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| Titel |
Oscillatory degassing of a phonolite lava lake, Erebus volcano, Antarctica |
| VerfasserIn |
C. Oppenheimer  , P. Kyle, A. Lomakina, N. Kingsbury |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250025560
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| Zusammenfassung |
| Lava lakes provide windows into the magma networks that feed active volcanoes. Their
observation can provide important insights into magma transport and eruptive
styles. A few lava lakes, like that at Erebus volcano, Antarctica, have been
continuously active for decades. Such persistence suggests bidirectional magma
flow in the feeder conduit, driven by density contrasts arising from degassing.
However, few observations distinguish the manner in which gases separate
from magmas, undermining efforts to evaluate physical models for rheology
and eruptive behaviour. Using spectroscopic observations at Erebus, we show
that the gas plume emitted from its lava lake consists of two components: a
deep-sourced CO2-rich gas that percolates through permeable conduit magma,
and an H2O-rich gas exsolved near the surface. Thermal observations reveal
~10 min cycles in lava lake convection and heat output that are strikingly
phase-locked with cycles in gas composition and flux, suggesting similarities
with laboratory simulations. Our findings indicate unstable magma flow in
the upper conduit due to viscosity stratification, and exemplify the relative
roles of closed- and open-system degassing in persistently active volcanoes.
Since this interplay between degassing styles can be associated with abrupt
transitions in eruptive behaviour, the ability to discriminate gas sources in a
volcanic plume can contribute more widely to volcanic hazard assessment. |
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