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| Titel |
Glacial influence on caldera-forming eruptions |
| VerfasserIn |
Adelina Geyer, Ilya Bindeman |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250035694
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| Zusammenfassung |
| Investigation of Ar-Ar, U-Pb, and 14C ages of caldera-forming eruptions for the past million
years in glaciated arc of Kamchatka has lead to observations that the majority of
large-volume ignimbrites, which are associated with the morphologically-preserved calderas,
correspond in time with “maximum glacial” conditions. The latter are defined as the highest
δ18O foraminifera values on the N Pacific SPECMAP stack. Additional evidence comes from
clustering Kamchatka-derived marine ash layers with glacial moraines in DSDP cores. The
strongest field evidence comes from glaciated multi-caldera volcanoes that hosted thick
glacial ice caps. In this paper, we investigate how glacial load dynamics may alter
eruption frequency in such glaciated multicaldera volcanoes. We present results of
numerical simulations that include ice cap of different thickness (ranging from 0 to 1
km) on top of calderas of relevant sizes (5 to 40 km) with magma chambers at
different depths. We also study the effects of an asymmetric ice distribution, a variable
pre-caldera topography, glacial overpressure on volatiles solubility, and the subglacial
intracaldera hydrothermal system on changing mechanical properties of roof rock.
The results are: 1) Any ice cap retard ring-fall propagation and caldera formation;
2) Asymmetric distribution of ice plays no or minor role; 3) Glacial erosion of
part of volcanic edifice or interglacial edifice failure may promote ring fracture; 4)
hydrothermal system under an ice cap may have more acidic hydrothermal fluids leading to
more effective hydrothermal rotting of the intracaldera roof rocks; 5) short period
interstadial during maximal glaciation may play most important role in pressure
fluctuations/volatite saturation condition; 6) Arching influence of the ice cap on roof rock
may lead to ring fracture. Overall, the maximal glacial time represent the most dynamic
time in a multi-caldera volcano life promoting physical and chemical feedbacks. |
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