What makes hydromagmatic eruptions violent? Some insights from the Keanakāko'i Ash, Kı̄lauea Volcano, Hawai'i

Mastin, Larry G.; Christiansen, Robert L.; Thornber, Carl R.; Lowenstern, Jacob B.; Beeson, Melvin H.

doi:10.1016/j.jvolgeores.2004.05.015

Cited by 83 publications

(79 citation statements)

References 33 publications

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“…The latter effect is due to extended vesicle growth and coalescence in the fountain in reticulite (Mangan and Cashman 1996). Our data are within the lower range for the fast-rising magma that produced a subplinian phase of the Keanakako'i deposit of Kilauea volcano (∼10 2 to 10 4 mm −3 ; Mastin et al 2004), and slightly larger than the range observed in scoria from sustained Hawaiian fire fountains (10 to 10 2 mm −3 ; Mangan and Cashman 1996;Mastin et al 2004). Thus we suggest that the early ascent rate of Stromboli's magma was between that of magma feeding the Keanakako'i eruption and magma that feeds Hawaiian-style explosions (Lautze and Houghton 2005).…”

Section: Distinction Between Hd Tt and Ld Texturessupporting

confidence: 57%

Linking variable explosion style and magma textures during 2002 at Stromboli volcano, Italy

2006

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Microtextural characteristics of fresh ejecta from Stromboli volcano were examined from three periods of differing eruption style and intensity in 2002. Activity shifted from relatively weak and infrequent ash-charged explosions during January through May into two broad cycles of waxing activity in June through late September, and late September through December, followed by the onset on 28 December of the 2002/2003 effusive eruption. Analyzed sets of lapilli from May, September/October, and 28 December show contrasts in the physical properties of magma resident in the shallow conduit during this range of activity. Three distinct textures are observed among the analyzed pyroclasts: low density (LD) with an abundance of subspherical bubbles, the presence of large, irregularly shaped bubbles, and a light-to-transparent glass matrix; transitional texture (TT) with an intermediate number of subspherical bubbles, a high frequency of large, irregularlyshaped bubbles, and a honey colored glass matrix; and high density (HD) with sparse relatively small bubbles, conspicuous large irregular bubbles, and a dark glass matrix. Observational and quantitative data (density, vesicle size) indicate that these textures are linked through variable residence time in Stromboli's shallow conduit, with an ongoing evolution from LD to HD magma. Calculations suggest that residual LD magma will evolve to HD texture in a period of hours to days. Contrasting amounts of the LD, TT, and HD magmas are present in each sample, with the most TT in May, the most LD in September/October, and the most HD in December. This implies that the shallow magma had a different rheology at each collection period. The viscosity of LD and HD magmas are calculated to be in the range of 2,000 to 2,600 and 3,000 to 5,000 Pa s, respectively, which, with their changing proportions, must have implications for rates of bubble slug ascent and processes of fragmentation. This study suggests that an increasing maturity of magma in Stromboli's shallow conduit (with resultant increase in viscosity) feeds back to reduce the intensity of explosions, whereas a steady flux of LD magma favors more powerful explosions.

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Section: Distinction Between Hd Tt and Ld Texturessupporting

confidence: 57%

Linking variable explosion style and magma textures during 2002 at Stromboli volcano, Italy

2006

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“…There is a significant body of literature suggesting that phreatomagmatic pyroclastic deposits can lend insight into eruptive energy, the amount of liquid water in the eruption column and flows, and the relative influence of external water at the vent (e.g., Fisher and Waters 1970;Crowe and Fisher 1973;Lorenz 1974;Sheridan and Wohletz 1983;Fisher and Schmincke 1984;Houghton and Hackett 1984;Kokelaar 1983Kokelaar , 1986Sohn and Chough 1989;Dellino et al 1990;Houghton et al 1999;White 1996White , 2001Nemeth et al 2001;Cole et al 2001;Mastin et al 2004;Brand and White 2007). It has been variously suggested that many characteristics of phreatomagmatic pyroclastic deposits, such as the presence or absence of features associated with liquid water (i.e., accretionary lapilli and bomb sags), bedding characteristics, and edifice morphology; can be attributed to the original amount of external water-tomelt mass ratio (Heiken 1971;Wohletz and McQueen 1984;Sheridan and Wohletz 1983).…”

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confidence: 99%

“…It has been variously suggested that many characteristics of phreatomagmatic pyroclastic deposits, such as the presence or absence of features associated with liquid water (i.e., accretionary lapilli and bomb sags), bedding characteristics, and edifice morphology; can be attributed to the original amount of external water-tomelt mass ratio (Heiken 1971;Wohletz and McQueen 1984;Sheridan and Wohletz 1983). This ratio may change many times throughout an eruption as a result of increasing or decreasing magma mass flux (Kokelaar 1983(Kokelaar , 1986, an increase or decrease in the source and abundance of external water (Brand and White 2007), fluctuations in mixing efficiency and turbulence (Büttner and Zimanowski 1998;Mastin et al 2004), variable influence of magmatic volatiles in fragmentation (Houghton et al 1999;Houghton and Hackett 1984;Houghton and Schmincke 1986;Houghton and Wilson 1989), and the relative effectiveness of vent sealing against external water (Cole et al 2001;Brand and White 2007).…”

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confidence: 99%

Eruptive conditions and depositional processes of Narbona Pass Maar volcano, Navajo volcanic field, Navajo Nation, New Mexico (USA)

2008

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Phreatomagmatic deposits at Narbona Pass, a mid-Tertiary maar in the Navajo volcanic field (NVF), New Mexico (USA), were characterized in order to reconstruct the evolution and dynamic conditions of the eruption. Our findings shed light on the temporal evolution of the eruption, dominant depositional mechanisms, influence of liquid water on deposit characteristics, geometry and evolution of the vent, efficiency of fragmentation, and the relative importance of magmatic and external volatiles. The basal deposits form a thick (5-20 m), massive lapilli tuff to tuff-breccia deposit. This is overlain by alternating bedded sequences of symmetrical to antidune cross-stratified tuff and lapilli tuff; and diffusely-stratified, clast-supported, reversely-graded lapilli tuffs that pinch and swell laterally. This sequence is interpreted to reflect an initial vent-clearing phase that produced concentrated pyroclastic density currents, followed by a pulsating eruption that produced multiple density currents with varying particle concentrations and flow conditions to yield the well-stratified deposits. Only minor localized soft-sediment deformation was observed, no accretionary lapilli were found, and grain accretion occurs on the lee side of dunes. This suggests that little to no liquid water existed in the density currents during deposition. Juvenile material is dominantly present as blocky fine ash and finely vesiculated fine to coarse lapilli pumice. This indicates that phreatomagmatic fragmentation was predominant, but also that the magma was volatile-rich and vesiculating at the time of eruption. This is the first study to document a significant magmatic volatile component in an NVF maar-diatreme eruption. The top of the phreatomagmatic sequence abruptly contacts the overlying minette lava flows, indicating no gradual drying-out period between the explosive and effusive phases. The lithology of the accidental clasts is consistent throughout the vertical pyroclastic stratigraphy, suggesting that the diatreme eruption did not penetrate below the base of the uppermost country rock unit, a sandstone aquifer ∼360 m thick. By comparison, other NVF diatremes several tens of kilometers away were excavated to depths of ∼1,000 m beneath the paleosurface (e.g.

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“…Hydromagmatic activity may involve quenching tens to hundreds of meters below the surface (Mastin et al 2004;Tuffen et al 2010). However, this would trigger phreatomagmatic fragmentation, creating fragmental deposits rather than the intact lava lobes that form the bulk of the samples analysed in this study.…”

Section: No Post-quenching Movementmentioning

confidence: 99%

Using dissolved H2O in rhyolitic glasses to estimate palaeo-ice thickness during a subglacial eruption at Bláhnúkur (Torfajökull, Iceland)

2012

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The last decade has seen the refinement of a technique for reconstructing palaeo-ice thicknesses based on using the retained H 2 O and CO 2 content in glassy eruptive deposits to infer quenching pressures and therefore ice thicknesses. The method is here applied to Bláhnúkur, a subglacially erupted rhyolitic edifice in Iceland. A decrease in water content from ∼0.7 wt.% at the base to ∼0.3 wt.% at the top of the edifice suggests that the ice was 400 m thick at the time of the eruption. As Bláhnúkur rises 350 m above the surrounding terrain, this implies that the eruption occurred entirely within ice, which corroborates evidence obtained from earlier lithofacies studies. This paper presents the largest data set (40 samples) so far obtained for the retained volatile contents of deposits from a subglacial eruption. An important consequence is that it enables subtle but significant variations in water content to become evident. In particular, there are anomalous samples which are either water-rich (up to 1 wt.%) or water-poor (∼0.2 wt.%), with the former being interpreted as forming intrusively within hyaloclastite and the latter representing batches of magma that were volatile-poor prior to eruption. The large data set also provides further insights into the strengths and weaknesses of using volatiles to infer palaeo-ice thicknesses and highlights many of the uncertainties involved. By using examples from Bláhnúkur, the quantitative use of this technique is evaluated. However, the relative pressure conditions which have shed light on Bláhnúkur's eruption mechanisms and syn-eruptive glacier response show that, despite uncertainties in absolute values, the volatile approach can provide useful insight into the mechanisms of subglacial rhyolitic eruptions, which have never been observed.

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What makes hydromagmatic eruptions violent? Some insights from the Keanakāko'i Ash, Kı̄lauea Volcano, Hawai'i

Cited by 83 publications

References 33 publications

Linking variable explosion style and magma textures during 2002 at Stromboli volcano, Italy

Linking variable explosion style and magma textures during 2002 at Stromboli volcano, Italy

Eruptive conditions and depositional processes of Narbona Pass Maar volcano, Navajo volcanic field, Navajo Nation, New Mexico (USA)

Using dissolved H2O in rhyolitic glasses to estimate palaeo-ice thickness during a subglacial eruption at Bláhnúkur (Torfajökull, Iceland)

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