measures 23 mm from top to bottom. Note the abundant bubbles <0.5 mm in diameter in the interior, which may represent impact vesiculation, and are a population that is absent from the chilled rind. Tick marks at top and bottom edges mark the lines of five bubble analysis traverses that are plotted in Figure 4.
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We highlight a potentially important trigger for bubble growth and degassing in volcanic bombs. We have successfully triggered bubble growth in previously unvesiculated samples of silicate melt during experiments to simulate volcanic bomb impact, by firing pellets at, and dropping weights onto, melt samples. We call this phenomenon "impact vesicula...
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... 4. Bubble sizes along five traverses perpendicular to the margin of the Figure 3 sample. Profiles were chosen so that some intersected the largest bubbles in the rind whereas others avoided them. Every discernable bubble encountered in each traverse is plotted, using a different symbol for each traverse. Measurements were made on a high-resolution version of Figure 3, with a lower bubble-size detection limit of 0.08 mm. The dip in maximum bubble size near 10 mm depth corresponds to the visually distinct boundary between rind and interior.
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... 4. Bubble sizes along five traverses perpendicular to the margin of the Figure 3 sample. Profiles were chosen so that some intersected the largest bubbles in the rind whereas others avoided them. Every discernable bubble encountered in each traverse is plotted, using a different symbol for each traverse. Measurements were made on a high-resolution version of Figure 3, with a lower bubble-size detection limit of 0.08 mm. The dip in maximum bubble size near 10 mm depth corresponds to the visually distinct boundary between rind and interior.
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It is generally assumed that spheroidal volcanic bombs are formed during cooling of molten clots pulled up into spheres by the surface tension of the magma. Also, volcanic bombs are regarded as non-fragmental structures, i.e. made of coherent material. We describe non-coherent, spheroidal bombs of mafic composition from the tuff/cinder cone of the...
Citations
... The degree of textural modifications is controlled by the temperature of the clasts and the rate of heat loss. Rapid deposition of juvenile pyroclasts at temperatures above the glass transition may permit: (1) microlite nucleation and growth (e.g., Szramek et al. 2010), (2) bubble nucleation, growth, collapse, and deformation (e.g., Rothery et al. 2007), (3) subsolidus transformation of minerals, e.g., Fe-Ti oxide and olivine (e.g., Haggerty and Baker 1967;Del Moro et al. 2013), and (4) ductile flattening, annealing and welding of pyroclasts (e.g., Giordano et al. 2005;Sumner et al. 2005;Bertagnini et al. 2011). Slow cooling of pyroclasts in situ is promoted by (i) larger clasts, as they cool more slowly, (ii) short transport times in the atmosphere, (iii) enhanced heat retention of the deposit due to high accumulation rates, and (iv) heat from the nearby vent, adjacent volcanic jets, or high temperature volatiles streaming through the vent and deposits (e.g., Sparks and Wright 1979;Sumner 1998;Sumner and Branney 2002;Woodcock et al. 2016). ...
Microlite crystallization in erupting basalt can occur in the conduit, in flight, or in situ after deposition. Distinguishing the products of primary versus secondary (post-fragmentation) crystallization can be challenging in near-vent environments, but is vital for interpreting shallow conduit conditions from pyroclast textures. Here, we examine pyroclasts of the 1886 basaltic Plinian eruption of Tarawera volcano, New Zealand, to assess the roles of primary versus secondary crystallization of microlites. Lapilli and ash were selected from (a) an ultra-proximal section (T47), < 100 m from vent, which is dominated by pyroclasts derived from the Plinian jet and column margin, and (b) a medial fall deposit section (T43), 2.5 km from the fissure, which contains products from the umbrella cloud. Strong contrasts in pyroclast groundmass crystallinities exist between sections, from near-holocrystalline (90–97% void-free corrected; VFC) in T47 pyroclasts to highly crystalline (77–83% VFC) in T43 pyroclasts. Subhedral-euhedral Fe–Ti microlites (< 3 μm) are ubiquitous and abundant in T47 pyroclasts, whereas they are virtually absent in T43 pyroclasts. Olivine is present in both T47 and T43 pyroclasts but evidence of its subsolidus transformation is only seen in T47 clasts, whereas in T43 clasts olivine is fresh. Near-complete crystallization of the groundmass and subsolidus transformation of olivine in the ultraproximal T47 clasts are evidence that post-depositional modification of primary pyroclast textures occurred in ultra-proximal environments at Tarawera as a response to high residual temperatures and oxidizing conditions, aided by short transport times of relatively coarse ejecta at high accumulation rates, likely supplemented by intense vent-derived heat. Ultra-proximal basaltic eruption products can continue to crystallize after deposition and are thus unlikely to be faithful indictors of shallow conduit magmatic processes; we recommend the use of medial and distal products instead.
... It is commonly assumed that seismic waves may induce bubble nucleation in magma, increasing magma overpressure, and potentially leading to unrest or an eruptive episode (e.g., Manga and Brodsky, 2006;Rothery et al., 2007;Cannata et al., 2010;Hamling and Kilgour, 2020;Seropian et al., 2021), yet this mechanism has never been validated experimentally. We did not observe any evidence suggesting that pressure oscillations triggered bubble nucleation in our experiments. ...
Magma ascending in the Earth’s crust can undergo oscillations in pressure, from ultra-low frequency changes associated with tectonics, to relatively higher frequency oscillations associated with seismicity. Seismic waves travelling through shallow magma bodies can lead to a range of unrest phenomena and potentially trigger volcanic eruptions. The mechanisms by which pressure oscillations can induce unrest or eruption remain debated. Here, we experimentally impose pressure oscillations on magma and study how they affect vesiculation processes. We use cylindrical samples (4.00 mm long, 4.85 mm diameter) of hydrous rhyolitic obsidian (0.11 ± 0.01 wt% H2O) placed in alumina (AL23) crucibles and vary pressure by the uniaxial loading of an alumina plunger in a thermo-mechanical analyzer. We monitor vesiculation at temperatures of 950–990°C and confining pressure of 177 kPa. We perform two types of experiment: 1) “static” experiments (at constant pressure) and 2) “oscillating” experiments in which we impose sinusoidal pressure oscillations of up to 71 kPa upon the static pressure (i.e., between 106 and 250 kPa). In both cases, we dilatometrically observe sample expansion driven by vesiculation. Post-experimental bubble textures reveal that bubbles formed preferentially at the sample margins. For the oscillating experiments, the sample expansion rate is lower than in the static experiments, and there are fewer vesicles at the sample margins. We examine the constituent processes of bubble formation (nucleation, growth, coalescence) and gas loss (diffusion, permeable flow) occurring during static experiments and with the added element of pressure oscillations. The most likely mechanism responsible for reduced sample expansion is that pressure oscillations drive the sample in and out of water saturation conditions and thus reduce the fraction of residence time over which bubble nucleation and/or growth are driven. Future work will be needed to confirm this hypothesis. These results are relevant to the study of earthquake-volcano interactions, where a magma body that sits close to volatile saturation is subject to pressure fluctuations.
... An applied stress during melt deformation may thus bring strain energy into the system and helps to distort and/or disrupt chains of silica tetrahedra that ultimately favor the formation of crystal nuclei. A decrease in activation energy during deformation-induced crystallization has been observed in various type of material such as polymers ( Sun et al., 1984;Chien and Weiss, 1988;Kumaraswamy et al., 1999;Xu et al., 2011), metal alloys ( Lee et al., 2006; Wang et al., 2015), oil and butter (Yang et al., 2011), and metals (e.g., Donovan and Stobbs, 1981;Chen et al., 1994) and might explain impact-induced vesiculation of magmas (Rothery et al., 2007;Carey et al., 2012). ...
Crystals and bubbles nucleate and grow in a magma that experiences a range of temperatures, pressures and strain-rates. We have a good conceptual and sometimes quantitative understanding of how crystallization and bubble nucleation are controlled by decompression and cooling. Here we explore the effect of strain-rate on the crystallization kinetics of magmas. In order to understand the interaction between deformation and crystallization, samples of basalt were deformed during their crystallization. We made measurements at subliquidus conditions (1160°C) and deformed samples in compression at strain-rates varying from 0 to 2 × 10–4 s–1 for a total strain of 0.31. We simultaneously imaged the samples using X-ray micro-tomography. Without deformation, no crystallization was observed over the course of a 260 min experiment. Once deformation was applied, crystallization initiated. Deformation increased the nucleation rate, increased crystal growth rates, and decreased the incubation time. Increasing the strain-rate, however, does not show a discernable effect of crystallization kinetics. We hypothesize that deformation may have an effect on the parameters that govern the crystallization kinetics of magmas, such as activation energy and diffusion by changing chemical potentials.
... As for a trigger mechanism, although Orr et al. (2013) confirm that high stand termination may be brought about by rockfalls impacting the lava surface, they also state that lava lake rise can be spurred by debris impacting the lake, albeit rarely. Experimental work by Sumner et al. (2007) demonstrates that vesiculation can be induced in samples of heated rhyolite simply by sudden impact with another object (e.g., airgun pellet, metal cylinder). They apply their results to volcanic bombs, asserting that some vesicles in bombs may be the result of the bomb's impact on the ground surface. ...
... It is well known that liquids supersaturated with dissolved gas like carbonated beverages nucleate numerous bubbles when agitated, and if the liquid is in a sealed container which is then opened, under-pressurized bubbles enlarge and rise rapidly, creating an overflowing foam (Rothery et al., 2007). Thick foam layers may also play a significant role during basaltic eruptions (Jaupart and Vergniolle, 1988). ...
Non-Newtonian rheology is typical for the high-level radioactive waste (HLW) slurries to be processed in the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Hydrogen and other flammable gases are generated in the aqueous phase by radiolytic and chemical reactions. HLW slurries have a capacity for retaining gas characterized by the shear strength holding the bubbles still. The sizes and degassing characteristics of flammable gas bubbles in the HLW slurries, expected to be processed by the WTP are important considerations for designing equipment and operating procedures. Slurries become susceptible to degassing as the bubble concentration increases over a maximum value that depends on shear strength. This susceptibility and the process of ebullitive bubble enlargement are described here. When disturbed, the fluid undergoes localized flow around neighboring bubbles which are dragged together and coalesce, producing an enlarged bubble. For the conditions considered in this work, bubble size increase is enough to displace the weight required to overcome the fluid shear strength and yield the surroundings. The buoyant bubble ascends and accumulates others within a zone of influence, enlarging by a few orders of magnitude. This process describes how the first bubbles appear on the surface of a 7 Pa shear strength fluid a few seconds after being jarred.
... They suggested that a depressurization of the volcanic plumbing system was responsible for the seismicity change. Earthquake volcano interactions have also been examined by Manga and Brodsky (2006); Sumner et al. (2007); Brodsky et al. (1998), these authors suggest that the passage of large seismic waves through a volcano may disrupt magma and bubbles in a pressurized system, leading to a process called rectified diffusion. Rectified diffusion is a mechanism by which a strain wave can rapidly pump volatiles into a bubble and therefore increase the pressure in a closed system. ...
In this thesis, we study the seismo-volcanic source localization using data recorded by new sensor arrays composed of three-component (3C) seismometers deployed on Ubinas stratovolcano (Peru). We develop a new framework (MUSIC-3C) of source localization method based on the well-known MUSIC algorithm. To investigate the performance of the MUSIC-3C method, we use synthetic datasets designed from eight broadband isotropic seismic sources located beneath the crater floor at different depths. The fundamental scheme of the MUSIC-3C method exploits the fact of the cross-spectral matrix of 3C array data, corresponding to the first seismic signal arrivals, provides of useful vector components (slowness, back-azimuth and incidence angle) from the seismic source. Application of the MUSIC-3C method on synthetic datasets shows the recovery of source positions. Real data used in this study was collected during seismic measurements with two seismic antennas deployed at Ubinas volcano in 2009, whose experiment conduced by volcanic teams of IRD-France (l'Institute de Recherche pour le Déveleppment), Geophysics group University College Dublin Ireland and Geophysical Institute of Peru (IGP). We apply the MUSIC-3C algorithm to investigate wave fields associated with the magmatic activity of Ubinas volcano. These analysis evidence a complex mechanism of vulcanian eruptions in which their seismic sources are found at two separated sources located at depths of 300 m and 1100 m beneath the crater floor. This implies the reproduction of similar mechanisms into the conduit. Based on the eruptive mechanisms proposed for other volcanoes of the same type, we interpret the position of this sources as the limits of the conduit portion that was involved in the fragmentation process.
The geophysical detection of magma bodies and the estimation of the dimensions, physical properties, and the volume fraction of each phase composing the magma is required to improve the forecasting of volcanic hazards and to understand transcrustal magmatism. We develop an analytical model to calculate P waves velocity in a three-phase magma consisting of crystals and gas bubbles suspended in a viscous melt. We apply our model to calculate the speed of sound as a function of the temperature in three magmas with different chemical compositions, representative of the diversity that is encountered in arc magmatism. The model employs the coupled phase theory that explicitly accounts for the exchanges of momentum and heat between the phases. We show that the speed of sound varies non-linearly with the frequency of an acoustic perturbation between two theoretical bounds. The dispersion of the sound in a magma results from the exchange of heat between the melt and the dispersed phases that affects the magnitude of their thermal expansions. The lower bound of the sound speed occurs at low frequencies for which all the constituents can be considered in thermal equilibrium, whereas the upper bound occurs at high frequencies for which the exchange of heat between the phases may be neglected. The presence of gas in a magma produces a sharp decrease in the velocity of compressional waves and generates conditions in which the dispersion of the sound is significant at the frequencies usually considered in geophysics. Finally, we compare the estimates of our model with the ones from published relationships. Differences are largest at higher frequencies and are <10% for typical magma.
Changbaishan Tianchi volcano is one of the most dangerous active volcanoes in Northeast Asia. It experienced three periods of large-scale eruptions since the Holocene, i.e. the Tianwenfeng period at about 5, 000 years ago, the Qixiangzhan period at about 4, 000 years ago and the Millennium eruption at about 1, 100 years ago, respectively. The type of Tianwenfeng and Millennium eruptions is commonly accepted to be a typical Plinian eruption. However, there arises a considerable debate about the type of Qixiangzhan eruption as whether it is effusive or explosive. In high-resolution remote-sensing images, the morphology of the products of Qixiangzhan eruption looks like a lava flow, which erupts from Qixiangzhan parasitic crater, and flows along the northern slope of the volcanic cone about 5.4 km in length and 400~800 m in width. However, the recent researches by the author have revealed that the Qixiangzhan eruption should be a small-scale pulsed explosive eruption. The main evidence is as follows: 1) The bulk-rock composition of Qixiangzhan eruption products is characterized by high SiO2 (≥71%) and Na2O+K2O (≥10%) contents representative of alkaline magma, which has high viscosity, low flowing ability and extremely high potential of explosive eruption; 2) Field observations show that the Qixinagzhan eruption products appear as thin layers about 2~5cm in thickness, the central part of which is welded stronger than the edge, significantly different from the massive or slaggy structures of lava flow. In addition, flame structures indicative of explosive eruption are well developed in the volcanic deposits around parasitic crater; 3) Microscopic observation reveals that most of the phenocrysts in the Qixiangzhan eruption products were severely broken by explosion to form angular grains with well developed micro-cracks. The vesicles in the Qixiangzhan eruption products are irregular in shape and have rough margin, different significantly from the elliptical and smooth margin vesicles commonly observed in lava flow; 4) Stereomicroscopic observation shows that the Qixiangzhan eruption products are composed of clastic particles and exhibit grain-supported texture with well developed irregular vesicles. Based on the above analyses, we may conclude that the Qixiangzhan eruption can be assigned to a small-scale pulsed explosive eruption. During the explosive eruption, a large number of fine pyroclastic particles flowed down the mountain slope as a high speed pyroclasstic flow to form thin layer of ignimbrite under the action of high temperature and strong shear forces. Over many times of explosive eruptions, layer upon layer of ignimbrite were accumulated, resulting in a shape just like lava flow. Therefore, all the three large eruptions of Changbaishan Tianchi volcano in Holocene can be assigned to explosive eruption, rather than the previously proposed model of explosive-effusive-explosive explosions.
Magmatic volatiles play a crucial role in volcanism, from magma production at depth to generation of seismic phenomena to control of eruption style. Accordingly, many models of volcano dynamics rely heavily on behavior of such volatiles. Yet measurements of emission rates of volcanic gases have historically been limited, which has restricted model verification to processes on the order of days or longer.
UV cameras are a recent advancement in the field of remote sensing of volcanic SO2 emissions. They offer enhanced temporal and spatial resolution over previous measurement techniques, but need development before they can be widely adopted and achieve the promise of integration with other geophysical datasets. Large datasets require a means by which to quickly and efficiently use imagery to calculate emission rates. We present a suite of programs designed to semi-automatically determine emission rates of SO2 from series of UV images. Extraction of high temporal resolution SO2 emission rates via this software facilitates comparison of gas data to geophysical data for the purposes of evaluating models of volcanic activity and has already proven useful at several volcanoes.
Integrated UV camera and seismic measurements recorded in January 2009 at Fuego volcano, Guatemala, provide new insight into the system’s shallow conduit processes. High temporal resolution SO2 data reveal patterns of SO2 emission rate relative to explosions and seismic tremor that indicate tremor and degassing share a common source process. Progressive decreases in emission rate appear to represent inhibition of gas loss from magma as a result of rheological stiffening in the upper conduit. Measurements of emission rate from two closely-spaced vents, made possible by the high spatial resolution of the camera, help constrain this model.
UV camera measurements at Kilauea volcano, Hawaii, in May of 2010 captured two occurrences of lava filling and draining within the summit vent. Accompanying high lava stands were diminished SO2 emission rates, decreased seismic and infrasonic tremor, minor deflation, and slowed lava lake surface velocity. Incorporation of UV camera data into the multi-parameter dataset gives credence to the likelihood of shallow gas accumulation as the cause of such events.
