The University of the West Indies Seismic Research Centre

Eruptive History
Written histories of the West Indies do not mention the Kick 'em Jenny volcano before 1939, although there must certainly have been many eruptions before then. The name "Kick 'em Jenny" appears on many old maps where it usually refers either to the small island now more commonly called Diamond Rock (or Île Diamante) or to the whole passage between the Île de Ronde and Grenada.

23rd-24th July, 1939
The presence of the volcano was first revealed by an eruption which occurred on July 23rd-24th, 1939. It was witnessed by a large number of people in northern Grenada including a well-known Grenadian historian, Fr. R.P. Devas, who wrote a two-page typescript account of the eruption, a copy of which is at the Seismic Research Unit.

This eruption lasted for at least 24 hours and at its height it ejected an eruption column 300 metres (900 feet) above sea level. The eruption generated a series of sea waves which had amplitudes of about 2 meters in northern Grenada and the southern Grenadines.

Since 1939 there have been at least twelve more eruptions of Kick 'em Jenny. None of these have been as big as the 1939 eruption and most have been detectable only by seismographs. The most recent eruption of the volcano occurred in December 2001.

The 1939 eruption of Kick `Em Jenny probably looked similar to this eruption of the Kavachi Submarine Volcano in the Solomon Islands. (Photo by Pamela Brodi, 2000)

4th-6th December, 2001
Elevated activity at Kick 'em Jenny occurred between December 4th and 6th, 2001. It was the first active episode to be preceded and accompanied by genuine volcanic earthquakes since seismograph networks were established in the Eastern Caribbean in 1952. The first signs of the underwater volcano's unrest were observed on September 24th, 2001 with a premonitory earthquake directly beneath the volcano. On December 4th, scientists at the Seismic Research Unit observed a burst of seismic activity beginning at 6:00AM (local time) and increasing to a peak at about 11:00AM. Following a short lull, activity again increased, and culminated in bursts of "T-phase*" between 7:18PM and 10:31PM. These bursts of T-phase were interpreted as explosions associated with a submarine eruption. After this burst of activity things quieted down, and earthquake activity returned to background levels.

The December 4th eruption appeared to have been completely submarine, with no observed or reported activity at the surface (although it did occur at night, so we cannot say for sure that there were no surface manifestations). Despite the lack of subaerial activity, the presence of T-phase confirmed that Kick 'em Jenny had erupted. The largest earthquakes associated with the eruption were felt in northern Grenada.

* T-phase, also known as "T-wave" is an acoustic wave from an earthquake or underwater explosion (e.g. submarine volcanic eruption). When an earthquake occurs in the earth's crust under the ocean or a submarine volcano erupts, in addition to the usual earthquake waves - i.e. "P" (primary) and "S" (secondary) waves - a third wave (T-wave) is generated by the acoustic energy in the ocean. The "T" stands for "tertiary", because these waves travel the slowest and so arrive after both the P and S waves at seismic stations.

Hourly (red bar chart) and cumulative (continuous line) numbers of volcanic earthquakes recorded at GRW from 6:30 AM, Dec. 4 to 6:30 AM, Dec. 6, 2001. Vertical arrows are T-phase episodes.

23rd-24th July 2015

On 23rd July, 2015 at 01:42 a.m. (local time) a strong, continuous signal was recorded on the GCMP and GRGR seismic stations, which are located at Mt. Pleasant, Carriacou and Meribu, Grenada respectively, that lasted until about 02:58 a.m. local time. Based on the strong T-phase signals that were recorded at seismic stations in Montserrat, the signal was interpreted to be an eruption from the Kick-‘em-Jenny volcano. A second eruption, which lasted about an hour, was recorded the following morning, 24th July, from 00:02 a.m. These eruptions were the
culmination of volcanic unrest at the volcano that began on 11thJuly 2015 with two earthquakes of volcanic origin and steadily increased. Following the eruptions, volcanic seismicity rapidly subsided to background.

29th April 2017
The eruptive activity on 2017/04/29 is among the shortest ever recorded at the KeJ; it consisted of one eruption, which lasted just 14-minutes, followed by tremor lasting about an hour. The period of unrest began on 8th April with one KeJ earthquake.On the days following that first event and prior to the eruption the daily number of earthquakes was in the range 0-2, with 16 in all leading up to the eruption. After the eruption, there was a sharp increase in the output rate, with an additional 84 events up to the 2nd May, after which the earthquake activity ceased. The eruption was felt in northern Grenada and Martinique as an extended period of shaking. There was no surface evidence of the occurrence of the eruption.

The 2015 eruption episode was similar to that of 2001 only in the high level of precursory earthquakes and rapid decay of post-eruption seismicity. There were, however, only two eruptions, separated by approximately 24-hours, both lasting about an hour. The 2017 eruption episode was unique; the precursory seismicity was low level; the eruption occurred without intensification of precursory seismicity and the post-eruption seismicity was relatively abundant, but short-lived. The type of earthquakes seen following the 2017 eruption was different from those in 2001, 2015 and the precursory earthquakes in 2017. This difference along with the low level of precursory 2017 events may signal changes in the KeJ conduit and crater that may influence the activity seen in the next eruption episode; a pattern similar to that prior to 2001.

Historical Activity at Kick 'em Jenny 1939-Present

Date	Description	Evidence for eruption
24 July 1939	Eruption cloud up to 270m above sea level: local felt earthquakes; large sea waves generated (1m in open water); largest known historical eruption	Witnessed
5 Oct. 1943	Submarine eruption; local felt earthquakes.	T-phase recorded in Martinique.
30 Oct. 1953	Submarine eruption; earthquakes felt in north Grenada	T-phase recorded throughout Eastern Caribbean.
24 Oct. 1965	Submarine eruption; earthquakes of intensity V felt on Isle de Ronde	T-phase recorded throughout the Eastern Caribbean (and traced to KeJ)
5-7 May 1966	Submarine eruptions; earthquakes in north Grenada	T-phase recorded throughout the Eastern Caribbean (and traced to KeJ)
3-6 Aug. 1966	Submarine eruption, 168 free T-phase recorded, shocks with intensities less than or equal to IV felt in Grenada	T-phase
5 July 1972	Submarine eruption about 5 hours long	T-phase recorded throughout the Eastern Caribbean
6 Sept. 1974	Material ejected into the air; sea above the volcano bubbling turbulently and spouting steam	Witnessed; T-phase recorded throughout the Eastern Caribbean
14 Jan. 1977	Submarine eruption.	T-phase recorded throughout the Eastern Caribbean
29-30 Dec. 1988	Submarine eruption; turbulent discoloured water; earthquakes felt in north Grenada	T-phase
26 March to 5 April 1990	Earthquakes felt in north Grenada	T-phase recorded throughout Eastern Caribbean
4 Dec. 2001	Submarine eruption, earthquakes felt in north Grenada	T-phase recorded throughout Eastern Caribbean (and traced to KeJ). More than 600 volcanic earthquakes recorded on proximal stations.
23-24 July 2015	Submarine eruption; earthquakes felt in Grenada	T-phase recorded in Montserrat
29 April 2017	Submarine eruption; earthquakes felt in Grenada and Martinique	T-phase recorded in Montserrat