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| Titel |
Dynamics and functional model of the 2012–13 flank fissure eruption of Tolbachik volcano in Kamchatka, Russia |
| VerfasserIn |
Alexander Belousov, Marina Belousova, Benjamin Edwards |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250143180
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| Publikation (Nr.) |
 EGU/EGU2017-6881.pdf |
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| Zusammenfassung |
| The 2012–13 flank fissure eruption of Tolbachik in Kamchatka Peninsula lasted more than nine months and discharged ~0.55 cub.km DRE of basaltic trachyandesite magma. It is one of the most voluminous historical eruptions of mafic magma at subduction-related volcano globally, and is the second largest in Kamchatka. We present a broad overview of the eruption as well as a model for the magma storage and transport system of Plosky Tolbachik Volcano. The 2012–13 eruption was preceded by five months of elevated seismicity and ground inflation, both of which peaked a day before the eruption commenced on 27 November 2012. The batch of high-Al magma ascended from depths of 5-10 km; its apical part contained 54–55 wt.% SiO2, and the main body 52–53 wt.% SiO2. The eruption started by the opening of a 6 km-long radial fissure on the southwestern slope of the volcano that fed multi-vent phreatomagmatic and magmatic explosive activity, as well as intensive effusion of lava with an initial discharge of 440 cub.m/s. After 10 days the eruption continued only at the lower part of the fissure, where explosive and effusive activity of Hawaiian–Strombolian type occurred from a lava pond in the crater of the main growing scoria cone. The discharge rate for the nine month long, effusion-dominated eruption gradually declined from 140 to 18 cub.m/s and formed a compound lava field with a total area of ~36 sq.km; the effusive activity evolved from high-discharge channel-fed 'a'a lavas to dominantly low-discharge tube-fed pahoehoe lavas. On 23 August, the effusion of lava ceased and the intra-crater lava pond drained. Weak Strombolian-type explosions continued for several more days on the crater bottom until the end of the eruption around 5 September 2013.
The volcanic system, comprising the stratovolcano Plosky Tolbachik and its two radial volcanic rifts, produces alternating eruptions of two genetically related magma types: high-Al basalt (eruptions at the summit and along both rift zones) and high-Mg basalt (eruptions only along the southwest rift). The high-Al magma ascends to the surface from a magma storage zone at a depth of about 5 km below the summit of Plosky Tolbachik. During the 2012–13 eruption the high-Al magma first ascended along the central conduit of the volcano. Then the feeding dyke deviated from the conduit and propagated sub-horizontally along the southwest rift at a depth about 1 km below sea level. The 1975–76 Southern Breakthrough of the volcano was fed in a similar way. In contrast, the 1975–76 Northern Breakthrough of the volcano was fed by vertical dyke of high-Mg magma that ascended to the ground surface from the magma storage zone located directly below the area of the Breakthrough at a depth of approximately 20 km. |
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