The kicking Jenny – or is she?

It seems this time Kick’em Jenny is going to do her name honor – today, 23 July 2015, an orange alert has been issued for the submarine volcano.

Kick ’em Jenny and newly identified craters and domes discovered in March 2003. (Image courtesy of NOAA and Seismic Research Institute, 2003 [published in GVN Bulletin]).

The Seismic Research Centre (SRC) of the University of the West Indies has issued an orange alert for the underwater volcano Kick’em Jenny, after strong and sustained signals were recorded in the early hours of this morning suggesting than an eruption could occur with less than 24-hours notice. Instruments monitoring the volcano, located 8km north of Grenada (12.3000° N, 61.6400° W), recorded strong, continuous activity between 1:25 a.m. and 3.am. Grenada, as well as St. Vincent and the Grenadines, Barbados and Trinidad & Tobago are particularly on alert. At the orange alert level, the SRC recommends that the governments of Grenada, St. Vincent, Barbados and Trinidad & Tobago should advise residents of evacuation routes, and put transportation on standby to facilitate evacuation in the event of a tsunami.

Kick’em Jenny, on the steep inner western slope of the Lesser Antilles ridge, was discovered in 1939 when an explosive eruption broke the surface, producing ash columns that reached up to 300 meters above the sea surface (Devas, 1974). There have been at least 11 eruptions since then, with the most recent in 2001. The first detailed survey of the volcano in 1972 revealed a conical structure 1,300 meters high, constructed on the western flank of the arc. The summit crater was found to be at a depth of 190 meters and approximately 180 meters in diameter. The deepest point on Kick ’em Jenny’s crater floor lies at ~264 m depth.

Ocean ground investigation on Kick’em Jenny hydrothermal vents

Recent bathymetric surveys have shown evidence for a major arcuate collapse structure that was the source of a submarine debris avalanche that traveled more than 15 km to the west. Bathymetry also revealed another submarine cone to the SE, Kick ’em Jack, and submarine lava domes to its south. These and subaerial tuff rings and lava flows at Ile de Caille and other nearby islands may represent a single large volcanic complex. Numerous historical eruptions, mostly documented by acoustic signals, have occurred at Kick ’em Jenny since 1939, when an eruption cloud rose 275 m above the sea surface. Prior to the 1939 eruption, which was witnessed by a large number of people in northern Grenada, there had been no written mention of Kick ’em Jenny. Eruptions have involved both explosive activity and the quiet extrusion of lava flows and lava domes in the summit crater; deep rumbling noises have sometimes been heard onshore. Historical eruptions have modified the morphology of the summit crater.

The emission of large quantities of bubbles was observed in 1989 when the submersible Johnson Sealink entered the crater a few months after the 1988 eruption (SEAN 14:05).

A water column containing a significant proportion of rising gas bubbles results in a local lowering of the seawater’s density. (The rising bubbles displace some of the sea water, and at or near the sea surface they provide negligible support to the ship, thus resulting in a loss of buoyancy for ships passing over the volcano.) To account for this hazard, and the risk posed by ejecta, an exclusion zone 1.5 km in radius was created over the volcano (Shepherd, 2004).

UPDATES

UWI Scientific Advisory Jul.25.2015
Kick’em Jenny Update 1
Elevated seismic activity associated with Kick’em Jenny submarine volcano has continued since our last update. Following the hour long eruption signal which started at 01:42am on 23 July 2015 activity continued at an elevated level until 1:30pm. During the period midnight to 4:30pm on 23 July 2015 more than 400 events were recorded. The largest of these was of magnitude 3.3. Seismicity declined from 1:30pm to 5:30pm on 23 July but increased thereafter. At about 2:00am on Friday 24 July an explosion signal was recorded. This signal lasted for about an hour. T-phase from this event was recorded in Montserrat confirming the nature of the activity. The number of earthquakes declined during Friday with only 89 events recorded up to 4:00pm. Overnight this decline continued and between 4:00pm 24 July to 6:30am 25 July less than 20 earthquakes were detected. We will continue to monitor throughout the day to develop a better understanding of the current state of the system. The current alert level remains at Orange.

UWI Scientific Advisory  Jul.25.2015
Kick ’em Jenny Update 2
Activity associated with the Kick’em Jenny system continues to decrease. From the 20 events recorded between the period 4:00pm 24th July to 6:30am 25th July, the number of events recorded up to 8:00pm 25th (local time) has consisted of less than 10 below magnitude 2.0. A reconnaissance flight was conducted this afternoon with, volcanologist Dr. Frederic Dondin, one of two of the UWI-SRC team currently in Grenada. Nothing out of the ordinary was observed at the surface above the volcano. Additional instruments were also placed closer to the volcano which reduces the threshold magnitude of events associated with the Kick-‘em-Jenny system that can be identified. We will continue to monitor and update as data come to hand. The current alert level at Kick ’em Jenny still remains at Orange.

Source: http://www.uwiseismic.com/ScientificAdvisories.aspx

Enjoy! -GRANYIA

Sources:
– http://www.uwiseismic.com/NewsDetails.aspx?id=365
– http://www.uwiseismic.com/General.aspx?id=53
– http://volcano.si.edu/volcano.cfm?vn=360160

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