Relationships Between Subsurface Processes and Eruptive Products at Maar-diatreme Volcanoes Using Numerical Modeling and Tephra Ring Componentry
Abstract
Diatremes represent a unique example of a volcanic plumbing system in which the physical characteristics of the system control eruption dynamics, but in turn, the eruption dynamics greatly dictate how the diatreme evolves. As a result, interpreting surface deposits such as tephra rings is difficult in the context of the whole volcano system. Here we present a novel application of multiphase numerical modeling to simulate intra-diatreme explosions and their effects on transport and mixing length scales. This and previous work have shown that whether an explosion erupts material out of the diatreme depends on several variables, but especially the depth and energy of the explosion. Explosions deeper than 250 m are unlikely to erupt unless extremely large amounts of magma and water are involved. Erupted material at maar-diatreme volcanoes is therefore mostly sourced from the upper-most part of the diatreme. Our modeling shows that following an explosion, the material immediately surrounding and overlying the explosion site is propelled toward the surface via debris jets, which are imperfectly coupled gas-solid mixtures. As the debris jet ascends, material elsewhere in the diatreme undergoes substantial subsidence. This subsidence can be responsible for long residence times of clasts in the diatreme, which together with other factors such as "non-erupting" explosions, can bias a simple interpretation of tephra ring deposits (i.e. the presence of a certain lithology is indicative of the depth at which the eruption originated from). In light of these findings, tephra ring componentry from Dotsero Volcano (Colorado, USA) is compared to volume estimates of the well-constrained subsurface geology to estimate the proportions of different country rock units that might preside in the diatreme. These data in conjunction with different modeling scenarios elucidate intra-diatreme processes such as debris jet activity and their role in forming surface deposits.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.V53C3093S
- Keywords:
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- 8419 Volcano monitoring;
- VOLCANOLOGYDE: 8434 Magma migration and fragmentation;
- VOLCANOLOGYDE: 8439 Physics and chemistry of magma bodies;
- VOLCANOLOGYDE: 8486 Field relationships;
- VOLCANOLOGY