The shallow structure of Kīlauea caldera from high‐resolution Bouguer gravity and total magnetic anomaly mapping: Insights into progressive magma reservoir growth

Zurek, Jeffrey; Williams‐Jones, Glyn

doi:10.1002/jgrb.50243

Cited by 16 publications

(23 citation statements)

References 54 publications

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“…InSAR data spanning the same time interval indicate moderate surface displacements (both uplift and subsidence, <0.20 m) accompanying the gravity changes, also centered northeast of the Halema‘uma‘u Crater. This location is similar to the loci of gravity increase measured between 1975 and 2008 that was interpreted as the result of magma accumulation in a void space at ~1 km depth [ Johnson et al ., ] or within a volume created by the rifting of the summit [ Zurek and Williams‐Jones , ].…”

Section: Discussionmentioning

confidence: 99%

“…Filling of void space by magma is the preferred mechanism of previous studies, although different processes were invoked for the formation of the space [ Johnson et al ., ; Zurek and Williams‐Jones , ]. Johnson et al .…”

Section: Discussionmentioning

confidence: 99%

“…Unlike the south caldera source, the shallow Halema‘uma‘u reservoir experienced a large mass increase during 1975–2008, but the lack of coincident inflation led Johnson et al . [] to propose that magma was filling subsurface void space and Zurek and Williams‐Jones [] to speculate that rifting of the summit led to additional magma accumulation without uplift. Summit deformation fluctuated after 2007, with inflation and deflation tied to changes in ERZ eruptive activity [ Poland et al ., , ; Lundgren et al ., ].…”

Section: Kīlauea Volcanomentioning

confidence: 99%

“…Campaign gravity and leveling data spanning the 29 November 1975 M w 7.7 Kalapana earthquake revealed that mass loss beneath the summit due to drainage of magma into Kīlauea's rift zones was larger than expected given the measured surface subsidence, implying the creation of void space [ Dzurisin et al ., ; Jachens and Eaton , ]. Subsequent surveys, extending through 2008, indicated a steady mass gain (residual gravity increase up to 450 μGal during 1975–2008) accompanied by subsidence (maximum of almost 2 m) near Halema‘uma‘u Crater within Kīlauea Caldera, which suggests filling of void space by magma [ Johnson et al ., ] or accommodation of additional magma volume by rifting of the summit [ Zurek and Williams‐Jones , ]. Since March 2008, a new long‐term eruption has been occurring at Kīlauea's summit, and a fissure eruption interrupted the ongoing (since 1983) east rift zone (ERZ) eruption in March 2011 (Figure ).…”

Section: Introductionmentioning

confidence: 99%

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Gravity changes and deformation at Kīlauea Volcano, Hawaii, associated with summit eruptive activity, 2009–2012

et al. 2014

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Analysis of microgravity and surface displacement data collected at the summit of Kīlauea Volcano, Hawaii (USA), between December 2009 and November 2012 suggests a net mass accumulation at 1.5 km depth beneath the northeast margin of Halema'uma'u Crater, within Kīlauea Caldera. Although residual gravity increases and decreases are accompanied by periods of uplift and subsidence of the surface, respectively, the volume change inferred from the modeling of interferometric synthetic aperture radar deformation data can account for only a small portion (as low as 8%) of the mass addition responsible for the gravity increase. We propose that since the opening of a new eruptive vent at the summit of Kīlauea in 2008, magma rising to the surface of the lava lake outgasses, becomes denser, and sinks to deeper levels, replacing less dense gas-rich magma stored in the Halema'uma'u magma reservoir. In fact, a relatively small density increase (<200 kg m À3) of a portion of the reservoir can produce the positive residual gravity change measured during the period with the largest mass increase, between March 2011 and November 2012. Other mechanisms may also play a role in the gravity increase without producing significant uplift of the surface, including compressibility of magma, formation of olivine cumulates, and filling of void space by magma. The rate of gravity increase, higher than during previous decades, varies through time and seems to be directly correlated with the volcanic activity occurring at both the summit and the east rift zone of the volcano.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Kīlauea Volcanomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Gravity changes and deformation at Kīlauea Volcano, Hawaii, associated with summit eruptive activity, 2009–2012

et al. 2014

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“…Each mechanism has a different expected gravitational field; therefore, the processed gravity data should enable us to discriminate between these hypotheses. If the Nīnole Hills were the location of a centralized proto‐volcano summit, the expected gravity signal would be circular and centered above a dense intrusive complex [e.g., Zurek and Williams‐Jones , ]. The measured gravity field cannot exclude a protovolcano summit as it appears circular; however, the Bouguer gravity anomaly centered on the Nīnole Hills is at least 5 km in length (Figure ), may extend further to the northeast, and 3‐D inversions allude to a connection with the SWRZ at depth at its SW extent, suggesting a more elongate structure.…”

Section: Formational Mechanismsmentioning

confidence: 99%

The origin of Mauna Loa's Nīnole Hills: Evidence of rift zone reorganization

Zurek

Williams‐Jones

Trusdell

et al. 2015

Geophys. Res. Lett.

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In order to identify the origin of Mauna Loa volcano's Nīnole Hills, Bouguer gravity was used to delineate density contrasts within the edifice. Our survey identified two residual anomalies beneath the Southwest Rift Zone (SWRZ) and the Nīnole Hills. The Nīnole Hills anomaly is elongated, striking northeast, and in inversions both anomalies merge at approximately −7 km above sea level. The positive anomaly, modeled as a rock volume of ~1200 km3 beneath the Nīnole Hills, is associated with old eruptive vents. Based on the geologic and geophysical data, we propose that the gravity anomaly under the Nīnole Hills records an early SWRZ orientation, now abandoned due to geologically rapid rift‐zone reorganization. Catastrophic submarine landslides from Mauna Loa's western flank are the most likely cause for the concurrent abandonment of the Nīnole Hills section of the SWRZ. Rift zone reorganization induced by mass wasting is likely more common than currently recognized.

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Dissecting a Zombie: Joint analysis of density and resistivity models reveals shallow structure and possible sulfide deposition at Uturuncu Volcano, Bolivia

MacQueen

Gottsmann

Pritchard

et al. 2021

Preprint

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The recent identification of unrest at multiple volcanoes that have not erupted in over 10 kyr presents an intriguing scientific problem. How can we distinguish between unrest signaling impending eruption after kyr of repose and non-magmatic unrest at a waning volcanic system? After ca. 250 kyr without a known eruption, in recent decades Uturuncu volcano in Bolivia has exhibited multiple signs of unrest, making the classification of this system as "active", "dormant", or "extinct" a complex question. Previous work identified anomalous low resistivity zones at <10 km depth with ambiguous interpretations. We investigate subsurface structure at Uturuncu with new gravity data and analysis, and compare these data with existing geophysical data sets. We collected new gravity data on the edifice in November 2018 with 1.5 km spacing, ±15 μGal precision, and ±5 cm positioning precision, improving the resolution of existing gravity data at Uturuncu. This high quality data set permitted both gradient analysis and full 3-D geophysical inversion, revealing a 5 km diameter, positive density anomaly beneath the summit of Uturuncu (1.5-3.5 km depth) and a 20 km diameter arc-shaped negative density anomaly around the volcano (0.5-7.5 depth). These structures often align with resistivity anomalies previously detected beneath Uturuncu, although the relationship is complex, with the two models highlighting different components of a common structure. Based on a joint analysis of the density and resistivity models, we interpret the positive density anomaly as a zone of sulfide deposition with connected brines, and the negative density arc as a surrounding zone of hydrothermal alteration. Based on this analysis we suggest that the unrest at Uturuncu is unlikely to be pre-eruptive. This study shows the value of joint analysis of multiple types of geophysical data in evaluating volcanic subsurface structure at a waning volcanic center.

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The shallow structure of Kīlauea caldera from high‐resolution Bouguer gravity and total magnetic anomaly mapping: Insights into progressive magma reservoir growth

Cited by 16 publications

References 54 publications

Gravity changes and deformation at Kīlauea Volcano, Hawaii, associated with summit eruptive activity, 2009–2012

Gravity changes and deformation at Kīlauea Volcano, Hawaii, associated with summit eruptive activity, 2009–2012

The origin of Mauna Loa's Nīnole Hills: Evidence of rift zone reorganization

Dissecting a Zombie: Joint analysis of density and resistivity models reveals shallow structure and possible sulfide deposition at Uturuncu Volcano, Bolivia

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