This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

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Susan Kieffer can be contacted at s1kieffer at gmail.com

Tuesday, May 15, 2012

Monowai volcano: fast outpouring of magma observed over 5 days

Bathymetry of summit of Monowai Cone May/June 2011.
How fast can a volcano spew out magma? This is a question that has perplexed volcanologist for a very long time.  Recently a team of scientists, led by A.B. Watts of Oxford University,  conducting a routine bathymetric survey onboard the research vessel  SONNE, were fortunate enough to be in the proximity of Monowai seamount volcano when a dramatic eruption occurred.**  Monowai is located along the 2,500 km-long Tonga-Kermadec Arc, where a submarine volcano can be found approximately every 50 km.
Eruptive volume versus duration of magmatism for submarine volcanoes.
Monowai is not small. It is a 10-12 km-wide strato-volcanoe approximately 1 km high with a 7-10 km wide caldera in its summit, approximately 0.6 km deep. Since it was first discovered in 1944 it has had a history of activity (discoloured water emanations and seismic ity). On May 14, 2011, the scientific team observed gassy discoloured water on the summit of the Monowai Cone. Three days later, a swarm of seismic events began and lasted for 5 days. On June 1, after the seismic activity subsided, the ship returned and carried out a second survey of the cone. They found significant changes in depth at the volcano. The main differences were (1) an increase in depth of up to 18.8 meters attributed to collapse structures on the flanks of the volcano, and (2) a decrease in depth of up to 71.9 m due to growth by eruption of new lava flows. The most striking feature of the surveys was a new cone near the summit. From its dimensions (100 m diameter at its base, at least 40 m high), it appears that about 0.00875 cubic kilometres of magma was erupted, most likely during the 5-day swarm of seismic activity. Extrapolating these rates to annual output, Monowai joins Kilauea, Iceland, Montserrat, the Azores, Hawaii, and the Canary Islands withoutput on the order of 0.1 cubic kilometres per year.

**Reported in A.B. Watts, et al., Rapid rates of growth and collapse of Monowai submarine volcano in the Kermadec Arc, Nature Geoscience, Advance publication, doi: 10.1038/NGE01473, posted May 13, 2012. Featured on Geology.com on May 15, 2012.

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