Nevis

Geography

Covering an area of approximately 93 square kilometres, Nevis is the smaller of two islands comprising the nation of St. Kitts and Nevis. The two volcanic islands are separated by a 3-km-wide channel called The Narrows. Nevis Peak, the island’s highest point sits in the centre of the island. There are visible wave-breaking reefs along the northern and eastern shorelines. To the south and west, the reefs are located in deeper water. The climate is tropical with little variation, tempered all year round (but particularly from December through February) by the north-easterly trade winds. There is a slightly hotter and somewhat rainier season from May to November. Nevis lies within the track area of tropical storms and occasional hurricanes.

Country Facts

Approximately 11,108 people reside on the island. People are referred to as ‘Nevisian’. The official language is English and ‘Nevisian’ or ‘Nevis Creole’ is also widely spoken. Currency used: Eastern Caribbean Dollar (ECD) and US Dollar.

Disaster Management

In the event of an earthquake, volcanic eruption or tsunami the Nevis Disaster Management Department is the official authority in Nevis.

Nevis Disaster Management Department
Long Point
Nevis, Federation of St. Kitts and Nevis

Tel: +1 869-469-1423
Email: odpnevis@yahoo.com 
Website: https://ndmd.kn/

The Leeward Islands area is the most seismically active zone in the Eastern Caribbean and has hosted the largest magnitude earthquakes to have occurred in the region since the 1600’s, when written accounts for the region began. The average number of background earthquakes, i.e. those that recur on a daily/weekly basis, does not change drastically. The output level sometimes increases in association with the occurrence of a significant magnitude earthquake. This can take the form of foreshocks and aftershocks or only aftershocks. Since 2011, activity in the area has been generally elevated over that seen in previous years. Elevated activity is sometimes precursory to more significant magnitude earthquakes.

The Leeward Islands area, as shown in the epicentral plot, is the most seismically active zone in the Eastern Caribbean and has hosted the largest magnitude earthquakes to have occurred in the region since the 1600’s, when written accounts for the region began. The average number of background earthquakes, i.e. those that recur on a daily/weekly basis, manifest minor fluctuations. The output level sometimes increases in association with the occurrence of a significant magnitude earthquake. This can take the form of foreshocks and aftershocks or only aftershocks. One such period in 2000-2001 exhibited elevated earthquake activity associated with a magnitude 5.6 event on 2000/10/30 that was located east of Barbuda. However, since 2011, activity in the area has been generally elevated over that seen in previous years. Elevated activity is sometimes precursory to more significant magnitude earthquakes. In the epicentral plot shown for the period since 2011, the moderate to strong earthquakes are labelled. Whether or not the elevation being observed is associated with those events or indicative of a more significant magnitude event to come, only time will tell. It may be worthy of note that on 2011/09/06, there was an earthquake of magnitude 5.6 located at 21.66°N and 60.20°W, which is an unusual area for earthquakes to occur and significantly extends the area of increased activity.

During the instrumental era, since 1953, there have been a number of strong to major earthquakes in the area. On 1974/10/08, there was a magnitude 7.4 earthquake located north-east of Antigua/south-west of Barbuda causing damage at Modified Mercalli Intensity VIII in Antigua and lower intensities in the more distant islands. The damage was confined mainly to larger and older buildings, to a petroleum refinery, and to a deep-water harbour. A few people received minor injuries, but no fatality was reported. Then on 1985/03/16, there was a magnitude 6.3 event located west of Antigua/south-east of Nevis that was strongly felt in Montserrat, Nevis, Antigua and St. Kitts.

During the historical era, which dates back to the 16th Century, the first major earthquake in the area, for which there are written accounts, is estimated to have been located close to Nevis and occurred on 1690/04/05. The damage accounts in Robson (1964) suggest impact at Modified Mercalli Intensity IX: In Nevis, landslides occurred on Nevis Peak. The sea withdrew a furlong from Charlestown returning after two minutes. The ground in the lower part of Charlestown was fissured and water discharged.

The region’s great earthquake, at magnitude estimated to be in the range 8.0-8.5, was also located in this area, south-east of Antigua, on 1843/02/08. In this instance also, the maximum intensity, based on damage accounts, has been put at Modified Mercalli Intensity IX. In Charlestown, Nevis, the Court House was destroyed and the Custom House partly destroyed. All masonry houses were severely damaged. Only wooden buildings were habitable. Only two sugar mills in Nevis remained functional. Large landslips occurred on Nevis Peak and a large cloud of dust was raised. Damage in Charlestown was estimated at £50,000. There were no deaths.

The occurrence of such events in the past should be taken as clear evidence of the potential for high level damage from large magnitude earthquakes in the Eastern Caribbean. The absence of such events in the 20th Century should serve to motivate to urgently putting measures in place to mitigate the impact of such events that would in all likelihood occur this century.

Volcanism Overview

The entire island of Nevis is a single volcano with Nevis Peak being the main volcanic centre. Very little is known about the volcanic history of Nevis, though Nevis Peak did erupt significantly in the past to create the large domes present there today. There have been no reports of volcanic eruptions in historical time. However, hot spring activity is significant and there have been five intense earthquake swarms (series of earthquakes) associated with the volcano since the early 19th century. This, along with its youthful appearance, indicates that Nevis is a ‘live’ volcano that will likely erupt in the future.

Future Volcanic Activity

Past activity in Nevis indicates that the most likely style of a future eruption is an effusive dome-forming eruption, similar to the ongoing eruption of the Soufrière Hills Volcano in Montserrat. During an effusive eruption, magma reaches the Earth’s surface and erupts passively or quietly as opposed to an explosive eruption which is more violent. Both types of eruptions are capable of producing deadly volcanic hazards such as pyroclastic flows and surges, as well as associated ash fall and lahars. Should there be an eruption, the Nevis Disaster Management Department is the first point of contact and the entire island of Nevis is likely to be evacuated.

The UWI-SRC scientists provide advice as well as produce maps and other public information material so as to enable the public and authorities to better prepare for volcanic eruptions.

Nevis Peak volcanic centre

• 17.15°N, 62.58°W
• Elevation – 985m
• Last eruption – no records

Nevis Peak volcanic centre, which dominates the island, is the only potentially active centre on Nevis. It is a Peléen-type volcano that has produced andesite to dacite (58 – 65 wt% SiO2; Hutton and Nockolds 1978) lava domes and associated volcaniclastic deposits. The volcanic centre consists of a central or main cone, flank deposits that extend radially to the sea and two younger lava domes. The main cone has a youthful appearance and is almost entirely covered by thick vegetation.

Past eruptive activity

Exposures are largely limited to road cuttings, which predominantly consist of volcaniclastic rocks that are highly weathered and therefore difficult to interpret. The volcaniclastic deposits exposed in the road cuttings are most likely pyroclastic flow, surge and/or lahar deposits. Given the available data, the best interpretation of the Nevis Peak volcanic centre is that it was formed dominantly by effusive eruptions of lava that produced several nested lava domes and voluminous block and ash flow deposits. The largest and oldest of these lava domes forms the bulk of the main cone and has been dated at 0.98 Ma. This lava dome is interpreted to have been built on an older volcanic complex, which is now preserved as a terrace at an elevation of approximately 460 m (Hutton and Nockolds 1978). Periodic collapse of the lava dome generated pyroclastic flows, surges and airfall that blanketed the flanks of the volcano and infilled topography creating the gentle slopes that characterise much of Nevis today.

In an unpublished report, Geothermica Italiana (1991) identified an extensive welded tuff deposit on the northern third of the island. The deposit was dated at 0.23 Ma and interpreted to have been derived from the northern sector of Nevis Peak. Descriptions of this deposit in the Geothermica Italiana (1991) report are limited and no evidence is presented to support the welded nature of the pyroclastic flow deposit. Work by Simpson and Shepherd (2002), Hutton and Nockolds (1978), Hutton (1965) and Martin-Kaye (1959, 1961) does not support the Geothermica Italiana (1991) interpretation of extensive welded tuff deposits on Nevis. Therefore, the Geothermica Italiana (1991) interpretation is currently unsubstantiated and will not be relied upon here.

The northwest quadrant of the Nevis Peak volcanic centre is cut by a 1000 m-wide, semi-circular depression that is open to the west and northwest (see geology map). This was referred to as a breached crater by previous workers (Martin-Kaye 1959; Hutton and Nockolds 1978). The exact origin of this semi-circular depression is unknown, but it was likely formed by the collapse of the northwest summit of the volcano during a dome-collapse event. Geothermica Italiana (1991) suggested that there is evidence for a strongly hydrothermally altered debris avalanche deposit in the Belmont Estate area to the west of Nevis Peak, which may be related to this collapse. Within this depression there is a small dome, which was referred to by Hutton and Nockolds (1978) as the Intracrateral Dome. This dome appears to have grown after formation of the depression as it partially fills the depression. An age of 0.10 Ma has been obtained for this dome (Geothermica Italiana 1991). A second dome called the Great Dome by Hutton and Nockolds (1978) is located on the northern outer slopes of the Nevis Peak volcanic centre. Historical eruptions There have been no reports of volcanic eruptions on Nevis in historic time.

Future eruptions from Nevis Peak & Conclusion

The Nevis Peak volcanic centre is likely to erupt again in the future. Past activity in Nevis indicates that the most likely style of a future eruption is an effusive dome-forming eruption, similar to the ongoing eruption of the Soufrière Hills volcano in Montserrat. Less likely is an explosive magmatic eruption.

Future hazards are expected to include volcanic earthquakes, pyroclastic flows, pyroclastic surges, airfall and lahars. Evidence for past explosive eruptions has not been documented; however this style of eruption cannot be ruled out. The most recent eruptions from the Nevis Peak volcanic centre have come from the summit area of the main cone, and this is regarded as the most likely vent area for a future eruption.

The integrated volcanic hazard maps developed by the UWI-SRC should be used by emergency management officials to draft contingency plans. The continuous operation of a volcano monitoring network is an essential component in predicting and mitigating the effects of future eruptive activity.

Related Resources

Volcanic Hazard Atlas of the Lesser Antilles

Two localities on Nevis, Cades Bay Soufrière and Farm Estate Soufrière, are sites of minor fumarolic activity. A number of hot springs are also present; the hottest are those at the Bath Estate and at Cades Bay beach. In addition there are large areas of pervasively hydrothermally altered rock present throughout the island (e.g. Clarks Ghut) that are interpreted as areas of past/extinct fumarolic activity. Current geothermal activity is largely concentrated on the western half of the island.

Cades Bay Soufrière

The Cades Bay Soufrière is an area of warm, hydrothermally altered ground ~ 30 x 30 m in size. Local residents and Robson and Willmore (1955) report that the Cades Bay Soufrière began to form in 1953 with the burning of vegetation, deposition of sulphur in the soil, and development of small boiling pools and vigorously steaming vents. Soil temperatures of up to 100C were reported for these early stages (Robson and Willmore 1955). In more recent years activity has decreased considerably, with steaming vents only visible during and after heavy rainfall. In 2001 ground temperatures of 100o C were measured. It is likely that the Cades Bay Soufrière formed in response to local readjustments in the groundwater system brought about by the severe earthquake swarm in Nevis between 1950 and 1951.

Farm Estate Soufrière

The Farm Estate Soufrière is an area of warm, hydrothermally altered ground occupying part of the Sulphur Ghut stream valley and from which sulphur has been mined in the past for gun powder. A few weakly steaming vents are present, with more energetic steaming vents appearing after heavy rainfall. The activity at Farm Estate appears to have been at this low level for at least the last 60 years. Robson and Willmore (1955) report that the Farm Soufrière ‘was found to be nearly extinct’ when they visited it in 1953, although they obtained temperatures from within small crevices of up to 100o C. More recently (2001) temperatures of up to 99.3o C were obtained from weakly steaming vents.

In 2008, West Indies Power Company drilled three small diameter exploratory wells about 3.7 km apart, to depths ranging from 782 to 1,134 meters in the Spring Hill, Jessups, and Hamilton Estates areas. All three wells encountered temperatures in excess of 225 oC and significant steam was produced. Geothermometric projections suggest reservoir temperatures of at least 260 oC (LaFleur and Hoag, 2010). In November 2013, Nevis Renewable Energy International was selected by the Nevis Island Administration to replace West Indies Power as the resource developer. This firm plans to build a 5-10 MW power plant to generate electricity for domestic use and, if possible, to export power to nearby St. Kitts. At this time, West Indies Power Company is challenging the right of the government to reassign the project (extracted from Huttrer and LaFleur, 2015).