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Cyclic eruptions and sector collapses at Monowai submarine volcano, Kermadec arc: 1998-2007

Cyclic eruptions and sector collapses at Monowai submarine volcano, Kermadec arc: 1998-2007
Cyclic eruptions and sector collapses at Monowai submarine volcano, Kermadec arc: 1998-2007
Repeated multibeam bathymetric surveys at Monowai Cone, a shallow submarine basaltic volcano and part of the Monowai Volcanic Center in the northern Kermadec arc, were conducted in 1998, 2004, and 2007. These surveys document dramatic depth changes at the volcano including negative changes up to ?176 m from two sector collapses and positive changes up to +138 m from volcanic reconstruction near the summit and debris avalanche deposits downslope of the slide scars. One sector collapse occurred on the SE slope between 1998 and 2004 with a volume of ?0.09 km3, and another occurred on the SW slope between 2004 and 2007 with a volume of ?0.04 km3. The volume of positive depth change due to addition of volcanic material by eruption is of the same order: ?0.05 km3 between 1998 and 2004 and ?0.06 km3 between 2004 and 2007. During these time intervals, monitoring by the Polynesian Seismic Network detected frequent T wave swarms at Monowai, indicative of explosive eruptive activity every few months. An unusual T wave swarm on 24 May 2002 was previously interpreted as the collapse event between the 1998 and 2004 surveys, but no similarly anomalous T waves were detected between 2004 and 2007, probably because the Polynesian Seismic Network stations were acoustically shadowed from the second slide event. We interpret that the sector collapses on Monowai are caused by the unstable loading of fragmental erupted material on the summit and steep upper slopes of the volcano (>20°). Moreover, there appears to be a cyclic pattern in which recurrent eruptions oversteepen the cone and periodically lead to collapse events that transport volcaniclastic material downslope to the lower apron of the volcano. Volumetric rate calculations suggest that these two processes may be more or less in equilibrium. The repeated collapses at Monowai are relatively modest in volume (involving only 0.1–0.5% of the edifice volume), have occurred much more frequently than is estimated for larger debris avalanches at subaerial volcanoes, and may be characteristic of how persistently active shallow submarine arc volcanoes grow.
sector collapse, debris avalanche, submarine eruptions, explosive volcanism, volcano morphology, landslide
1525-2027
Q10014
Chadwick, W.W.
0bfbcd74-c935-4d61-8925-577c5a70a496
Wright, I.C.
be2a8931-3932-4f1e-b387-43e3652bf3fc
Schwarz-Schampera, U.
0c455166-ac71-4c22-8a0e-acaf125679ba
Hyvernaud, O.
02e31b95-8eec-4890-811a-9925d8b1aa38
Reymond, D.
ca7147e3-f470-4d68-bdee-dc740a90a6f0
de Ronde, C.E.J.
1b9222e8-63bf-4ae0-bc66-c496bc5e3e5f
Chadwick, W.W.
0bfbcd74-c935-4d61-8925-577c5a70a496
Wright, I.C.
be2a8931-3932-4f1e-b387-43e3652bf3fc
Schwarz-Schampera, U.
0c455166-ac71-4c22-8a0e-acaf125679ba
Hyvernaud, O.
02e31b95-8eec-4890-811a-9925d8b1aa38
Reymond, D.
ca7147e3-f470-4d68-bdee-dc740a90a6f0
de Ronde, C.E.J.
1b9222e8-63bf-4ae0-bc66-c496bc5e3e5f

Chadwick, W.W., Wright, I.C., Schwarz-Schampera, U., Hyvernaud, O., Reymond, D. and de Ronde, C.E.J. (2008) Cyclic eruptions and sector collapses at Monowai submarine volcano, Kermadec arc: 1998-2007. Geochemistry, Geophysics, Geosystems, 9, Q10014. (doi:10.1029/2008GC002113).

Record type: Article

Abstract

Repeated multibeam bathymetric surveys at Monowai Cone, a shallow submarine basaltic volcano and part of the Monowai Volcanic Center in the northern Kermadec arc, were conducted in 1998, 2004, and 2007. These surveys document dramatic depth changes at the volcano including negative changes up to ?176 m from two sector collapses and positive changes up to +138 m from volcanic reconstruction near the summit and debris avalanche deposits downslope of the slide scars. One sector collapse occurred on the SE slope between 1998 and 2004 with a volume of ?0.09 km3, and another occurred on the SW slope between 2004 and 2007 with a volume of ?0.04 km3. The volume of positive depth change due to addition of volcanic material by eruption is of the same order: ?0.05 km3 between 1998 and 2004 and ?0.06 km3 between 2004 and 2007. During these time intervals, monitoring by the Polynesian Seismic Network detected frequent T wave swarms at Monowai, indicative of explosive eruptive activity every few months. An unusual T wave swarm on 24 May 2002 was previously interpreted as the collapse event between the 1998 and 2004 surveys, but no similarly anomalous T waves were detected between 2004 and 2007, probably because the Polynesian Seismic Network stations were acoustically shadowed from the second slide event. We interpret that the sector collapses on Monowai are caused by the unstable loading of fragmental erupted material on the summit and steep upper slopes of the volcano (>20°). Moreover, there appears to be a cyclic pattern in which recurrent eruptions oversteepen the cone and periodically lead to collapse events that transport volcaniclastic material downslope to the lower apron of the volcano. Volumetric rate calculations suggest that these two processes may be more or less in equilibrium. The repeated collapses at Monowai are relatively modest in volume (involving only 0.1–0.5% of the edifice volume), have occurred much more frequently than is estimated for larger debris avalanches at subaerial volcanoes, and may be characteristic of how persistently active shallow submarine arc volcanoes grow.

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Published date: 2008
Keywords: sector collapse, debris avalanche, submarine eruptions, explosive volcanism, volcano morphology, landslide

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Local EPrints ID: 63082
URI: https://eprints.soton.ac.uk/id/eprint/63082
ISSN: 1525-2027
PURE UUID: 442bb409-8552-42ce-88ed-260db29d583f

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Date deposited: 09 Sep 2008
Last modified: 13 Mar 2019 20:26

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Contributors

Author: W.W. Chadwick
Author: I.C. Wright
Author: U. Schwarz-Schampera
Author: O. Hyvernaud
Author: D. Reymond
Author: C.E.J. de Ronde

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