Shallowly driven fluctuations in lava lake outgassing (gas pistoning), Kīlauea Volcano
| Autor: | Einat Lev, W. A. Thelen, A.J. Sutton, Matthew R. Patrick, Tim R. Orr, David Fee |
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| Rok vydání: | 2016 |
| Předmět: |
Basalt
geography geography.geographical_feature_category 010504 meteorology & atmospheric sciences Lava Induced seismicity 010502 geochemistry & geophysics 01 natural sciences Outgassing Permeability (earth sciences) Geophysics Volcano Space and Planetary Science Geochemistry and Petrology Gas slug Earth and Planetary Sciences (miscellaneous) Dynamic pressure Petrology Geomorphology Geology 0105 earth and related environmental sciences |
| Zdroj: | Earth and Planetary Science Letters. 433:326-338 |
| ISSN: | 0012-821X |
| Popis: | Lava lakes provide ideal venues for directly observing and understanding the nature of outgassing in basaltic magmatic systems. Kīlauea Volcano's summit lava lake has persisted for several years, during which seismic and infrasonic tremor amplitudes have exhibited episodic behavior associated with a rise and fall of the lava surface (“gas pistoning”). Since 2010, the outgassing regime of the lake has been tied to the presence or absence of gas pistoning. During normal behavior (no gas pistoning), the lake is in a “spattering” regime, consisting of higher tremor amplitudes and gas emissions. In comparison, gas piston events are associated with an abrupt rise in lava level (up to 20 m), during which the lake enters a “non-spattering” regime with greatly decreased tremor and gas emissions. We study this episodic behavior using long-term multidisciplinary monitoring of the lake, including seismicity, infrasound, gas emission and geochemistry, and time-lapse camera observations. The non-spattering regime (i.e. rise phase of a gas piston cycle) reflects gas bubbles accumulating near the top of the lake, perhaps as a shallow foam, while spattering regimes represent more efficient decoupling of gas from the lake. We speculate that the gas pistoning might be controlled by time-varying porosity and/or permeability in the upper portions of the lava lake, which may modulate foam formation and collapse. Competing models for gas pistoning, such as deeply sourced gas slugs, or dynamic pressure balances, are not consistent with our observations. Unlike other lava lakes which have cyclic behavior that is thought to be controlled by deeply sourced processes, external to the lake itself, we show an example of lava lake fluctuations driven by cycles of activity at shallow depth and close to the lake's surface. These observations highlight the complex and unsteady nature of outgassing from basaltic magmatic systems. |
| Databáze: | OpenAIRE |
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