It has come to our attention that residents in some parts of Dominica have recently been noticing an unusually strong smell of sulphur, particularly in the areas of Laudat and Morne Prosper. We have also been informed that the Boiling Lake is emitting unusually strong smells and is currently a murky black colour.

The reasons for these changes in activity are unclear at the present time. However, it is possible that they are related to the unusually hot and dry season that we are currently experiencing in the Caribbean. We believe that these sulphurous smells are NOT related in any way to the swarm of shallow earthquakes that has been occurring over the past two days in the north of Dominica. We are at present investigating the possibility that the black colour of the Boiling Lake reflects the presence of colloidal sulphur.

The Boiling Lake has been known to undergo changes in the past, and its water level has even dropped drastically on occasion. These past incidents appear to have reflected local changes in the geothermal system, and were not related to an increase in volcanic activity. However, in 1901 a small steam and gas explosion from the Boiling Lake (which was almost empty at the time) released harmful gases (probably mainly carbon dioxide) into the atmosphere and killed two people who were at the water’s edge at the time. This incident highlights the potential dangers of the Boiling Lake, especially at times of unusual activity. For this reason, we recommend that people exercise extreme caution when visiting the Lake in its current state. We recommend that:

1) no one climbs down to the water’s edge at this time, and

2) visitors to the Valley of Desolation either avoid approaching the Lake or make their stay at the viewing point above the Lake as short as possible.

Within the next few weeks staff from the Seismic Research Unit will be making a routine visit to Dominica to carry out regular monitoring of the geothermal areas (soufrière). At that time we will be able to release more information about the phenomena discussed here. In the meantime, if anyone notices any further changes in Dominica’s geothermal areas, they should contact the Seismic Research Unit (uwiseismic@uwiseismic.com).

We have been notified that guides and visitors to the Boiling Lake in Dominica have recently reported an unusually strong smell of sulphur coming from the Lake, which is currently a murky black color. The Boiling Lake has been known to undergo changes in the past, and its water level has even dropped drastically on occasion. These past incidents appear to have reflected local changes in the geothermal system, and were not related to an increase in volcanic activity. The current changes in activity may be associated with the unusually hot and dry season that we are currently experiencing in the Caribbean. Possible causes for the changes in the lake are outlined below:

The water level in the lake has dropped with or without an increase in gas emissions at the bottom of the lake. This could result in either or both of the following: The churning up of the lake bottom sediments by the gases being emitted at the lake bottom. Hence the murky black color of the lake and the sulphur smells. An increase in lake water temperature resulting in increased activity of sulphur oxidizing bacteria inhabiting the lake. Such bacteria are responsible for producing larger amounts of iron monosulphide (FeS), a black particular solid that would make the color of the lake appear black. This is common in many geothermal areas, including the Valley of Desolation (see photo). There is an increase in dissolved metal ions (e.g. Fe3+, Fe2+) in the lake water due to increased gas emissions at the bottom of the lake. This has resulted in an increased production of iron monosulphide (FeS) in the lake. Landslide material being washed into the lake has led to some changes in its appearance. It is believed that the changes in the lake appearance and smell may actually be due to a combination of the scenarios described above. We believe that these changes are NOT related in any way to the swarm of shallow earthquakes that has been occurring over the past several days in the north of Dominica.

Within the next few weeks staff from the Seismic Research Unit will be making a routine visit to Dominica to carry out regular monitoring of the geothermal areas (soufrière). At that time we will be able to release more information about the phenomena discussed here. In the meantime, if anyone notices any further changes in Dominica’s geothermal areas, they should contact the Seismic Research Unit (uwiseismic@uwiseismic.com).

Black waters in the Valley of Desolation on the trail leading to the Boiling Lake. Such black waters are caused by the presence of iron monosulphide (FeS) and are common in many geothermal areas. (Photos courtesy Challie Minton, Dominica)

Since the last report was issued on April 22 there have been two new developments. We have installed an extra seismograph station at Hillcrest Estate House in northern Dominica (DHCT on the map below). This station is in the middle of the source zone of the current activity and will improve the quality of earthquake locations considerably. There are now four state-of-the-art seismograph stations in northern Dominica at the locations shown in the next diagram as solid stars.

Map showing locations of earthquakes (open stars) and seismograph stations (solid stars) in northern Dominica. There are eight more stations off the map to the south.

The closed lines show the summit regions of the two live volcanoes of northern Dominica at the 800 meter contour. A few earthquakes are now happening directly beneath Morne aux Diables but the much larger Morne Diablotins is still seismically inactive. The overall pattern of activity continues to suggest that this earthquake activity is not related to volcanic activity and the alert level at both volcanoes remains GREEN.

In the week of May 23-30 scientists from the Seismic Research Unit visited Dominica to take samples from the hot springs in all parts of the island. One particular result is that the team confirmed the changes in the appearance of the Boiling Lake which has turned almost entirely black. The cause of this is a combination of increased gas emission into the lake and an unusually dry and prolonged dry season which has lowered the level of the lake. This is largely a meteorological phenomenon and is unconnected with the seismic activity further north. Further results will be released when laboratory analyses have been completed and a further visit will be made later this month when UWI scientists will be joined by a team from the University of New Mexico.

9:00AM Wednesday 31 December 2003

Investigations instigated by the Lieutenant-Governor of Saba Mr. Antoine Solagnier have identified the source of the seismic events recorded over the past ten days. The main pier of the harbour in Saba was damaged by hurricane Lenny in 1999 and is now being demolished in preparation for replacement. It is being demolished by a crane which hoists a ten-tonne mass to a height of approximately 25 meters and then drops the weight onto the pier. The demolition site is about one kilometer horizontally and 320 meter vertically from our seismograph station and the energy generated bythe impcts is entirely sufficient to explain the observed signals.

Update 5 PM Tuesday 30 December 2003

The seismic events in Saba have continued at a rate of about one every five minutes throughout the afternoon. The events are spaced extremely regularly, and occur only during daylight hours which suggests an artificial origin but investigations in Saba have not yet identified a possible cause.

Update 12 Noon Tuesday December 30

The sequence of seismic events in the island of Saba which began last week and continued to December 28 was renewed briefly today, December 30, when seven (7) events occurred in rapid succession between 10:43 AM and 11:00 AM Local Time. Saba is the smallest island under separate administration in the eastern Caribbean and essentially consists of the single volcano Mt. Scenery. Pictures and descriptions of Mt. Scenery can be found on the Documents section of this site.

The most recent severe earthquake swarm near Saba occurred in 1992 (Ambeh and Lynch, Tectonophysics 246 (1995) 225-243. These authors considered that the 1992 events had a tectonic rather than volcanic origin. The ongoing events are much smaller than those of 1992 and the most likely explanation at the moment is that they are of artificial origin.

No descriptions of volcanic eruptions in Saba have been found in the literature written since Europeans first began to settle there in 1640 AD. This is slightly puzzling because the youngest pyroclastic flow deposits in the island contain fragments of European pottery, and a radiocarbon date for these deposits suggests that they were erupted in 1670 AD (+/- 60 years). Other radiocarbon dates for different deposits are 1425 AD (+/- 60 years), 3,155 +/- 65 years and 34,750 (+/-850 ) before present. The more recent eruptions occurred while the island was occupied by Amerindians and the most recent may have been since European settlement. Further literature searches may yet yield descriptions of this event (or events).

28 December 2003

Over the Christmas period and continuing to Sunday December 28 our seismograph station in Saba recorded a very large number of small seismic events. At the moment we are uncertain whether these are genuine earthquakes or whether the signals are generated by some other activity such as onshore or offshore explosions. All that we know is that the signals are being generated on or close to the island of Saba, in the Netherlands Antilles. If anyone can cast any light on these phenomena please e-mail us at uwiseismic@uwiseismic.com.

Chan Ramsingh (IT Officer) and Ian Juman (Electronics Technician) of the Seismic Research Unit, established a new seismograph station in St. Martin on March 8th. The new station is a 3-component digital broadband station with GPS satellite timing and an internet link to Unit headquarters in Trinidad. The station is located in the meteorological office at the airport by kind permission of the director of the meteorological service, Mr Ashford James. The stations in Saba and Statia were also upgraded.

The UWI network in the northwestern Lesser Antilles now includes 10 stations distributed as shown in the diagram below.

The Seismic Research Unit has been notified by Forestry Officers of the Forestry & Wildlife Division of Dominica that the water level and geothermal activity of the Boiling Lake, Dominica have significantly decreased. On December 28th a team of Officers were sent to investigate the situation and were able to verify that the water levels in the Lake had dropped by approximately 30 – 40ft. In addition there was no vigorous boiling or steaming, and the lake’s temperature was much lower than as is usually observed. The Boiling Lake has been known to undergo changes in the past, and a reduction in water level has been observed on four previous occasions: April-May 1988, April 1971, January 1901, and December 1900. The historical record as well as the present day volcano monitoring network indicate that these past incidents reflected local changes in the geothermal system, and were not related to any changes in the level of volcanic activity. Similarly the recent changes in activity may have resulted from changes in permeability of the rock materials beneath the Boiling Lake along with blockage of fumarolic vents in the crater. An increase in permeability of the subsurface layers would enable the crater waters to drain away faster than they are being replenished by the two surface streams. Blockage of the fumarolic vents would lead to a reduction in steam emission and hence in the temperature of the crater water. Given the recurrent nature of the recent changes at the Boiling Lake, scientists at the Seismic Research Unit will undertake an investigation so as to better understand the causes.

Despite the fact that it is unrelated to any increase in volcanic activity the recent changes at the Boiling Lake does increase the potential hazards to visitors to the area. In 1901 a small steam and gas explosion from the Boiling Lake (which was almost empty at the time) released harmful gases (probably mainly carbon dioxide) into the atmosphere and killed two people who were at the water’s edge at the time. This event highlights one of the main potential dangers of the Boiling Lake, especially at times of unusual activity. For this reason, we recommend that people exercise extreme caution when visiting the Lake in its current state. Specifically we recommend that:

1) No one climbs down to the water’s edge at this time, and

2) Visitors to the Valley of Desolation either avoid approaching the Lake and/or spend as little time as possible at the viewing point on the crater rim.

Boiling Lake, Dominica, with decreased water levels.

In the meantime, if anyone notices any further changes in Dominica’s geothermal areas, they should contact the Seismic Research Unit at uwiseismic@uwiseismic.com.

St. Augustine, Trinidad and Tobago, W.I. –January 5th, 2005 – The recent tsunami in Asia has caused widespread concern over the Caribbean’s vulnerability to tsunamis. While it is possible for the region to be hit by a tsunami such as the one recently experienced in Asia, scientists currently believe that there is a very low probability of this phenomenon occurring in the Caribbean. Additionally, questions have been raised as to the threat of a tsunami from an eruption of Kick ‘em Jenny. Currently, the threat of a tsunami from an eruption of the volcano is extremely low since a recent (2003) survey revealed that the summit of the volcano is quite deep. There has been no unusual activity at the volcano and the alert level remains at yellow, which is normal for Kick ‘em Jenny. At the moment, Kick ‘em Jenny poses a grave danger to shipping as the volcano is constantly emitting gases, which lower the buoyancy of the water and can cause vessels to sink. For this reason there is a 1.5km exclusion zone around the summit of the volcano.

A tsunami is an ocean wave or series of waves caused by a large-scale disturbance of the ocean floor or surface that abruptly displaces a large mass of water. Tsunamis may be caused by earthquakes, volcanic events, landslides into the sea or impact of stellar objects such as asteroids, comets and meteorites. This article focuses primarily on tsunamis generated by earthquakes and volcanic events.

In the past 500 years there have been at least ten earthquake-generated tsunamis in the entire Caribbean which have been reported and verified. Four of these have led to deaths. In total about 350 people in the Caribbean have been killed by these events. These tsunamis occurred as a result of earthquakes in:

Additional earthquake-generated tsunamis of note also occurred in 1843 affecting Guadeloupe and Antigua and in 1690 in St. Kitts Nevis. The number of casualties related to these tsunamis, if any, is uncertain. In July 2003, a major dome collapse from the Soufriere Hills Volcano in Montserrat caused a tsunami that was experienced in Guadeloupe at about 1m high and in some parts of Montserrat at 4m in amplitude.

Potentially, there are two groups of earthquakes which may generate tsunamis in the Caribbean. These are (1) Earthquakes occurring within the region which may generate local tsunamis (by local we mean that only nearby islands are affected). In the past 500 years there have been approximately 50 potentially tsunamigenic local earthquakes but only 10-20% of these earthquakes actually generated tsunamis that caused significant inundation. (2) Distant earthquakes occurring outside of the region may generate tele-tsunamis.

In November 1755, a major earthquake in the Azores fracture zone near Portugal resulted in a tele-tsunami which crossed the Atlantic and was noticed throughout the eastern Caribbean from Barbados to Antigua and as far west as Cuba. This earthquake is commonly referred to as the Great Lisbon Earthquake. The amplitude of the tsunami in all islands was about 2-3 metres and waves continued to arrive for many hours. No damage or casualties were reported. European sources also reported that the Azores fracture zone generated a second tele-tsunami in March 1761 but no local confirmed observations were made in the Caribbean.

While recent events in Asia have caused much concern over the Caribbean’s vulnerability to tsunamis, it is important to note that all oceans can experience tsunamis but there are more large, destructive tsunamis in the Pacific Ocean because of the many major earthquakes along the margins of the Pacific Ocean and also because dip-slip earthquakes (which involve vertical rather than lateral ground motion) are more common in the Pacific than elsewhere. As a result of the immediacy of the tsunami hazard to countries in the Pacific, there is currently a tsunami early warning system in that region.

There is no tsunami warning system in the Caribbean where the recurrence rate is approximately: 1 destructive tsunami per century for local earthquakes and 1 destructive tsunami per 200 years for distant earthquakes. It should be noted that these recurrence rates are small but not negligible. For comparison, earthquake engineers design buildings to withstand earthquakes with a recurrence period of once in 475 years.

The first sign of an approaching tsunami is usually a significant retreat of the sea. As a result, the trailing waves pile on top of the waves in front of them, thereby significantly increasing the height of the wave before hitting the shore. Although a tsunami advances much slower as it approaches land, its momentum is powerful enough to cause severe destruction. If you are close to the sea and the water retreats by an abnormal amount, move to high ground at once. While it is possible that the region could be affected by earthquake-generated tsunamis, scientists currently believe that the more immediate threats posed by earthquake hazards such as collapsing buildings, falling electricity lines, ruptured gas lines, rock slides and/or landslides on mountains and hillsides (as recently witnessed in Dominica, Trinidad, the British Virgin Islands and the Cayman Islands) are more of a present danger to the region. Greater focus should, therefore, be placed on ensuring that effective public education programmes are undertaken to sensitize the public to these hazards and serious consideration should be given to constructing sound earthquake-resistant buildings.

For updates on these and other geologic events occurring in the region please visit the Seismic Research Unit’s website at www.uwiseismic.com. Based at the University of the West Indies in St. Augustine Trinidad, the Seismic Research Unit is the agency responsible for monitoring earthquakes and volcanoes throughout the English-speaking Eastern Caribbean.

St. Augustine, Trinidad and Tobago, W.I. –January 7th, 2005 – The recent tsunami in Asia has caused widespread concern over the Caribbean’s vulnerability to tsunamis. While it is possible for the region to be hit by a tsunami such as the one recently experienced in Asia, scientists currently believe that there is a very low probability of this phenomenon occurring in the Caribbean. Additionally, questions have been raised as to the threat of a tsunami from an eruption of the Kick ‘em Jenny submarine volcano which is located north of Grenada.

Currently, the threat of a tsunami from an eruption of the volcano is extremely low since a recent (2003) survey revealed that the summit of the volcano is quite deep. There has been no unusual activity at the volcano and the alert level remains at yellow, which is normal for Kick ‘em Jenny. At the moment, Kick ‘em Jenny poses a grave danger to shipping as the volcano is constantly emitting gases, which reduces the water density and can cause vessels to sink. For this reason there is a 1.5km exclusion zone around the summit of the volcano.

For updates on these and other geologic events occurring in the region please visit the Seismic Research Unit’s website at www.uwiseismic.com. Based at the University of the West Indies in St. Augustine Trinidad, the Seismic Research Unit is the agency responsible for monitoring earthquakes and volcanoes throughout the English-speaking Eastern Caribbean as well as the Dutch islands of Saba, St. Eustatius and St. Martin.

The Seismic Research Unit has been notified by Forestry Officers of the Forestry & Wildlife Division of Dominica that the water level and geothermal activity of the Boiling Lake, Dominica have been gradually returning to its normal status. Field visits by Forestry Officers on Tuesday 18th January, as well

as reports from other visitors to the Lake, have confirmed that the water levels in the Lake is now ~20ft below the high water mark. In addition, there has been an increase in the degassing of the submerged fumaroles within the Lake, which can now be observed as bubbling of the water at the Lake’s surface. These changes in the activity of the Boiling Lake are again believed to be a reflection of local changes in the geothermal system, and are not related to any changes in the level of volcanic activity.

We still wish to emphasize that people exercise extreme caution when visiting the Lake in its current state. Specifically we recommend that:

1) No one climbs down to the water’s edge at this time, and

2) Visitors to the Valley of Desolation either avoid approaching the Lake and/or spend as little time as possible at the viewing point on the crater rim.

In the meantime, if anyone notices any further changes in Dominica’s geothermal areas, they should contact the Seismic Research Unit (uwiseismic@uwiseismic.com).

Boiling Lake, Dominica, with increased water levels.

St. Augustine, Trinidad W.I.– March 23rd, 2005 – In commemoration of the 10th anniversary of the eruption of the Soufrière Hills Volcano on Montserrat, the Seismic Research Unit of the University of the West Indies is spearheading a conference entitled ‘Soufrière Hills Volcano – Ten Years On’. Organised in collaboration with the Montserrat Volcano Observatory, the conference will attract scientists, emergency management personnel, health officials, and educators from across the globe.

The eruption on Montserrat has become a significant volcanic event both because it has attracted intensive scientific study and because of its long-lasting effects on a small island nation. It has so far produced over 0.5 km3 of andesite magma and has displayed a remarkable range of volcanic phenomena, including pyroclastic flows and tsunamis. It has also had a severe social impact, rendering two-thirds of the island uninhabitable and resulting in the emigration of more than half the island’s population.

With the installation of state-of-the-art monitoring equipment the eruption has been documented in unprecedented detail. As a consequence the volcano has become a natural laboratory for the science of volcanology and continues to stimulate a great deal of research in all spheres of volcanology and volcano seismology ranging from issues concerned with magma generation to the development of tools to improve the interface between science and society.

The Eastern Caribbean is a region of active volcanism that contains 19 ‘live’ (likely to erupt again) volcanoes and has experienced 33 historical eruptions (i.e. since the 1700s). Every island from Grenada to Saba is subject to the direct threat of volcanic eruptions. Non-volcanic islands such as Antigua, Barbados, Trinidad and Tobago are close to volcanic islands and are, therefore, subject to volcanic hazards such as severe ash fall and volcanically-generated tsunamis.

The conference will be restricted to about 150 participants and will be held on the island from the 24th-30th July, 2005. Further details can be found at www.uwiseismic.com and at www.mvo.ms.