WOVO.org

World Organization of Volcanic Observatories

1803
Volcanological Station of the Canary Islands
Spanish Research Council
P.O. Box 195
38206 La Laguna
Tenerife, Canary Islands
Spain

Note: Tenerife, La Palma and Lanzarote are the most volcanically active islands of the Canarian Archipelago, with 16 "historical" eruptions since the 15th century, the last occuring in 1971. This basaltic fissural volcanism is closely related to active rift-type volcanic structures (Carracedo and Rodríguez Badiola, 1991; Carracedo et al., 1992). In Tenerife, one of the most densely populated islands (over 600.000 inhabitants and more than two million visitors per year), a central silicic volcanic complex (Teide-Pico Viejo) is also present, the last eruptive episode of which took place in the 15th century.

A joint program of the Canarian Government (the Department of the Environment) and the Spanish Research Council (the Volcanological Station of the Canary Islands) resulted in an important improvement in the instrumental facilities for the research and monitoring of this active volcanism.

The Volcanological Station (Spanish Research Council) and the Department of Geology (University of La Laguna, Tenerife) reached an agreement to combine human and technical resources for the study and monitoring of volcanic activity. This agreement implies working as a team in the event of an eruptive crisis in the Archipelago.

Scientist in charge: Juan Carlos Carracedo.

Staff:

Juan Carlos Carracedo - Geology, Volcanology
Julio Alberto Castro A.- Physics
Vicente Soler - Geophysics
Juan Manuel Cabrera Perarza - Lab Assistant
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Mariano García - Geophysics, Seismology
Nemesio Pérez - Geochemistry
Maria José Jiménez - Geophysics, Seismology
Eduardo R. Badiola - Geology, Geochemistry
Juan Coello - Geology, Petrology
Julio de la Nuez - Geology, Petrology
Carmen Rosa Cubas - Geology, Geochemistry
José Antonio Rodriguez - Geology
M^a Luisa Quesada - Geochemistry
Agustina Ahijado - Geology
Francisco Matute - Electronics technician
Concepción Duch - Computer, secretary
Eloy Rodríguez - Laboratory operator
Salvador Pons - Laboratory operator

VOLCANOLOGY

A study has been completed of the unusually long and high magnitude basaltic fissural 1730-36 eruption of Lanzarote (Carracedo and Rodríguez Badiola, 1991). Geological (1:25.000) and hazard mapping of this event have been prepared (Carracedo et al., 1992). The main volcanic hazards at present in the Archipelago seem to be related to active, structural rift-type zones (SRTZs), locally called "dorsales" ("ridges"). The study and geological and hazard mapping of the most active SRTZs in recent times in the Archipelago, the Cumbre Vieja ridge of La Palma, is in course.

GEOPHYSICS

Seismology

The seismic network of the Volcanological Station has been designed to study and monitor volcanic activity in the Canary Islands. It is presently composed of five analog telemetered 3-component and four 1-component short-period permanent stations.

In Tenerife, four vertical-component short-period permanent stations and a 3-component station working at the base of Teide volcano since 1987 form the network intended to study and monitor the Teide complex and the North-East and North-West active rifts. In the island of La Palma, a 3-component station is located at the center of the North-South active rift (Cumbre Vieja ridge). Three-component stations are located also in the islands of Gran Canaria, El Hierro and Lanzarote.

The radio telemetered (UHF) analog signals are received at the Volcanological Station where the processing is carried out by the PC-based system with real-time acquisition and off-line data analysis developed at the US Geological Survey and distributed by the International Association of Seismology and Physics of the Earth's Interior (IASPEI) in the IASPEI Software Library. The time signal is provided by a GPS based clock.

Enlargement of the network with four portable 3-component digital stations is scheduled into the current project to eventually complement the permanent seismic network for local close-up observations and in case of eruptive crises.

Geothermal temperatures

Surficial temperatures are periodically measured at fixed points at thermal anomaly fields (Timanfaya, Lanzarote), fumaroles (crater of Teide, Tenerife). Underground temperatures are also periodically measured at accessible water galleries under Teide complex. Thermocouples are used on 1-2 m fixed tubes and a 13 m bore-hole (613°C) in Timanfaya. A data acquisition system is used for prolonged recording periods in a fumarole at Teide volcano.

Ground deformation

A 600 m deep bore-hole is being drilled by the Water Management Department of the Canarian Government at the base of Teide. The Volcanological Station has been granted permission to install a permanent telemetered tiltmeter at the bottom of this bore-hole.

Geomagnetism and paleomagnetism

Periodic monitoring of temporal changes in the total geomagnetic field at fixed points is carried out using a proton precession magnetometer.

Continuous digital recording of the vertical component of the geomagnetic field is carried out at the base of Teide using a fluxgate system.

A complete paleomagnetism laboratory (1986) uses short period paleomagnetic techniques (Secular Variations, Paleointensities) in dating subhistoric volcanism.

GAS AND FLUID GEOCHEMISTRY

Characterization of the chemical and isotopic signatures of the volcanic gases from Canarian volcanoes was carried out during 1991 (Pérez et al, 1992a, 1992b). The results show high emission of ³He/⁴He R/Ratm for Teide (Tenerife) and Taburiente (La Palma) volcanoes, while very low values, close to atmospheric air, were detected for Timanfaya (Lanzarote) and Teneguía (La Palma) volcanoes. Fumarolic activity shows high molar ratios C/S and isotopic ratios ¹³C/¹²C typical of magmatic values for Taburiente and Teide volcanoes. Subsurface ²²²Rn measurements by gamma spectrometry show an enrichment of Rn emanation close to the active SRTZ (Soler et al., 1991). Monitoring of subsurface gas ²²²Rn reveals a modulation between the flux of gas and daily changes in the barometric pressure (Soler et al., 1992). A soil gas ²²²Rn and volatile hydride element (As, Hg, Sb, Bi) survey was carried out during the summer of 1992 to be able to identify some active geo-structures at Las Cañadas caldera in Tenerife.

A new geochemical monitoring program will start in 1993. Fumarole gases from Teide and Taburiente volcanoes will be collected and analyzed monthly. Water samples will be collected from a new bore-hole located at the base of Teide volcano to measure hydro-geochemical signatures. Long term monitoring of soil gas ²²²Rn and its relation to these active volcanic structures (SRTZ) and seismicity are being carried out. The track-etch method is used in four stations in Tenerife and three in La Palma. Continuous measurements of H₂, ²²²Rn, CO₂, Hg and He in the bore-hole located at the base of Teide volcano is projected to start in 1994.

COMMUNICATION NETWORK

Radio link communication facilities are provided by permanent connection of the Volcanological Station to the Environmental Protection Department of the Canarian Government fire prevention and civil protection radio network covering the entire Archipelago.

Further reading :

The 1730-1736 eruption of Lanzarote : an unusually long, high magnitude fissural basaltic eruption in the recent volcanism of the Canary Islands. J.C. Carracedo, E. Rodríguez Badiola and V. Soler (1992). J. Volcanol. & Geotherm. Res., 53: 239-250.

La Erupción de Lanzarote de 1730. J.C. Carracedo y E. Rodríguez Badiola (1991). Servicio de Publicaciones del Cabildo Insular de Lanzarote, 215 pp. (with a color, 1:25.000 geological map of the eruption).

Optimum station distribution to monitor seismic activity of Teide Volcano, Tenerife, Canary Islands. M. García-Fernandez, A. Kijko, J.C. Carracedo and V. Soler (1988). J. Volcanol. Geotherm. Res., 35, pp 195-203.

A seismic monitoring network for volcanic surveillance in Canary Islands: preliminary results from a test telemetric station. ESF meeting on Canarian Volcanism. Lanzarote.

Radon in galleries related to volcanic activity in the island of Tenerife, Canary Islands. V. Soler, J.C. Carracedo, J. Coello, J. de La Nuez, C. Martin and E. RodrÍguez Badiola. Internat. Conf. on Active Volcanoes and Risk Mitigation, Napoli, 1991 (vol. abstracts).

Information updated March 2003