No abstract

The Canarian Archipelago is a group of volcanic islands on a slow-moving oceanic plate, close to a continental margin. The origins of the archipelago are controversial: a hotspot or mantle plume, a zone of lithospheric deformation, a region of compressional block-faulting or a rupture propagating westwards from the active Atlas Mountains fold belt have been proposed by different authors. However, comparison of the Canarian Archipelago with the prototypical hotspot-related island group, the Hawaiian Archipelago, reveals that the differences between the two are not as great as had previously been supposed on the basis of older data. Quaternary igneous activity in the Canaries is concentrated at the western end of the archipelago, close to the present-day location of the inferred hotspot. This is the same relationship as seen in the Hawaiian and Cape Verde islands. The latter archipelago, associated with a well-defined but slow-moving mantle plume, shows anomalies in a plot of island age against distance which are comparable to those seen in the Canary Islands: these anomalies cannot therefore be used to argue against a hotspot origin for the Canaries. Individual islands in both archipelagoes are characterized by initial rapid growth (the ‘shield-building’ stages of activity), followed by a period of quiescence and deep erosion (erosion gap) which in turn is followed by a ‘post-erosional’ stage of activity. The absence of post-shield stage subsidence in the Canaries is in marked contrast with the major subsidence experienced by the Hawaiian Islands, but is comparable with the lack of subsidence evident in other island groups at slow-moving hotspots, such as the Cape Verdes. Comparison of the structure and structural evolution of the Canary Islands with other oceanic islands such as Hawaii and Réunion reveals many similarities. These include the development of triple (‘Mercedes Star’) rift zones and the occurrence of giant lateral collapses on the flanks of these rift zones. The apparent absence of these features in the post-erosional islands may in part be a result of their greater age and deeper erosion, which has removed much of the evidence for their early volcanic architecture. We conclude that the many similarities between the Canary Islands and island groups whose hotspot origins are undisputed show that the Canaries have been produced in the same way.

The Teide and Pico Viejo stratocones and the Northwest and Northeast Rifts are products of the latest eruptive phase of the island of Tenerife, initiated with the lateral collapse of its northern fl ank that formed the Las Cañadas Caldera and the Icod-La Guancha Valley ca. 200 ka. The eruptive and structural evolution of this volcanic complex has been reconstructed after detailed geological mapping and radioisotopic dating of the signifi cant eruptive events. A set of 54 new 14 C and K/Ar ages provides precise age control of the recent eruptive history of Tenerife, particularly Teide Volcano, the third-highest volcanic feature on Earth (3718 m above sea level, >7 km high), and unique in terms of its intraplate setting. The development of the Teide-Pico Viejo Volcanoes may be related to the activity of the Northwest and Northeast Rifts. Volcanic and intrusive activity along both rift zones may have played an important role in activating the gravitational landslide and in the subsequent growth, nested within the collapse embayment, of an increasingly higher central volcano with progressively differentiated magmas. The coeval growth of the central volcano with sustained activity along the rifts led to a clear bimodal distribution in composition of eruptive products, with the basaltic eruptions in the distal part of the rifts and phonolitic and more explosive eruptions in the central area, where the differentiated stratocones developed. Current volcanic hazard in Tenerife is considered to be moderate, because eruptive frequency is low, explosivity is modest, and the eruptive activity of the Teide stratocone seems to have declined over the past 30 k.y., with only one eruption in this period (1150 yr B.P.).

The Canarian archipelago comprises seven main volcanic islands and several islets that form a chain extending for c.

La isla de Lanzarote, situada en el extremo oriental de la alineación del punto caliente de las Canarias, ha tenido escasa actividad eruptiva de rejuvenecimiento en el Holoceno, posiblemente reducida a las erupciones de 1730 y IS24, hecho que concuerda con el avanzado estado post-erosivo de la isla. La datación de la erupción del Volcán Corona, aparentemente el evento volcánico anterior en Lanzarote a las erupciones históricas, ha dado una edad media ponderada 40Arp9Ar de 21 ± 6,5 ka. Esta edad concuerda con las observaciones geológicas, particularmente las circunstancias de formación del tubo volcánico de 7,6 km de longitud y hasta 25 m de diámetro que se formó en las primeras fases de la erupción. El último tramo de 1,6 km está sumergido, finalizando a una profundidad de > SO m. Nuestra interpretación es que el tubo volcánico activo no pudo alcanzar esa profundidad circulando por un medio subacuático, sino que fluyó por una plataforma costera al menos 1,6 km más extensa y al menos SO m más baja que la costa actual, circunstancia que sólo ha podido darse en coincidencia con un pronunciado descenso del nivel marino en un máximo glacial, con toda probabilidad el último, hace unos 20 ka. La subsiguiente transgresión inundó el tubo hasta el nivel actual. La edad de la erupción queda pues limitada por las edades radioisotópicas en 21 ± 6,5 ka y, concordantemente, por el máximo descenso del nivel marino, registrado entre unos IS y 21 ka. El estudio de la erupción del Corona establece hitos importantes en la historia volcánica de la isla de Lanzarote y aporta evidencia significativa de los cambios del nivel marino ocurridos en las Canarias en relación con las glaciaciones.