255070
_{(was 0505-07)}
Water and Mineral Resources Division
Ministry of Energy, Water and Minerals Resources
P.O. Box G37
Honiara
Solomon Islands

Staff :

Donn H. Tolia - Director of Geology
Thomas Toba - Seismology

Most interest in terms of volcanic hazards are situated within the volcanic province itself.

Most of the volcanic activity is of Plio-pleistocene age and still remnants of activity is that of Tinakula, Savo, Simbo, Kavachi and the numerous number of submarine volcanoes, such as the Coleman mount, Kanakeoki, and Cook sub-volcano.

VOLCANOES OF THE SOLOMON ISLANDS

1. Tinakula

Tinakula is situated in the Santa Cruz group of islands in the eastern Solomons at latitude 10.3° South and longitude 165.3 East. It was reported by Hughs in 1975 to be active in 1595 as observed by the Spanish explorer Alvaro de Mendana. The last reported large eruption was in 1985. Tinakula is highly active which erupts andesitic ash almost every week.

2. Savo

Savo Island is situated some 35 km Northwest of Honiara Solomon Islands Capital and urban centre. Savo island is the surface expression of a stratovolcano ; only the top one third of the structure is visible above sea level. Savo has been dormant for around 100 years. There are historical records which describe two eruptions from Savo ; one description is from 1568 when the Spanish explorer Alvaro de Mendana visited Solomon islands, and a second report describes a ten year eruption phase during the 1830's and 1840's with continued steam related activities until 1880's. One recently determined radiocarbon age date indicates volcanic activity occurred between 1600 and 1700.

Recent studies of the oral history traditions of Savo have shown that two other eruptions are recorded one of which appears to have been extremely destructive. The oral history also records a particular destructive mudflow. Thus available evidence suggests that Savo is periodically active with inactive repose periods of between about 100 and ?300 years. Further studies are required to gain a greater understanding of the frequency of eruption.

3. Kavachi

A submarine volcano situated approximately 25 km south of Vangunu Island in the Western Solomon having latitude and longitude of 9.37 S and 157.93 E respectively. According to records Kavachi has erupted 6 times in the last 30 years. (Johnston and Tuni, 1987). Kavachi forms a temporary island during its eruptive phases which occur every 4-8 years.

4. Simbo

This volcano has no records of eruptions in historical times. This is the second highest volcano which pose some risk to the population apart from Savo. In one instance, a minor emergency occurred as a result of increased steam emission and sulphur fire (possibly man made) within the crater in February 1993. This has caused a great concern among the population. Because of the number of inhabitants a population of @ 2000-3000, this too deserves to be investigated, to establish the size or magnitude and the frequency of its prehistorical eruptions.... The traditional oral history should be investigated for possible historical volcanic eruptions. This volcano is currently in a fumarolic-solfataric phase of activity.

VOLCANIC HAZARD

Monitoring and Surveillance

The Solomon Islands Geological Survey is part of the World Wide Standard Seismological Network (WWSSN) headed by the USGS. Currently, at the headquarters in Honiara an Iris Digital system is being set up to monitor the tectonic activities of the region which is more concentrated on seismic activities. The Department has problems in setting up a good net work to monitor volcanoes of the Solomons due to financial and technical aspects. Because of these, the Geology Division of the Solomon islands is concentrated on one particular island due to its geographical position to the main urban and development centres and that is Savo Island.

At the present time the WMRD have one 3 component seismometer installed on Savo, (telemetered) which is provided in conjunction with an Israel Microseismic zoning project set up late last year, 1996. There is one direct radio link between one village on Savo and the WMRD. The Savo seismometer is only intermittently operational which is another problem with regards to the present level of volcanic monitoring by the WMRD. The only other monitoring exercise undertaken by the WMRD at the present time is the collection of fumarole temperatures at regular intervals.