Canary Islands, Geology / Cape Verde Islands / Caves As Volcanic Province
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SEE ALSO THE FOLLOWING ARTICLES Canary Islands) to the northeast, they form the Canary Azores / Canary Islands, Geology / Cape Verde Islands / Caves as volcanic province. Volcanism in this ∼-km-long Islands / Fossil Birds / Madeira and ∼-km-wide volcanic belt (located at –° N and –° W) decreases in age from the northeast FURTHER READING (Lars Seamount, million years) to the southwest Bacallado, J. J., G. Ortega, G. Delgado, and L. Moro. La fauna de (Hierro Island, million years) and is interpreted to Canarias. Santa Cruz de Tenerife and Las Palmas de Gran Canaria, represent the Canary hotspot track (Fig. ). The Canary Canary Islands: Gobierno de Canarias, Consejería de Medio Ambiente y Ordenación Territorial, Centro de la Cultura Popular Canaria. volcanic province is located on Jurassic ocean crust Bramwell, D., and Z. Bramwell. Wild fl owers of the Canary Islands, (∼ million years old beneath the western part of the nd ed. Madrid: Editorial Rueda. province to ∼ million years old beneath the eastern Brito, A., P. J. Pascual, J. M. Falcón, A. Sancho, and G. González. Peces de las Islas Canarias: catálogo comentado e ilustrado. La Laguna, part of the province), and contains some of the oldest Canary Islands: Francisco Lemus Editor. ocean crust preserved in ocean basins. Fernández-Palacios, J. M., and J. L. Martín, eds. Naturaleza de las Islas Canarias: ecología y conservación. Santa Cruz de Tenerife, Canary GEOLOGICAL OVERVIEW OF THE EVOLUTION Islands: Publicaciones Turquesa. OF THE ISLANDS Haroun, R., M. C. Gil-Rodríguez, and W. Wildpret. Plantas mari- nas de las Islas Canarias. Talavera de la Reina, Spain: Canseco. The morphology of the Canary volcanic province show Izquierdo, I., J. L. Martín, N. Zurita, and M. Arechavaleta, eds. systematic changes from southwest to northeast, refl ect- Lista de especies silvestres de Canarias (hongos, plantas y animales terrestres) 2004. La Laguna, Canary Islands: Consejería de Medio Ambiente y ing an increase in age (Figs. and ) and a change in Ordenación Territorial, Gobierno de Canarias. evolutionary stage. As the volcanoes age, they originally Juan, C., B. C. Emerson, P. Oromí, and G. M. Hewitt. Coloniza- go through a constructive phase of evolution in which tion and diversifi cation: towards a phylogeographic synthesis for the growth of the edifi ce through volcanic activity outpaces its Canary Islands. Trends in Ecology and Evolution : –. Machado, A. Biodiversidad: un paseo por el concepto y las Islas Canarias. Santa Cruz de Tenerife, Canary Islands: Cabildo Insular de Tenerife. Azores-Gibraltar Fracture Zone15˚W 10˚W Martín, A., and J. A. Lorenzo. Aves del archipiélago Canario. La Iberia Laguna, Canary Islands: Francisco Lemus Editor. Moro, L., J. L. Martín, M. J. Garrido, and I. Izquierdo, eds. Lista 200 km de especies marinas de Canarias (hongos, plantas y animales terrestres) 2003. La Laguna, Canary Islands: Consejería de Medio Ambiente y Atlantic Ormonde Ordenación Territorial, Gobierno de Canarias. Ocean (65-67 Ma) Madeira-Tore Rise 3000 35˚N Madeira Ampère & Coral Unicorn Patch (31 Ma) Volcanic (27 Ma) Province Seine (22 Ma) Lars 3000 Porto Santo (68 Ma) (14 Ma) CANARY ISLANDS, Madeira (>5 Ma) Anika (55 Ma) GEOLOGY 2000 Dacia Nico Canary (47 Ma) Conception KAJ HOERNLE Selvagens Bank Volcanic (30 Ma) 30˚N Province Leibniz Institute for Marine Sciences (IFM-GEOMAR), Tenerife 1000 Kiel, Germany (12 Ma) Lanzarote La Palma Fuerteventura Africa (4 Ma) (24 Ma) JUAN-CARLOS CARRACEDO Hierro Gran Canaria (1 Ma) Gomera Estación Volcanológica de Canarias, Tenerife, Spain (9 Ma) (15 Ma) The Canary Islands, located between and km FIGURE 1 Bathymetric map showing the Canary (red) and Madeira from the coast of northwestern Africa (Morocco), (blue) volcanic provinces, including islands and associated seamounts, consist of seven major volcanic islands forming a rough in the eastern central North Atlantic. Thick dashed lines mark centers of west-southwest to east-northeast trending archipelago. possible hotspot tracks. For clarity, only depth contours above 3500 m are shown. Bathymetric data from Smith and Sandwell (1997); ages Together with the Selvagen Islands and a group of seven and location of the Azores–Gibraltar fracture zone from Geldmacher major seamount complexes (some of which were former et al. (2005) and Guillou et al. (1996). CANARY ISLANDS, GEOLOGY 133 Gillespie08_C.indd 133 4/7/09 4:22:34 PM 80 all of the islands have had Holocene acitivity except La 70 Lr Gomera and Fuerteventura. The islands of La Palma, Tenerife, and Lanzarote have had historical volcanic activ- 60 Shield Stage A Late Stage D ity, and thus youthful volcanic structures can be found 50 C Plate velocity across the entire archipelago, even on the oldest islands. ? 40 = 12 mm/yr Lz The two youngest and westernmost islands of Hierro F Age (Ma) S ? 30 ( m above sea level, with oldest dated subaerially erupted rocks at . million years) and La Palma ( m; 20 GC T . million years old) have been the most active within G 10 LP the Holocene. Both volcanic islands are characterized by H 0 mafi c alkaline volcanism, high eruptive rates, and volca- 0 100 200 300 400 500 600 700 800 nism along magmatic rift zones, commonly associated Distance from Hierro Along Hotspot Track (km) with the shield cycle of volcanism on ocean island volca- FIGURE 2 Radiometric ages of shield stages and late (rejuvenated noes. Both volcanoes (and associated islands) are expected or posterosional) stages of magmatic activity on islands and sea- mounts in the Canary volcanic province versus distance from Hierro. to continue to grow in size in the future. The center of each island is projected onto the proposed curved hot- The three central islands, intermediate in age, were spot track in Fig. 1 along a line perpendicular to the hotspot track. Dis- in their shield stage in the Middle to Late Miocene and tances were measured from Hierro along the proposed hotspot track. The regression line calculated for oldest available ages of shield-stage have had low levels of late or rejuvenated volcanism in the volcanism gives an average rate of plate motion of 12 mm/year. On Pliocene and/or Quaternary. Tenerife in the central west- older islands and seamounts, volcanic units that had low 206Pb/204Pb ern part of the archipelago forms the largest island and ≤ ( 19.5) were assigned to the late stage of volcanism, with the excep- is also the third largest and highest (more than m tion of the single sample from Lars seamount, which had a slightly lower 206Pb/204Pb (19.44). Abbreviations for islands and seamounts: in elevation above the sea fl oor and m in elevation H = Hierro, LP = La Palma, G = Gomera, T = Tenerife, GC = Gran Canaria, above sea level; . million years old) volcanic structure S = Selvagen Islands, F = Fuerteventura, Lz = Lanzarote, C = Conception on Earth after the Hawaiian volcanoes of Mauna Loa and seamount, D = Dacia seamount, A = Anika seamount, and Lr = Lars seamount. References for age data from Guillou et al. (1996) and Mauna Kea. The highest peak of Tenerife is formed by the Geldmacher et al. (2005). highly differentiated (phonolitic) Teide volcano, nested in a lateral collapse caldera (formed through mass wasting), destruction through mass wasting (e.g., landsliding) and indicating that this volcano is at the transition from its erosion. The constructive phase occurs primarily during constructive to destructive phase. Considering the signifi - the shield-building (or shield) cycle of activity, during cantly lower eruption rates of the Canaries as compared which eruptive rates are high, and most of the volcanic to the Hawaiian volcanoes, the similarity in size refl ects edifi ce is formed. Even though mass wasting is an impor- Tenerife’s older age (longer life-span), most likely related tant process during the shield stage, the volcano contin- to the almost-order-of-magnitude slower motion of the ues to increase in size, despite short-term setbacks. The plate beneath the Canary Islands (∼ mm/year) as com- constructive phase of island/volcano evolution can extend pared to the motion of the plate beneath the Hawaiian into the fi rst late (also commonly referred to as post-ero- Islands. Therefore, it has taken much longer for Tenerife sional or rejuvenated) cycle of volcanism, during which to move away from its magmatic source than has been volcanic eruptive rates are drastically lower, but magmas the case with the Hawaiian volcanoes. Although crudely can be more evolved (silicious and thus more viscuous), round in outline, the central volcanoes of La Gomera contributing to an increase in volcano height. Late cycles ( m; . million years old) and Gran Canaria ( m; of volcanism are generally separated from the shield stage . million years old) no longer have conical shapes and of volcanism by extended periods of volcanic inactivity or are characterized by deeply incised canyons, indicating drastically reduced activity. During the destructive phase that these two volcanoes are well into their destructive of evolution, mass wasting and erosion outpace volcanic phase of evolution, with erosion and mass wasting out- growth, and the volcanoes (islands) decrease in size until pacing growth through magmatic activity. Erosion has they are eroded to sea level. As the plate moves away from exposed intrusive complexes and dike swarms on both the magma source, it cools and subsides, and the now islands. The compositions of volcanic rocks are highly fl at-topped volcanic edifi ces sink beneath sea level, form- variable, ranging from mafi c (transitional tholeiite to meli- ing guyots. Despite the differences in age of the volcanoes, lite nephelinite) to highly evolved (peralkaline rhyolite to 134 CANARY ISLANDS, GEOLOGY Gillespie08_C.indd 134 4/7/09 4:22:35 PM trachyte to phonolite), refl ecting the mature nature of in the geological past of the Canarian archipelago, only these volcanoes.