Seismicity around Kick-’em-Jenny maintains a continuous background level. In times of unrest, increased seismicity is the key factor scientists use to ascertain when the volcano might erupt in the near future. 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.
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 SRC has established a monitoring network and warning system specifically for Kick-’em-Jenny. The main purpose of this is to provide warning to shipping in the vicinity, it is not a tsunami warning system. Since tsunamis travel very rapidly, by the time one has been generated it is already too late to issue a warning. Furthermore, tsunamis are only generated by big eruptions, and such eruptions take time to build up. The monitoring system is therefore designed to detect premonitory symptoms before the eruption begins, and to allow scientists to judge whether an eruption is building up to a stage where a tsunami could be generated. In this way vulnerable communities will be given warning prior to a large eruption, enabling them to evacuate to higher ground.
Recent upgrades in the monitoring system have resulted in a strong network of monitoring equipment surrounding the volcano as well as the development of a small, dedicated volcano observatory on nearby Grenada. This upgrade was made possible through a grant from the Caribbean Development Bank. The monitoring system includes a network of 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 (see figure below).
Alert Level System
At any given time, the alert level reflects the status of the volcano. The alert levels for volcanoes in the English-speaking Caribbean are set by a committee which consists of the professional scientific staff of the Seismic Research Centre although we often consult with other scientists with special knowledge of this region. Governments with responsibility for the volcano in question are consulted before the alert level is changed but this may not always be possible as alert levels may change very rapidly. For example the Soufriere volcano of St Vincent went from mild premonitory activity to full-scale eruption in less than 18 hours in 1979.
The table below outlines the alert levels for Kick-’em-Jenny ONLY. Alert levels for volcanoes on land are defined slightly differently. Kick-’em-Jenny is neither visible nor audible until it is in full eruption so that one of the most useful volcanic monitoring techniques – visible inspection – is not possible. Kick-’em-Jenny has been in a state of continuous low-level activity since 1939 at least and it can be dangerous to spend time directly over the volcano. Since scientists can neither see nor hear the volcano, the lowest alert level for Kick-‘em-Jenny is YELLOW and the exclusion zone around the volcano’s summit should be observed by maritime vessels at all times. See NADMA for more information.