Physics of thermohydraulic explosions

Büttner, Ralf; Zimanowski, Bernd

doi:10.1103/physreve.57.5726

Cited by 112 publications

(105 citation statements)

References 14 publications

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“…We consider the idealized maar-diatreme end-member to be the result of discrete phreatomagmatic explosions in the subsurface caused by molten fuel-coolant interaction (MFCI), which involves premixing of melt and water (or slurry) followed by thermohydraulic detonation (Büttner and Zimanowski, 1998). MFCI is favored by: (1) low melt viscosity (mafic rather than silicic magmas) because a large viscosity contrast between melt and water acts against premixing; (2) small magma batches, which more easily premix and are emplaced rapidly into the hypabyssal environment with minimal time for degassing and crystallization; (3) low overall magma fluxes which favor the intrusion of small batches of magma and do not overwhelm available water; and (4) low melt vesicularity (Zimanowski et al, 1995), because the presence of compressible bubbles acts against the important process of magma fracture during rapid melt-water heat transfer, which is key in the thermohydraulic detonation phase of MFCI.…”

Section: Perspectives On the Spectrum And Research Gapsmentioning

confidence: 99%

Maars to calderas: end-members on a spectrum of explosive volcanic depressions

et al. 2015

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We discuss maar-diatremes and calderas as end-members on a spectrum of negative volcanic landforms (depressions) produced by explosive eruptions (note-we focus on calderas formed during explosive eruptions, recognizing that some caldera types are not related to such activity). The former are dominated by ejection of material during numerous discrete phreatomagmatic explosions, brecciation, and subsidence of diatreme fill, while the latter are dominated by subsidence over a partly evacuated magma chamber during sustained, magmatic volatile-driven discharge. Many examples share characteristics of both, including landforms that are identified as maars but preserve deposits from non-phreatomagmatic explosive activity, and ambiguous structures that appear to be coalesced maars but that also produced sustained explosive eruptions with likely magma reservoir subsidence. A convergence of research directions on issues related to magma-water interaction and shallow reservoir mechanics is an important avenue toward developing a unified picture of the maar-diatreme-caldera spectrum.

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Section: Perspectives On the Spectrum And Research Gapsmentioning

confidence: 99%

Maars to calderas: end-members on a spectrum of explosive volcanic depressions

et al. 2015

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“…Phreatomagmatic explosions are discrete localized events that produce outward propagating shock waves that fragment intruding magma as well as surrounding rock and other debris (Zimanowski et al 1997;Büttner and Zimanowski 1998;Büttner et al 2005). When these explosions occur in a debris-filled vent, the relative depth of the explosion, most easily discussed as scaled depth, influences whether material is transported out of the vent or confined to the subsurface .…”

Section: Variations In Relative Explosion Position and Energymentioning

confidence: 99%

Evidence for the relative depths and energies of phreatomagmatic explosions recorded in tephra rings

Graettinger

Valentine

2017

Bull Volcanol

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Experimental work and field observations have inspired the revision of conceptual models of how maar-diatreme eruptions progress and the effects of variable energy, depth, and lateral position of explosions during an eruption sequence. This study reevaluates natural tephra ring deposits to test these new models against the depositional record. Two incised tephra rings in the Hopi Buttes Volcanic Field are revisited, and published tephra ring stratigraphic studies are compared to identify trends within tephra rings. Five major facies were recognized and interpreted as the result of different transportation and depositional processes and found to be common at these volcanoes. Tephra rings often contain evidence of repeated discrete phreatomagmatic explosions in the form of couplets of two facies: (1) massive lapilli tuffs and tuff breccias and (2) overlying thinly stratified to crossstratified tuffs and lapilli tuffs. The occurrence of repeating layers of either facies and the occurrence of couplets are used to interpret major trends in the relative depth of phreatomagmatic explosions that contribute to these eruptions. For deposits related to near-optimal scaled depth explosions, estimates of the mass of ejected material and initial ejection velocity can be used to approximate the explosion energy. The 19 stratigraphic sections compared indicate that near-optimal scaled depth explosions are common and that the explosion locations can migrate both upward and downward during an eruption, suggesting a complex interplay between water availability and magma flux. Reverse to normal coarse-tail graded tuff breccias inferred to be the product of closely timed phreatomagmatic explosions, and deposits of magmatic gas-driven explosions, were observed interspersed with discrete explosion deposits. This study not only provides a framework for more detailed interpretations of eruption sequences from tephra rings but also highlights the gap in our understanding of syn-eruptive hydrology and variations in magma flux that enables phreatomagmatic explosions.

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“…For instance, when magma encounters water, explosive interactions can result, with thermal energy from the magma transferred extremely rapidly to the external water, which flashes to steam and expands explosively (e.g., Wohletz 1986;Zimanowski et al 1991;Büttner and Zimanowski 1998). Jets resulting from this explosive expansion and entrainment comprise vertically travelling volcaniclastic debris (newly fragmented magma and pre-existing clasts), magmatic gases, and water vapour +/-liquid water that propagate upward toward the ground surface.…”

Section: Introductionmentioning

confidence: 99%

Rapid injection of particles and gas into non-fluidized granular material, and some volcanological implications

et al. 2008

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In diatremes and other volcanic vents, steep bodies of volcaniclastic material having differing properties (particle size distribution, proportion of lithic fragments, etc.) from those of the surrounding vent-filling volcaniclastic material are often found. It has been proposed that cylindrical or cone-shaped bodies result from the passage of "debris jets" generated after phreatomagmatic explosions or other discrete subterranean bursts. To learn more about such phenomena, we model experimentally the injection of gas-particulate dispersions through other particles. Analogue materials (glass beads or sand) and a finite amount of compressed air are used in the laboratory. The gas is made available by rapidly opening a valvetherefore the injection of gas and coloured particles into a granular host is a brief (<1 s), discrete event, comparable to what occurs in nature following subterranean explosions. The injection assumes a bubble shape while expanding and propagating upwards. In reaction, the upper part of the clastic host moves upward and outward above the 'bubble', forming a 'dome'. The doming effect is much more pronounced for shallow injection depths (thin hosts), with dome angles reaching more than 45°. Significant surface doming is also observed for some full-scale subterranean blasts (e.g. buried nuclear explosions), so it is not an artefact of our setup. What happens next in the experiments depends on the depth of injection and the nature of the host material. With shallow injection into a permeable host (glass beads), the compressed air in the "bubble' is able to diffuse rapidly through the roof. Meanwhile the coloured beads sediment into the transient cavity, which is also closing laterally because of inward-directed granular flow of the host. Depending on the initial gas pressure in the reservoir, the two-phase flow can "erupt" or not; non-erupting injections produce cylindrical bodies of coloured beads whereas erupting runs produce flaring upward or conical deposits. Changing the particle size of the host glass beads does not have a large effect under the size range investigated (100-200 to 300-400 µm). Doubling the host thickness (injection depth) requires a doubling of the initial gas pressure to produce similar phenomena. Such injections -whether erupting or wholly subterranean -provide a compelling explanation for the origin and characteristics of multiple cross-cutting bodies that have been documented for diatreme and other vent deposits.

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Physics of thermohydraulic explosions

Cited by 112 publications

References 14 publications

Maars to calderas: end-members on a spectrum of explosive volcanic depressions

Maars to calderas: end-members on a spectrum of explosive volcanic depressions

Evidence for the relative depths and energies of phreatomagmatic explosions recorded in tephra rings

Rapid injection of particles and gas into non-fluidized granular material, and some volcanological implications

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