Petrological analysis of the pre-eruptive magmatic process prior to the 2006 explosive eruptions at Tungurahua volcano (Ecuador)

Samaniego, Pablo; Pennec, Jean–Luc Le; Robin, Claude; Hidalgo, Silvana

doi:10.1016/j.jvolgeores.2010.10.010

Cited by 108 publications

(115 citation statements)

References 54 publications

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“…Since then, the activity has fluctuated with phases of uneven intensity, size (VEI 1 to VEI 3) and style (strombolian, vulcanian, subplinian), while eruptive products have shown monotonous andesitic compositions (58-59 wt.% SiO 2 ; Samaniego et al 2011). Intense eruptive phases have occurred, e.g.…”

Section: Geological Setting and Recent Volcanic Activitymentioning

confidence: 99%

“…During the next hours, the activity continued to increase and reached its climax at about 0515 hours UTC on August 17 and lasted approximately 50-60 min: powerful and persistent incandescent jets rose up to 1 km above the crater, numerous pyroclastic flows rushed down to the rivers surrounding the volcano (Kelfoun et al 2009) (Fig. 1c), a sustained SO 2 -rich eruption column reached a height >15 km above the summit and the plume spread over the Inter-Andean Valley, west of the volcano, and the Pacific Ocean (Arellano et al 2008;Kelfoun et al 2009;Steffke et al 2010;Samaniego et al 2011) (Fig. 1a, b).…”

Section: Geological Setting and Recent Volcanic Activitymentioning

confidence: 99%

“…On August 17, andesitic lava flowed down the western flank, and tephra fall was restricted to the proximal area west of the volcano. Petrological investigations (Samaniego et al 2011) show that the August 2006 eruption was triggered by a massive injection of a gas-rich andesitic magma into the deep plumbing system, followed by a rapid ascent to the surface, thus enhancing explosivity. In this paper, we focus on the 2006 pyroclastic deposits of the August 16 event, with emphasis on the fall layers deposited on the Quero Plateau, an area located 7 to 20 km from the volcano (Fig.…”

Section: Geological Setting and Recent Volcanic Activitymentioning

confidence: 99%

“…3). The composition (58-59 wt.% SiO 2 ; Samaniego et al 2011) and the texture of the juvenile elements, along with geometric and facies characteristics, indicate that these deposits are typical block-and-ash scoria flow deposits (Freundt et al 2000).…”

Section: Pyroclastic Flow Depositsmentioning

confidence: 99%

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Causes and consequences of bimodal grain-size distribution of tephra fall deposited during the August 2006 Tungurahua eruption (Ecuador)

et al. 2011

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International audienceThe violent August 16–17, 2006 Tungurahua eruption in Ecuador witnessed the emplacement of numerous scoria flows and the deposition of a widespread tephra layer west of the volcano. We assess the size of the eruption by determining a bulk tephra volume in the range 42–57 × 106 m3, which supports a Volcanic Explosivity Index 3 event, consistent with calculated column height of 16–18 km above the vent and making it the strongest eruptive phase since the volcano’s magmatic reactivation in 1999. Isopachs west of the volcano are sub-bilobate in shape, while sieve and laser diffraction grain-size analyses of tephra samples reveal strongly bimodal distributions. Based on a new grain-size deconvolution algorithm and extended sampling area, we propose here a mechanism to account for the bimodal grain-size distribution. The deconvolution procedure allows us to identify two particle subpopulations in the deposit with distinct characteristics that indicate dissimilar transport-depositional processes. The log-normal coarse-grained subpopulation is typical of particles transported downwind by the main volcanic plume. The positively skewed, fine-grained subpopulation in the tephra fall layer shares close similarities with the elutriated co-pyroclastic flow ash cloud layers preserved on top of the scoria flow deposits. The area with the higher fine particle content in the tephra layer coincides with the downwind prolongation of the pyroclastic flow deposits. These results indicate that the bimodal distribution of grain size in the Tungurahua fall deposit results from synchronous deposition of lapilli from the main plume and fine ash elutriated from scoria flows emplaced on the western flank of the volcano. Our study also reveals that inappropriate grain-size data processing may produce misleading determination of eruptive type

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Section: Geological Setting and Recent Volcanic Activitymentioning

confidence: 99%

Section: Geological Setting and Recent Volcanic Activitymentioning

confidence: 99%

Section: Geological Setting and Recent Volcanic Activitymentioning

confidence: 99%

Section: Pyroclastic Flow Depositsmentioning

confidence: 99%

See 2 more Smart Citations

Causes and consequences of bimodal grain-size distribution of tephra fall deposited during the August 2006 Tungurahua eruption (Ecuador)

et al. 2011

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“…This volcano has continued its eruptive activity since 1999, in which major eruptions were characterized by vulcanian and strombolian eruptive styles and were accompanied by pyroclastic flows (Hall et al 1999(Hall et al , 2013Samaniego et al 2011;Mothes et al 2015). There are five permanent broadband seismic stations at Tungurahua (Fig.…”

Section: Tremor Signalsmentioning

confidence: 99%

An approach to source characterization of tremor signals associated with eruptions and lahars

et al. 2015

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Tremor signals are observed in association with eruption activity and lahar descents. Reduced displacement (D R ) derived from tremor signals has been used to quantify tremor sources. However, tremor duration is not considered in D R , which makes it difficult to compare D R values estimated for different tremor episodes. We propose application of the amplitude source location (ASL) method to characterize the sources of tremor signals. We used this method to estimate the tremor source location and source amplitude from high-frequency (5-10 Hz) seismic amplitudes under the assumption of isotropic S-wave radiation. We considered the source amplitude to be the maximum value during tremor. We estimated the cumulative source amplitude (I s ) as the offset value of the timeintegrated envelope of the vertical seismogram of tremor corrected for geometrical spreading and medium attenuation in the 5-10-Hz band. For eruption tremor signals, we also estimated the cumulative source pressure (I p ) from an infrasonic envelope waveform corrected for geometrical spreading. We studied these parameters of tremor signals associated with eruptions and lahars and explosion events at Tungurahua volcano, Ecuador. We identified two types of eruption tremor at Tungurahua: noise-like inharmonic waveforms and harmonic oscillatory signals. We found that I s increased linearly with increasing source amplitude for lahar tremor signals and explosion events, but I s increased exponentially with increasing source amplitude for inharmonic eruption tremor signals. The source characteristics of harmonic eruption tremor signals differed from those of inharmonic tremor signals. We found a linear relation between I s and I p for both explosion events and eruption tremor. Because I p may be proportional to the total mass involved during an eruption episode, this linear relation suggests that I s may be useful to quantify eruption size. The I s values we estimated for inharmonic eruption tremor were consistent with previous estimates of volumes of tephra fallout. The scaling relations among source parameters that we identified will contribute to our understanding of the dynamic processes associated with eruptions and lahars. This new approach is applicable in analyzing tremor sources in real time and may contribute to early assessment of the size of eruptions and lahars.

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Regional controls on magma ascent and storage in volcanic arcs

Chaussard

Amelung

2014

Geochem. Geophys. Geosyst.

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Understanding the controls for magma ascent and storage depth is important for volcanic hazard assessment. Regional differences in the depths of magma storage between volcanic arcs suggest that the settings of subduction zones and of overriding plates influence how magma ascends through the crust. Here we use a compilation of data for 70 volcanoes in 15 volcanic regions to better understand the geodynamic controls on magma storage. We describe the subduction system, which consists of the subducting slab, the mantle wedge, and the upper plate with 12 parameters encompassing the kinematics of the subduction, the structure and geometry of the slab, the timing of the subduction, the thermal structure of the slab, the upperplate crustal structure, its stress regimes, and its thermal structure. We find that the magma reservoir depths correlate with the upper-plate crustal structure and with the stress regimes. Shallow reservoirs (<5 km depths) are 52% more common in young Tertiary crust than in old Precambrian crust and 42% more common in thin crust (<25 km) than in thick crust (>45 km). Similarly, shallow magma reservoirs are 33-69% more common in extensional and strike-slip stress regimes that in compressional regimes. This illustrates the effect of buoyancy for magma ascent as well as the importance of stress regime and preexisting structures.

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Petrological analysis of the pre-eruptive magmatic process prior to the 2006 explosive eruptions at Tungurahua volcano (Ecuador)

Cited by 108 publications

References 54 publications

Causes and consequences of bimodal grain-size distribution of tephra fall deposited during the August 2006 Tungurahua eruption (Ecuador)

Causes and consequences of bimodal grain-size distribution of tephra fall deposited during the August 2006 Tungurahua eruption (Ecuador)

An approach to source characterization of tremor signals associated with eruptions and lahars

Regional controls on magma ascent and storage in volcanic arcs

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