Scientists find volcanic craters off Grenada

The University of the West Indies
seismic research unit

After ten days of intense research aboard the National Oceanic and Atmospheric Administration (NOAA) R/V Ronald H. Brown in March, 2003, scientists have discovered three volcanic craters and two cones near the Kick ‘em Jenny submarine volcano. The detailed oceanographic survey and sampling of the volcano was funded by a grant from NOAA, and conducted by a joint team of scientists from the Seismic Research Unit of the University of the West Indies (UWI), the University of Rhode Island (URI) and NOAA.

The scientists are as yet unable to confirm whether or not these newly recognised craters are in fact separate live volcanoes. At a press conference in Grenada following the cruise Chief Scientist on the project Professor Haraldur Sigurdsson (URI) said that “We know of no historical eruptions from these craters. I suspect that they may be extinct. We will use chemical analysis of the rocks to tell whether these are separate volcanoes or not. If the rocks from the new craters are of the same chemistry as Kick ‘em Jenny then they are being fed from the same source. We will need to investigate this further”. The largest of these previously unrecognised volcanoes has been tentatively named ‘Kick ‘em Jack’.

Kick 'em Jenny is located 8km north of Grenada and it provides scientists with a unique natural laboratory to study the activity at a shallow submarine volcano that will one day emerge to form a new volcanic island. It is the only 'live' submarine volcano in the West Indies known to scientists and it has erupted at least 12 times since 1939. The last major eruption was 4th - 6th December, 2001. It is the most intensively monitored volcano in the Eastern Caribbean and probably the most intensively monitored submarine volcano in the world.

Although Kick ‘em Jenny has been surveyed at least eleven times since 1962, this cruise was the most detailed study to date. The scientists worked continuously on board NOAA’s flagship vessel Ronald H. Brown using state of the art equipment to conduct multi-disciplinary research which included the examination of aspects of submarine eruption style, magmatic evolution, hazards, influence on biological activity, and potential hydrothermal mineralization. For the first time ever an unmanned submarine was sent into the crater of Kick ‘em Jenny and was able to collect many rock and biological samples, and take fascinating video footage of the area in and outside the crater.

The recent cruise confirmed many of the results of a previous NOAA research cruise (March 2002) and also made some new discoveries. The crater of Kick 'em Jenny is almost perfectly circular and has a diameter of approximately 350 m. The centre of the crater is at 12.3004 °N 61.6378 °W. The highest point on the crater rim is at 61.6398 °W 12.3004 °N and is 180 m below sea level. The depth from the highest point on the crater rim to the lowest point of the crater floor is about 80 m. The crater is breached to the northeast. No dome is present within the crater, the floor of which is essentially smooth and featureless with the exception of an inner crater located in the northwestern quadrant of the main crater. This inner crater is elliptical in shape and is approximately 100 m long by 50 m wide and up to 50 m deep. Kick ‘em Jenny sits within a much bigger horseshoe shaped depression which extends at least 20 km to the west of the volcano and widens downslope from about 5 km to 10 km. A sequence of debris avalanche deposits were discovered within the depression, indicating that a large volcanic collapse event occurred here in the past.

Aside from the exciting discoveries of the ‘new’ craters and the debris avalanche deposit, scientists also discovered that Kick ‘em Jenny was continuously releasing gas bubbles from numerous fumaroles (steam vents) within the inner crater. This finding confirms previous suspicions that the volcano is actively degassing. This degassing can occur during or between eruptions and it can significantly lower the density of the water, thereby posing a serious danger to shipping. For the past 2 years the Seismic Research Unit has been working with the Grenadian government to enforce a 1.5 km exclusion zone around the summit of Kick ‘em Jenny. Unfortunately, this exclusion zone is not observed by many pleasure boats. In fact, during the recent research cruise scientists aboard the Ronald H. Brown observed many yachts within the exclusion zone and some sailed so close to the summit region of the volcano that they disrupted scientific work.

In addition to the geology, scientists also collected impressive biological samples from the volcano. Biologist at URI’s Graduate School of Oceanography, Dr. Karen Wishner commented at the press conference that “There is quite a special biological community there which is significant not just to Grenada but to international science because these are the first shallow vent communities found.” Shallow submarine active craters such as Kick ‘em Jenny provide a unique biological environment and it is quite possible to find life forms here that cannot be found elsewhere in the world.

The principal investigators on the cruise were Professor John Shepherd (UWI), Professor Haraldur Sigurdsson (URI), Professor Steve Carey (URI) and Dr. Doug Wilson (NOAA). The scientists collected much more data during the cruise than expected and they hoped to publish their findings before the end of the year. Sigurdsson ended the post-cruise press conference by commenting that “We continue to be amazed and puzzled by this volcano. We are thankful to the people of Grenada for allowing us to conduct this study and we hope to find additional funding for further research.”

Kick ‘em Jenny is currently at Alert Level Yellow, which requires a 1.5 km radius exclusion zone around the summit. Foar information on the Alert Levels for Kick ‘em Jenny together with more details on the recent cruise please visit www.uwiseismic.com.

For more information contact:
Jan Lindsay - Volcanologist
Stacey Edwards – Education & Outreach Coordinator
Seismic Research Unit
The University of the West Indies
St. Augustine Trinidad W.I.
staceyedwards@uwiseismic.com