Pyroclastic flow generated by crater-wall collapse and outpouring of the lava pool of Arenal Volcano, Costa Rica

Alvarado, Guillermo E.; Soto, Gerardo J.

doi:10.1007/s00445-001-0179-9

Cited by 49 publications

(71 citation statements)

References 17 publications

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“…1), in Costa Rica, is one of the 16 most active volcanoes in the world (Simkin and Siebert, 2000). It has been notable for the production of pyroclastic flows since the volcano renewed its activity in 1968, following several centuries of dormancy (Melson and Sáenz, 1973;Borgia et al, 1988;Alvarado and Soto, 2002). The 1968 eruption and its disastrous effects are discussed in three widely quoted papers Sáenz, 1968, 1973;Minakami et al, 1969), and typified in several textbooks as an Ultra-Vulcaniantype eruption (Williams and McBirney, 1979) or Vulcanian type (Sigurdsson et al, 2000;Schmincke, 2004).…”

Section: Introductionmentioning

confidence: 99%

The 1968 andesitic lateral blast eruption at Arenal volcano, Costa Rica

Alvarado

Soto

Schmincke

et al. 2006

Journal of Volcanology and Geothermal Research

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The magmatic andesitic eruption of Arenal volcano on July 29-31, 1968, after centuries of dormancy, produced three new fissural craters (A, B and C) on its western flank and a multilayered pyroclastic deposit emplaced by complex transport mechanisms. The explosions were initially triggered by a volatile oversaturated (4-7 wt.% H 2 O) magma. Several lines of evidences suggest a small blast surge, where a wood-rich pyroclastic deposit was emplaced as a ground layer, followed by several units of coarse-grained (Md Φ between −0.65 and −5.40) tephra deposits (LU: lapilli units, DAU: double ash units). LU-1, -2, -3, DAU-1 and -2 consist of unconsolidated and well-to poorly sorted vesiculated bombs and lapilli of andesite, some blocks, ash and shredded wood. The individual units are possibly correlated with the major explosions of July 29. The thickness of the deposits decreases with the distance from the volcano from 5.6 m to a few centimeters. On average, 90% of the components are juvenile (10% dense andesite and 90% vesicular). These coarse-grained beds were deposited in rapid succession by a complex transport process, involving normal fallout, strong ballistic trajectories with a lateral hot (∼400°C) blast surge (LU, equivalent to A 1 ). Ballistic and coarse tephra sprayed in a narrow (85°) area within about 5.5 km from the lowest crater, and a high (ca. 10 km) eruption column dispersed airfall fine lapilli-ash > 100 km from the volcano. Ashcloud forming explosions, producing thin pyroclastic surge and muddy phreatomagmatic fallout deposits (FLAU, equivalent to A 2 and A 3 ), closed the blast surge sequence. The successive explosions on July 30-31 mainly produced block and ash flows, and widely dispersed ash fall. The total volume of pyroclastic material is calculated as 25.8 ± 5.5 × 10 6 m 3 (9.4 ± 2.0 × 10 6 m 3 DRE). A model is proposed to explain the peculiarities of the formation, transportation and emplacement of the blast deposits. The intrusion of the presumed andesitic cryptodome possibly happened through an active thrust fault, favoring not only the formation of the lowest crater A, but also the low-angle explosive events. Prior to the eruption, several minerals were settling to the bottom of the magma chamber as is suggested by the increase of incompatible elements towards the bottom of the stratigraphic section. The major elements indicate that some crystal redistribution occurred and the maximum concentration of Al 2 O 3 , and Eu, and Sr support plagioclase enrichment in early phases of the eruption (top of LU-1 and DAU-1). From the about 20 recognized prehistoric and historic blast deposits in the world, approximately half were produced by sector collapse of the volcano and the other half by sudden decompression of cryptodomes or lava-dome collapses. The recent blasts (1888-1990s) ARTICLE IN PRESSdozen described for the previous 50 ka. Therefore, the adequate recognizers of the blast facies in the cone-building lithofacies, especially for small stratocones as described here, can help in und...

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Section: Introductionmentioning

confidence: 99%

The 1968 andesitic lateral blast eruption at Arenal volcano, Costa Rica

Alvarado

Soto

Schmincke

et al. 2006

Journal of Volcanology and Geothermal Research

Self Cite

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“…The activity in the period of 1984-1998 was characterized by mixed strombolian and effusive eruptions from the highest crater, which is about 200 m from the summit (Alvarado and Soto, 2002;Wadge et al, 2006). Although the discharged magma is basaltic andesite and sometimes forms a lava pool in the crater, its viscosity is sometimes large enough to allow the generation of pyroclastic flows (Alvarado and Soto, 2002). Hagerty et al (2000) were the first to report SHT-SAHT switching.…”

Section: Comparison With Other Casesmentioning

confidence: 99%

Switching from seismic to seismo-acoustic harmonic tremor at a transition of eruptive activity during the Shinmoe-dake 2011 eruption

2013

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This paper reports a sequence of harmonic tremor observed during the 2011 eruption of Shinmoe-dake volcano, Kyushu, Japan. The main eruptive activity started with subplinian eruptions, followed by lava effusion. Harmonic tremor was observed as seismic waves during the final stage of the effusive eruption. The tremor observed at this stage had unclear and fluctuating harmonic modes. In the atmosphere, however, many impulsive acoustic waves indicating small surface explosions were observed. When effusion stopped and explosive degassing began, harmonic tremor was observed as acoustic waves in the air and in the seismic data, and the harmonic modes became clearer and more stable. This transition in the character of the harmonic tremor coincided with rapid deflation of the lava that had accumulated in the crater. Based on these observations, and laboratory experiments reproducing the features of the wave fields, it is concluded that the harmonic tremor sequence at Shinmoe-dake was generated by gas flowing through channels in the gradually solidifying lava. Comparing our results with the few cases of similar transition observed at other volcanoes, we expect that the transition indicates changes in magma rheology and degassing conditions in the crater, and therefore of changes in eruptive activity.

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“…Each successive event formed flows that had progressively shorter run out distances. Deposits formed by the July 1975 pyroclastic flows are between 8 and 10 m thick (Alvarado and Soto 2002). The Tabacon hot springs bathing resort is built on the 1975 pyroclastic flow deposits (Fig.…”

Section: Explosive Activity At Arenalmentioning

confidence: 99%

“…2). These explosions have been described as being strombolian (Alvarado and Soto 2002) or, rarely, vulcanian (e.g. SEAN 1988b).…”

Section: Introductionmentioning

confidence: 99%

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Explosive activity and generation mechanisms of pyroclastic flows at Arenal volcano, Costa Rica between 1987 and 2001

et al. 2005

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Explosive activity at Arenal and associated tephra fall that has occurred over the 14-year period from 1987-2001 is described. Explosions have been notably variable in both frequency and size. A marked decrease in both frequency and quantity of tephra fallout occurred in early 1998 until the end of 2001. Grainsize distributions of cumulative tephra samples collected once a month are typically bimodal. Aggregation causing premature fallout of fine ash and possibly fallout from ash plumes produced by pyroclastic flows are considered responsible for the bimodality of fallout. Scanning electron microscopy of the glass component of tephra from single explosions show predominantly blocky and blocky/fluidal clast types, interpreted as being the product of vulcanian type explosions. Fragmentation of a mainly rigid, degassed magma body, and a minor molten component is inferred for these explosions. Pyroclastic flows were produced either associated with the larger explosions by a mechanism of column collapse (1987)(1988)(1989)(1990), or unrelated to explosions by partial collapse of the crater wall (1993, 1998, 2000, 2001). Pyroclastic flow activity has migrated from west to north during the period reported. Pyroclastic flow deposits are variable in the quantity of juvenile material and any associated surge component. Large juvenile blocks were partially molten on emplacement and many have a typical cauliform texture. Blocks with both juvenile and lithic textures indicate that at the summit magma was in intimate contact with the pre-existing edifice, rather than as a simple open crater or lava pool. Crater wall collapse may have been promoted by the reduction in explosive activity, which has increased the lava accumulation at the summit and in turn increased instability of the summit region. Thus although explosive activity has waned, if the lava output is maintained, the hazard of pyroclastic flows is likely to continue.

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Pyroclastic flow generated by crater-wall collapse and outpouring of the lava pool of Arenal Volcano, Costa Rica

Cited by 49 publications

References 17 publications

The 1968 andesitic lateral blast eruption at Arenal volcano, Costa Rica

The 1968 andesitic lateral blast eruption at Arenal volcano, Costa Rica

Switching from seismic to seismo-acoustic harmonic tremor at a transition of eruptive activity during the Shinmoe-dake 2011 eruption

Explosive activity and generation mechanisms of pyroclastic flows at Arenal volcano, Costa Rica between 1987 and 2001

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