The Montserrat Volcano Observatory was established shortly after the first phreatic eruption of the Soufriere Hills Volcano on July 18th 1995. The Observatory is staffed by a variety of scientists supported by local personnel. The main core of the scientific team comes from the Seismic Research Unit of the University of the West Indies in Trinidad. SRU is responsible for all volcanic and earthquake monitoring in the Eastern Caribbean, and 8 staff members of SRU have spent time in Montserrat on rotating tours of duty. The current head of the Observatory is Dr William Ambeh of SRU. Further scientific support has come from the British Geological Survey, the United States Geological Survey, the University of Puerto Rico and several individual researchers from universities in the U.S. and the U.K.
The Observatory is based in temporary accommodation in Olde Towne, northwest of the volcano. This is in the safe zone, so that continuous monitoring can occur even during an evacuation. It is hoped that a permanent observatory will be established sometime in 1996.
The scientists use a variety of instrumental techniques to monitor the volcano.
The signals from 8 seismic stations are transmitted to the Observatory by radio links and phone lines. The stations are located around the volcano and detect the ground movements caused by local earthquakes, phreatic eruptions and flash floods. Occasionally, large earthquakes outside Montserrat are also recorded. The seismic signals are monitored 24 hours a day from the Observatory. Four of the stations are written on paper records to give a real-time view of the seismic activity. In addition, all the signals are digitised and processed on a computer system, which enables the scientists to calculate the location of local earthquakes.
Electronic Distance Meter (EDM) measurements are taken daily. This technique uses an infra-red laser beam to make very accurate measurements between two points. Three reflectors are positioned high on the flanks of the volcano and reflect the infra-red beam back to the instrument which is installed at a fixed point lower down. Daily changes to these measurements are caused by deformation of the volcano, and may indicate the movement of magma. EDM measurements cannot be made when the volcano is cloudy, as the reflectors cannot be sighted.
The Global Positioning System (GPS) is also used to detect deformation. Three GPS receivers record signals from orbiting satellites for a 20-hour period every day. These signals can be processed to calculate the average distance between the receivers, with an accuracy of less than 1 cm. The GPS stations are located further from the volcano than the EDM points, and thus can detect deformation over a wider area; such deformation may be due to a deeper source.
The scientific team makes visual observations from the ground and from helicopter flights over the volcano. Flights to view the crater area are made whenever visibility is good. Occasional trips are made on foot to Chances Peak, on the west side of the crater rim.
Gas samples are collected from the hot springs (soufrieres) and these are analysed for the content of various gases. SO2 monitors have also been placed at various locations around Plymouth to measure the amount of gas that is drifting from the crater area.