Cumbre Vieja

I got this on 11/6/02. It was not dated but probably appeared by Sept. 2001.

I wonder if Dubya has seen it?
Or, would even understand it if he did?

Funders: CSIC, Spain, and Gobierno de Canarias, Spain

Project holder: Estacion Volcanologica de Canarias (project leader: Dr. J.C. Carracedo)

Principal BGHRC researcher: Simon Day

Duration: three years (1994 - 1997)>

The Cumbre Vieja volcano forms the southern third of the island of La Palma and is the most active volcano in the Canary Islands. It is a complex oceanic island volcano with a large number of volcanic vents and phonolite lava domes organised into volcanic rift zones whose geometry has varied through time. This project involved detailed mapping of the volcano to define this evolution and in particular to determine whether it reflected the onset of instability of the western flank of the volcano. High precision K-Ar radiometric dating of rocks from the Cumbre Vieja (by Dr. H. Guillou, Centre des Faibles Radioactivites, CEA - CNRS, Gif - sur - Yvette, France) has been used to establish the time framework for the study.

For most of its history of growth (beginning before about 125 000 years ago) the Cumbre Vieja volcano was characterised by a triple radial volcanic rift system ("Mercedes star geometry", Carracedo et al. 1999). However, beginning at about 20 000 years ago but primarily around 8000 years ago, the volcano underwent rift zone reorganisation with the development of a dominant N-S trending rift zone along its crest. This zone is inferred to form the headwall region of an unstable block which includes most of the western flank of the volcano and is moving seawards to the rest. This interpretation also accounts for the more recent history of the volcano, up to and including the development of west - facing normal faults along the crest during the last summit - region eruption in 1949. The western flank of the volcano moved seawards by as much as 4 m along these faults. This fault system is inferred to form the first surface rupture associated with a developing fault system which will fail in a large - scale lateral collapse in the future, most probably during another eruption close to the summit of the volcano. A "future history" scenario for such an event and its consequences is described in Apocalypse (W.J. McGuire). Geodetic monitoring of the Cumbre Vieja is presently being carried out at intervals by other members of the Centre.

Papers:

Guillou, H., Carracedo, J.C. & Day, S.J. (1998). Dating of the Upper Pleistocene – Holocene volcanic activity of La Palma using the unspiked K-Ar technique. Journal of Volcanology and Geothermal Research 86, 137 – 149.

Carracedo, J.C., Day, S.J., Guillou, H. & Gravestock, P (1999). The later stages of the volcanic and structural evolution of La Palma, Canary Islands: The Cumbre Nueva giant collapse and the Cumbre Vieja Volcano. Geological Society of America Bulletin 111, 755 - 768.

Day, S.J., Carracedo, J.C., Guillou, H. & Gravestock, P. Recent structural evolution of the Cumbre Vieja volcano, La Palma, Canary Islands: volcanic rift zone reconfiguration as a precursor to volcano flank instability? Journal of Volcanology and Geothermal Research (thematic set Deformation and Flank Instability of Oceanic Island Volcanoes: A Comparison of Hawaii with Atlantic Island Volcanoes), in press.