Bathymetric time-lapse study of the Kick'em Jenny submarine volcano

The Kick'em Jenny submarine volcano saw its alert level increase on March 12, 2018;

But since his first explosive eruption observed in 1939, he remained very active.

The West Indies University (UWI) presented a list of major events.

A research, published March 13 in AGU journal / "Geochemistry, Geophysics, Geosystems", opens a new vision on the world of submarine volcanoes.

Since the first eruption in 1939, Kick'em Jenny Volcano (KeJ) has been the source of 13 episodes of T-phase signals. These distinctive seismic signals, which often coincide with increased seismicity of body waves, are interpreted as extrusive eruptions. They occurred with a recurrence interval of about a decade, but direct confirmation of volcanism was rare.

By conducting new bathymetric surveys in 2016 and 2017 and reprocessing 4 sets of 30-year historical data, the study presents a clearer picture of KeJ's development over time.

Currently, remote sensing of underwater eruptions relies heavily on phase T identification on regional hydrophones and seismometers. These distinctive hydro-acoustic signals can be produced by underwater earthquakes or by the interaction between water and fresh magma.

At KeJ, volcanic T-phase arrivals (which are assumed to indicate underwater eruptions) differ from signals of purely seismic origin due to their low frequency, impulsive appearance and duration (often several tens of seconds), similar signals tremor during periods of high activity (Lindsay et al., 2005). They also lack associated P and S wave arrivals, as would be expected from a signal with an earthquake source.

A correlation between the T-phase episodes was made with the morphological changes of the volcano: during the observation period, 7.09 million m³ of materials were added by constructive volcanism, but five times this amount was lost due to landslides.

Six bathymetric surveys over the period 1985-2017 revealed major morphological changes, the association of T-phase signals to both landslides and extrusive volcanism, and the importance of bathymetry over time for good monitoring of submarine volcanism.

Kick'em Jenny magma is usually a type of alkaline basalt with a mineral composition that indicates that it comes from the lower crust. Sigurdsson (1973) has shown that all the volcanoes of the West Indies arc above a subduction zone of two lithospheric plates. The activity of these volcanoes is the result of the gradual drift towards the west of a plate and its thrust under the adjacent plate.

Sampling of the crater and flanks during a multibeam survey by the NOAA research vessel, Ronald H. Brown, revealed that the dominant products of the volcano were pyroclastic deposits and pillow lavas of amphibole-rich basalts and basaltic andesites.

Sources:

- AGU - "G3" - 30 Years in the Life of an Active Submarine Volcano: A Time-Lapse Bathymetry Study of the Kick-'em-Jenny Volcano, Lesser Antilles - R. W. Allen & al / 13.03.2018

- NOAA Ocean Explorer - Geology of the Kick'em Jenny Volcano - Debby Kay, NOAA Research Web Coordinator