The temperature of the body of sea water above Kick-‘em-Jenny is generally no different to that of the seawater surrounding the volcano. Inside the crater of the volcano, however, at depths of about 260 m below sea level, there are areas where the water temperature is elevated relative to the surrounding seas. During the March 2003 NOAA research cruise over Kick ‘em Jenny scientists discovered numerous steam vents within the crater that may have temperatures of up to 150 ˚C. These hydrothermal venting undoubtedly heats up surrounding waters. The presence of zones of hot water within the crater was also suggested in 1989, when a manned research submersible experienced a problem during a dive on Kick ‘em Jenny. As the submersible passed over the crater rim and into the open crater, it entered a zone of sudden updraft and the craft was rapidly lifted towards the surface. The pilot claimed he thought they had encountered a pool or column of warmer water and the updraft carried them towards the surface.
Kick-‘em-Jenny is a relatively young volcano, and it seems likely that it will continue to erupt in the future, eventually forming a shoal and then a new island. We do not know how long it will take for the volcano to grow to the surface. The best-studied example of underwater dome growth in the West Indies occurred at the Soufriere volcano in St. Vincent in 1971. On that occasion a dome began to grow at the bottom of the 175 metre-deep crater lake in early October 1971 and reached the surface in late September 1972. By analogy with this episode we would expect a period of almost a year of steady effusive eruption before Kick-’em -Jenny breaks the surface. This represent the fastest growth scenario. It is also possible that the volcano could grow step-wise towards the surface, with long periods of non-growth interspersed with short periods of growth. This would take much longer, e.g. tens to hundreds or even thousands of years.
Kick-‘em-Jenny does NOT appear to be growing towards the surface of the sea, although until recently, this was thought to be the case. This interpretation was based on the fact that a depth measurement of 236 m obtained in 1962 was much greater than all subsequent depth measurements, which range from 190 to 160 m. However, a recent re-evaluation of the 1962 survey results by the staff of the Seismic Research Unit clearly shows that the boat missed the summit altogether during this early survey, and the value of 236 m in fact represents the depth to a point on the western flank of the volcano. The next survey, in 1966, revealed a depth to summit of 190 m and the most recent survey (March 2003) a depth to summit of 180 m. These depths are essentially the same, within error. We can therefore say that Kick-’em-Jenny has NOT grown any closer to the surface between 1962 and 2003. The summit (western crater rim) has consistently remained at about 180-190m below sea level, except during a period in the late 1970s to early 1980s when a dome grew in the crater, temporarily decreasing the depth to summit to 160 m, before the dome collapsed in the 1990 eruption.
It is of course possible that future eruptions at the volcano may result in a shallowing of the summit, and gradual (or even rapid) growth towards the sea surface.
Scientists aboard the March 2002 and March 2003 NOAA research cruises of Kick-‘em-Jenny used SeaBeam technology to measure the depth of the volcano and conduct bathymetric surveys of Kick-’em-Jenny. Bathymetry essentially means “submarine topography”, and a bathymetric survey refers to a series of sophisticated depth soundings over a particular area to determine the depth and shape of the sea floor. Signals are transmitted from the ship down to a specific point beneath the ship and the return speed of these signals is used to calculate the depth. During the recent cruises, scientists sent millions of signals to various points on Kick-’em-Jenny and all of these points, when put together, were used to form a detailed bathymetric map of the volcano. The early surveys over Kick-‘em-Jenny conducted in the 1960s used much less sophisticated technology, and it was only possible to obtain the depth to a few points on the volcano.
During the 1939 eruption, witnesses claimed to have seen an eruption column which was ejected about 900 feet above sea level. The volcano has erupted at least 12 times since then but visible surface phenomena have only been observed twice, in 1974 and 1988. On these occasions material was ejected a short distance into the air and the sea bubbled turbulently above the volcano.
All of the known eruptions of Kick-’em-Jenny since 1939 have been detected by seismographs. Kick-’em-Jenny, like many other submarine volcanoes, is a particularly efficient generator of acoustic signals which are transmitted through the ocean. These can be heard underwater (and on land close to the volcano) as a deep rumbling noise but more importantly they are recorded by seismograph stations, the data from which we are able to read at our headquarters in Trinidad. On several occasions they have been felt strongly in northern Grenada and the Grenadines and perceptibly as far away as Martinique. We refer to these signals as T-phase. Discrete volcanic earthquakes are also sometimes generated, but these are recorded only by seismograph stations very close to the volcano.
Since the current depth to the Kick-’em-Jenny vent (268 m) is considerably lower than the depth at which very explosive eruptions can be expected at this volcano (130 m), we think it is unlikely that an eruption will trigger a tsunami. While it is probable that very large explosions or landslides at Kick-’em-Jenny could generate tsunamis, the threat from tsunamis has been largely over exaggerated. Not all eruptions at Kick-’em-Jenny will generate tsunamis and not all tsunamis will be large. Kick-’em-Jenny has erupted at least 12 times since 1939 and scientists have not been able to confirm that a tsunami was triggered during any of those historic eruptions. Eruption-generated tsunamis may, of course, become a more significant hazard if Kick-‘em-Jenny does begin to grow closer to the surface. Of much more immediate concern at present is the danger posed to shipping due to direct hazards associated with the volcano.
Scientists of the Seismic Research Centre monitor volcanic activity at Kick-‘em=Jenny using a network of instruments installed on nearby islands. The monitoring system includes seismometers (to detect earthquakes), tide gauges (to detect water disturbances), hydrophones (to detect submarine explosions) and tiltmeters and GPS stations (to detect ground deformation). Various combinations of these instruments are installed at Sauteurs, the Sisters rocks, Isle de Ronde, Isle de Caille and Carriacou, and their signals are transmitted to a small base station located at Sauteurs in northern Grenada. From here, the signals are sent to Trinidad. The most important monitoring technique at an active volcano such as Kick-‘em-Jenny is seismic monitoring. Normally, magma (molten rock) is stored in a magma chamber deep beneath the volcano, but if it begins to move towards the surface it will crack rocks as it forces its way up and thus generate earthquakes. Such earthquakes are called “volcanic earthquakes”, and are usually small and shallow, so it is easy to identify them. When many volcanic earthquakes occur beneath a volcano, then scientists know that the volcano might erupt in the near future. This is what happened at Kick-’em-Jenny on Dec 4th 2001. Many small volcanic earthquakes occurred throughout the day, and so the Seismic Research Unit increased the alert level at the volcano. At about 7.15 pm there was indeed a small eruption.
At any given time, the alert level reflects the status of the volcano. Generally, if a volcano is quiet, the alert level for that volcano is GREEN. However, because of a) the ever-present hazard at the Kick-‘em-Jenny in the form of degassing, which could lower the water density above the volcano and cause boats to sink, b) the fact that the volcano erupts so frequently (on average every 5 years) and c) the fact that we cannot physically see the volcano, scientists do not consider the volcano “safe”, which is what would be implied by a GREEN alert level. For this reason, the normal alert level at Kick-’em-Jenny is YELLOW. This alert level requires a 1.5 km radius exclusion zone around the volcano. Should the alert level increase to Orange or Red, as it did during the December 2001 and 2015 eruptions, the radius of the exclusion zone increases to 5 km.
We do not know exactly when Kick-‘em-Jenny will erupt next. We do know, however, that this volcano has erupted 13 times since 1939, on average that is about once every 5 years. Over the last 60 years the longest gap between eruptions has been 12 years, and the most recent eruptions occurred on July 23rd 2015 and April 2017.