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Home , Cabildo insular, Canary hotspot, Canary Islands, El Hierro, Lanzarote, Teide

SEE ALSO THE FOLLOWING ARTICLES ) to the northeast, they form the Canary / Canary Islands, Geology / Islands / Caves as volcanic province. Volcanism in this ∼-km-long Islands / Fossil Birds / 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 and de , represent the Canary 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. : 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. , Canary GEOLOGICAL OVERVIEW OF THE EVOLUTION Islands: Publicaciones Turquesa. OF THE ISLANDS Haroun, ., M. C. Gil-Rodríguez, and W. Wildpret. . Plantas mari- nas de las Islas Canarias. Talavera de la Reina, : 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: Insular de Tenerife. Azores- Fracture Zone15˚W 10˚W Martín, A., and J. A. Lorenzo. . Aves del archipiélago Canario. La 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 & 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, (12 Ma) (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 (), (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 -southwest to east-northeast trending . 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 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 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 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 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 and seamount, D = Dacia seamount, A = Anika seamount, and Lr = Lars seamount. References for age data from Guillou et al. (1996) and . The highest peak of Tenerife is formed by the Geldmacher et al. (2005). highly differentiated (phonolitic) , nested in a lateral collapse (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 the case with the Hawaiian volcanoes. Although crudely can be more evolved (silicious and thus more viscuous), round in outline, the central volcanoes of 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 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 to ), refl ecting the mature nature of in the geological past of the Canarian archipelago, only these volcanoes. moderately explosive activity (strombolian to subplinian) On the two easternmost, oldest, and lowest islands took place in the last , years. Holocene eruptions, of Fuerteventura ( m; . million years old) and predominantly basaltic fi ssure eruptions, occurred on all Lanzarote ( m; . million years old), erosion is the islands except La Gomera and Fuerteventura. Most of clearly the main process shaping the morphology of the these, however, have been located on La Palma, , islands, even though both islands have had rejuvenated and Tenerife, with only – events on Gran Canaria volcanism within the last , years, and Lanzarote during this period and two on Lanzarote (– and even within historical times. Both islands are realtively ). The most recent eruption in the Canary Islands was fl at, with little of the original morphol- in , from the Teneguia volcano at the southern tip of ogy being preserved. Instead, they are characterized by iso- La Palma. During the Holocene, phonolitic strombolian lated older volcanic sequences or erosional remnants and to subplinian eruptions were associated with dome broad valleys. Surprisingly, the largest historical eruption growth in the Teide volcanic complex on Tenerife, and to in the Canary Islands and the second largest basaltic fi ssure a lesser extent on the rift on La Palma. eruption ever recorded (after the  Laki eruption on Ice- No casualties have been reported in the  eruptions land) was the – Timanfaya eruption on Lanzarote, recorded after the colonization of the archipelago at which produced ∼ km of primarily tholeiitic . the end of the sixteenth century. Reliable prediction of when future eruptions will occur is not feasible because AGE OF VOLCANISM of the low frequency of events and great variability of The age of volcanism in the Canary Islands is well known inter-eruptive periods, from a few years to several hun- from radiometric age dating. More than  K/Ar, Ar/ dred years (e.g., on Cumbre Vieja, the most active vol- Ar, and C ages have been obtained by different groups cano in the historic epoch, repose periods varied from on igneous samples from the islands. There have been a  to  years). number of problems, however, primarily in dating older volcanic rocks and the uplifted portions of the seamount GEOCHEMICAL OVERVIEW OF formations, some of which are clearly affected by altera- ISLAND EVOLUTION tion. Samples with excess Ar have produced ages that are The geochemistry of the volcanic rocks from the Canary too old, artifi cally increasing the duration of the basaltic Islands is well understood in the context of volcano shield stage on the islands. Ages obtained by newer tech- evolution. During each growth cycle (shield and late niques, such as Ar/Ar step heating, single crystal laser age cycles), highly silica undersaturated rocks (nephelinites dating, and the K/Ar unspiked method, and the employ- and basanites) dominate the early stage, more silica- ment of stringent age-dating requirements (e.g., sampling saturated basaltic melts (alkali basalts and transitional from well-controlled stratigraphic sections, and perform- thoeleiites) are produced during the peak of the cycle, ing replicated analyses and systematic comparison of the and both mafi c and evolved alkalic volcanic rocks (alkali palaeomagnetic polarities of the samples with the currently basalts–basanites–nephelinites to –) accepted geomagnetic reversal timescales) demonstrate are erupted during the waning stages. The almost com- that there is a progression of increasing age of the shield plete lack of tholeiitic rocks and the low eruption rates stage of volcanism from west to east in the Canary archi- during shield-cycle volcanism on the Canary volca- pelago and from southwest to northeast in the Canary vol- noes is likely to refl ect a combination of low sublitho- canic province, even though most of the Canary volcanoes spheric (mass fl ux) rates of the Canary plume have had a very long, complicated history, often including and deep depths of melting beneath the thick Jurassic multiple cycles of late-stage volcanism (Figs.  and ). oceanic lithosphere. Although there are no systematic differences in major and trace element composition, sys- VOLCANIC HAZARDS tematic variations in isotopic composition do exist, with Geological hazards are moderate in the Canary Islands shield-stage volcanism being generally characterized by compared, for instance, with the Hawaiian Islands, higher Pb and Sr and lower Nd and Hf isotopic ratios as which have a similar and population but much more compared to late-stage volcanism. These differences are frequent and intense volcanic activity and seismicity. likely to refl ect greater amounts of melting of depleted Although high magnitude eruptions (plinian) occurred upper or plume type mantle during the late stages of

CANARY ISLANDS, GEOLOGY 135

Gillespie08_C.indd 135 4/7/09 4:22:35 PM volcanism, as compared to enriched plume material dur- years old, but there is continuing controversy about the ing the shield stage of volcanism. validity of these fossil ages. The oldest subaerial volcanism is separated from the GEOLOGY OF THE INDIVIDUAL underlying submarine volcanics by an angular uncon- CANARY ISLANDS formity and a –-m-thick sedimentary unit made El Hierro up of breccias, agglomerates, and sediments. During the The youngest and smallest of the Canary Islands is Taburiente stage of volcanism, continuous mafi c alkaline formed by three overlapping Quaternary stages of pri- eruptive activity formed a -m-high shield volcano. marily mafi c alkaline volcanism from oldest to youngest: Subsequent volcanism migrated southward along the Tiñor, El Golfo, and Rift (Fig. ). A prominent three- southern Cumbre Nueva . Continuing southward branched rift system and related arcuate lateral collapse migration of volcanism ultimately resulted in the extinc- embayments ( scars) between the rifts defi ne tion of the northern shield ∼. million years ago and in the characteristic shape of the island. Four lateral col- the formation in the last , years of the Cumbre lapses have been recognized on El Hierro. The Tiñor Vieja rift zone, a -km-long, -m-high ridge, com- collapse (∼.-million-year-old) embayment in the north- posed predominantly of mafi c alkaline . western part of the island was rapidly fi lled by subse- Half of the historical (i.e., occurring in the last  years) quent volcanism, developing a -m-high, -km- eruptions of the Canary Islands, including the most recent wide volcano that collapsed (between , and event in , occurred along the Cumbre Vieja rift sys- , years ago) to form the present El Golfo embay- tem (Fig. ). These eruptions have been characterized by ment. The El Julan lateral collapse (occurring more than Strombolian activity forming cinder cones and lava fl ows. , years ago) removed the southwestern fl ank of The  eruption added several square kilometers of new the island, whereas the incomplete failure of the south- land to the island, clearly demonstrating that the island is eastern fl ank (between ∼, and , years ago) still growing. Phonolites have been extruded in several of generated the San Andrés fault system and the Las Playas the historical eruptions and can form from basanitic paren- slump. The latest eruptive activity of El Hierro, occur- tal magmas within – years. The  eruption is ing over the last ∼, years, forms a conspicuous famous for the emplacement of giant phonolitic spines (tens three-branched rift system, capping most of the island of meters high), which, according to an eyewitness account with eruptive vents (at the rift crests) and lava fl ows (at of a monk, rose from the ground like “the devil’s horns” at the fl anks), partially fi lling the respective collapse embay- the beginning of the almost exclusively mafi c eruption. ments. The last eruption on the island, from a small vent on the northeastern rift, was dated by C at  years La Gomera ago. An intense seismic crisis, believed to be related to an La Gomera, presently undergoing a volcanic hiatus, is impending eruption, almost caused the total evacuation a heavily eroded, circular ( km in diameter) volcano of the island in . (Fig. ). During the Late Miocene, the mafi c alkaline shield volcano (∼– million years old) experienced a La Palma northward lateral collapse. Continued volcanic activity La Palma, the most active island of the Canaries in the fi lled the collapse embayment and spread over the entire Holocene, is formed by two coalesced volcanoes: the island, forming a central volcano with differentiated rocks northern circular Taburiente Volcano and the younger at its terminus. The remains of a central caldera in this north–south elongated Cumbre Vieja volcano to the south volcano crop out north of Vallehermoso, comprising (Fig. ). Two lateral collapses removed much of the south- trachytic and phonolitic lavas and intrusives with the lat- western fl ank of the Taburiente volcano. The uplifted (by ter forming radial dike swarms and cone sheets. A local about  m) and tilted Pliocene seamount formations unconformity separates the late-cycle Pliocene (occurring are exposed on the fl oor and walls of the Caldera de primarily – million years ago) mafi c alkaline eruptions Taburiente, formed by the younger gravitational land- from the Miocene shield. Numerous phonolitic domes, slide (∼. million years ago). The seamount volcanism is some of the most conspicuous and spectacular volcanic fea- composed of basaltic to trachytic pillow lavas and hyalo- tures of the island, intrude both the Miocene and Pliocene clastites. Fossils in submarine sequences suggest that the mafi c sequences. Volcanic activity was sparse during the uplifted portion of the seamount stage may be – million last  million years and ended completely on the island

136 CANARY ISLANDS, GEOLOGY

Gillespie08_C.indd 136 4/7/09 4:22:35 PM EL HIERRO Sediments (alluvial Platform-forming Holocene and scree deposits) eruptions RIFT Lateral collapse Last Glacial Maximum Upper VOLCANISM Collapse escarpment NNE RIFT ZONE Pyroclastics - <145 ka Caldera rim forming (35 ) Lavas eruptions Fault El Golfo gravitational collapse Airport EL GOLFO NW RIFT Rift Trachytes ZONE Lower and Middle VOLCANISM Pleistocene Basalts (545-158 ka) VALVERDE Ti“ or gravitational collapse San Andr»s Lower and Middle TIó OR VOLCANISM fault

Pleistocene (1.2-0.88 Ma) PLEISTOCENE-QUATERNARY EL GOLFO TIó OR

SAN ANDRÖS 6 ka 2.5 ± 0.07 ka FRONTERA 1000 WNW RIFT ZONE 500 (275 )

Malpaso (1500 m) N 1000 LAS PLAYAS 500

EL JULAN EL HIERRO

NW RIFT 0 5 km ZONE NE RIFT ZONE

500 1000 LA RESTINGA 1500 2426 m 2000 SSE RIFT Roque de ZONE Los Muchachos (155 ) Caldera de 18 17 16 15 14 13 Taburiente N 29 LA PALMA 29 N Lanzarote Tenerife

28 Fuerteventura 28 La Gomera e EL HIERRO Gran Canaria AFRICA 1480 AD 18 17 16 15 14 13 W 6±2 ka LA PALMA 1949 Historical volcanism CUMBRE 1.04±0.09 ka VIEJA Holocene volcanism 1585 ? VOLCANO 1949 Upper Pleistocene volcanism (<150 ka) 1712 1500 BEJENADO 1000 500 (0.56-0.49 ma) LA PALMA VOLCANISM ? gravitational landslide 0 5 10 k Upper (0.78-0.41 ma) TABURIENTE 1644 Lower (1.08-0.78 ma) VOLCANISM 3.2±0.1 ka gravitational landslide GARAF’A (1.77-1.20 Ma) VOLCANISM 1677 General discordance 1971 PLIOCENE-QUATERNARY Pillow lavas, SEAMOUNT VOLCANISM CUMBRE dikes and VOLCANO TABURIENTE VIEJA (PLIOCENE) RIFT ZONE intrusives

FIGURE 3 Simplifi ed geological map of the western Canaries: El Hierro and La Palma. Modifi ed from Carracedo et al. (2002).

. million years ago, the age of the younger intra-canyon on Tenerife correspond to three deeply eroded mafi c lavas located south of the capital San Sebastián. alkaline massifs: the Central, Anaga, and Teno shield volcanoes. The Central shield, the fi rst to develop, is at Tenerife present covered by later volcanism, with the exception of The triangular-shaped island of Tenerife is the largest and some outcrops in the southern fl ank of the island (the highest in the Canarian archipelago and has a complex Roque del Conde ). The shield stage of the island volcanic history (Fig. ). The oldest visible volcanic rocks was completed with the growth of two new volcanoes, the

CANARY ISLANDS, GEOLOGY 137

Gillespie08_C.indd 137 4/28/09 1:41:43 PM LA GOMERA LA GOMERA

Periclinal basalts (5.4-4.2 Ma) N Vallehermoso Phonolitic domes PLIOCENE VOLCANISM Horizontal basalts (5.4-4.2 Ma)

Cone sheet 005 001 00000 Felsic central 10 volcano MIOCENE LATERAL COLLAPSE VOLCANISM 14814878787m m Mafic Shield volcanism (9.4-8.0 Ma) GarGarajoajonayoonay 00 Plutonic rocks 5 00 00 10

San Valle Sebastián Gran Rey

05 Km ANAGA SHIELD VOLCANO SANTA CRUZ DE TENERIFE

LA OROTAVA TENERIFE

Historical eruptions LATE

00 E PLEISTOCENE- 10 NOZ 1705 Teide volcanic complex 1706 HOLOCENE TFI Rift volcanism VOLCANISM TENO 1909 0 R GÜÍMAR 200 NW E LAS CAÑADAS LATERAL COLLAPSE 200 ka SHIELD 0 003 N 1705 R Cañadas FIT TEIDE VOLCANO 1492 Z (3718m) PlIOCENE- PLEISTOCENE 1798 VOLCANISM Erosion Anaga (4.9-3.8 Ma) MIO-PLIOCENE Teno (6.1-5.1 Ma) SHIELD VOLCANOES

E Central (11.9-8.8 Ma)

NO

ZT

F GRAN CANARIA CENTRAL I R

SHIELD HTUO QUATERNARY VOLCANO TENERIFE Mafic eruptions (<1.3 Ma)

S VOLCANISM 10 km Post Volcanism (3.1-1.7 Ma) PLIOCENE Roque Nublo stratovolcano VOLCANISM (5.6-3.5 Ma)

LAS PALMAS DE Erosion GRAN CANARIA Cone sheet (11.7-7.3 Ma)

Syenitic intrusions (12.3-8.9 Ma) MIOCENE 1000 SHIELD Felsic volcanism (14.0-8.8 Ma) VOLCANISM

Basaltic shield (14.5-14.0 Ma)

Lateral collapse

Caldera rim 1949 m Rift CALDERA DE Sediments

MOGÁN 18º 17º 16º 15º 14º 13º

N 29º La Palma 29º N Lanzarote

TENERIFE GRAN CANARIA GRAN 28º LA Fuerteventura 28º CANARIA GOMERA 0 100 200 km 0 10 km AFRICA 18º 17º 16º 15º 14º 13º W

FIGURE 4 Simplifi ed geological map of the central Canaries: La Gomera, Tenerife, and Gran Canaria. Modifi ed from Carracedo et al. (2002).

Gillespie08_C.indd 138 4/28/09 1:41:44 PM Teno volcano, overlying the western fl ank of the Central outcropping primarily in the southwest of the island, are volcano, and the Anaga volcano, which developed at the alklali basaltic lava fl ows belonging to the shield stage of northeastern part of the island. volcanism (Fig. ). The Miocene basalts are overlain by Late-cyle volcanism took place after – million years up to more than  m of evolved , lavas, of eruptive quiescence and discordantly overlies the and fallout , respresenting the largely explosive Central volcano. In this rejuvenated cycle, a -km-wide, outfl ow facies of the large elliptical, northwest–south- -m-high, progressively differentiated central volcano east trending,  by –km, -m-deep Caldera de (Las Cañadas volcano) developed with contemporaneous Tejeda. The Tejeda caldera may be unique in the Canary basaltic eruptions along a three-arm rift system on the Islands in that it formed by collapse of the summit of fl anks of the Central volcano. Major explosive eruptions the basaltic shield volcano above a large shallow magma from the central volcano formed trachytic ignimbrites, chamber (at a –-km depth). The onset of the collapse pyroclastic fl ows, and ash-fall deposits mantling the south- occurred upon the eruption of the widespread (cover- ern fl ank of the island (the Bandas del Sur formation). ing an area of more than  km), voluminous (∼ About , years ago, the summit of the Cañadas km) P  million years ago, zoned from central volcano collapsed, forming the Caldera de Las rhyolite to trachyte to (from bottom to top). Cañadas and the La Guancha–Icod depressions. Activity The outfl ow facies of the caldera become more silica- on the northeastern and northwestern rift zones may undersaturated in their upper sections (changing from have played an important role in activating this gravi- predominantly peralkaline rhyolites to phonolites), with tational landsliding. This catastrophic event marked the most activity having ended by ∼ million years ago. Alkali onset of the latest eruptive phase in Tenerife, character- syenite intrusives and a spectacular trachytic–phonolitic ized by continued mafi c alkaline activity on the rifts and cone sheet swarm of dikes, which erosion has exposed in by the subsequent growth of the phonolitic Teide central the central part of the island, provide the last evidence volcano, nested within the collapse embayment. Parts of of Miocene magmatic activity lasting to ∼ million years the northeastern rift zone also collapsed to form the La ago. Orotava and Güímar valleys. Late or posterosional volcanism started around Relatively abundant eruptive activity occurred in this . million years ago with the eruption of low volumes of latest volcanic phase of Tenerife. At least  events took nephelinite to basanite lavas and pyroclastic rocks from place during the Holocene, the greater part (%) as monogenetic centers. The Roque Nublo stratovolcano mafi c alkaline fi ssure eruptions on the northwestern and (∼.–. million years old) began with thick sequences northeastern rift zones and % as phonolitic eruptions of mafi c lava fl ows (transitional tholeiite to basanite) fi ll- inside the Caldera de Las Cañadas and on the Teide–Pico ing canyons in the deeply eroded Miocene volcanic edi- Viejo volcanoes, particularly as lava domes and coulees. fi ce. Upsection, the volcanic rocks become more evolved The latest eruption of the Teide volcano (Lavas Negras (ranging primarily from hawaiite to trachyte and tephrite eruption) is generally believed to be the eruption seen by to phonolite) and grade into tuffaceous rocks, massive in  on his way to discovering breccia sheets (representing block and ash fl ows, lahars, America. The radiocarbon age of  ±  years BP, how- and ), and volcanic plugs of highly evolved ever, indicates that this could not have been the eruption hauyne–phyric phonolites such as above Risco Blanco observed by Columbus. The  sighting of Columbus at the head of Barranco de Tirajana. The upper portions probably corresponds to Montaña Boca Cangrejo, a vent of the Roque Nublo group outcrop primarily in the cen- located in the northwestern rift zone with a radiocarbon ter of the island, where the well-known Roque Nublo age of  ±  years BP. The four most recent eruptions monolith, formed from a large breccia block, forms one took place in , , , and . of the highest peaks on the island. The Roque Nublo stratocone is likely to have reached an elevation of more Gran Canaria than  m and thus may have been similar in height to The subaerial evolution of Gran Canaria can be divided the present Pico de Teide volcano on Tenerife. Overlying into three cycles of volcanic activity: a Miocene shield an erosional unconformity in some parts of the island is cycle (∼.–. million years ago) and two late cycles in a package of primarily basanitic to melilite nephelinite the Pliocene (∼.–. million years ago) and Quaternary lava fl ows and dikes (∼.–. million years old), outcrop- (less than . million years ago). The oldest subaerial rocks ping exclusively on the northeastern half of the island. on Gran Canaria (older than .–. million years), Quaternary volcanism (occurring in the last . million

CANARY ISLANDS, GEOLOGY 139

Gillespie08_C.indd 139 4/7/09 4:22:38 PM years), primarily nephelinitic to basanitic in composition, Late-cycle volcanism extended from about . million has been increasing over the last , years, suggest- to , years ago, the time of the last eruption dated ing that Gran Canaria may be entering a new late cycle on the island, although cones in the northern part of the of activity. The youngest dated volcanic structure on island may be younger. Abundant littoral marine fauna the island is the Bandama caldera and strombolian cone developed during Pliocene equatorial climatic phases, and (∼ years old). large volumes of aeolian sands derived from the Sahara covered most of the island at the end of the Pliocene. Fuerteventura Fuerteventura has the oldest exposed rocks of the Canary Lanzarote Islands and is closest ( km) to the African coast, situ- Lanzarote is the continuation to the northeast of Fuerte- ated on up to  km of continental rise sediments derived ventura; these two islands are not geologically different, from Africa. Four main lithological units are exposed on sensu stricto, because they are only separated by a nar- Fuerteventura (Fig. ): () Mesozoic oceanic crust and row stretch of sea, which is shallower (less than  m) sediments, () submarine volcanics and intrusives and than the lowest sea level at maximum glacials. The oldest sediments, () Miocene shield volcanoes, () and late or rocks in Lanzarote correspond to two main basaltic volca- rejuventated Pliocene-Quaternary volcanic rocks and sed- noes, which developed as independent island volcanoes: iments. The Mesozoic oceanic crust, presumably uplifted the southern Ajaches volcano and the northern as a result of extensive intrusive activity, is exposed along volcano (Fig. ). Isotope geochemistry suggests that both the western coast of the island and comprises a thick volcanoes represent late cycles of volcanism, and there- (∼-m) sedimentary sequence of Early Jurassic age fore that the shield cycle forming the bulk of this island with rare ocean crust volcanic rocks. Alkalic volcanic may not be subaerially exposed. After a period of general rocks with ages near the Cretaceous–Tertiary boundary quiescence of about  million years, a new cycle of reju- may be associated with seamount volcanism unrelated to venated activity resumed in the Quaternary with basaltic the formation of the Canary Islands. eruptive centers aligned in the northeast–southwest direc- The submarine volcanic rocks, comprising mafi c pil- tion. The Corona volcanism in the northern part of the low lavas and hyaloclastites, are unconformably overlain island (occurring , ±  years ago) produced one by littoral and shallow-water marine deposits (reefal bio- of the largest known lava tubes, . km long with sections clastic sediments, sandstones, and conglomerates), reaching  m in diameter. The tube formed as the lavas gently tilted to the west and apparently representing advanced along a wave-cut platform located  m below the transition from submarine to subaerial activity. A the present sea level. The last  km of the are at sequence of plutonic and hypabyssal intrusions, includ- present submerged (− m) following sea-level rise after ing an early syenite–ultramafi c formation (alkali pyrox- the last glaciation. enites, amphibolites, and amphibole gabbros intruded by Holocene eruptions are probably limited to the his- syenites) and later ijolite–syenite–carbonatite complexes torical – and  events. During the – (rarely exposed in intraplate island volcanoes), appear to Timanfaya eruption, which lasted for  months, over be associated with the submarine volcanic complex.  volcanic vents, aligned along a -km-long, N ° Beginning about  million years ago, three adjacent E–trending fi ssure, were formed in fi ve main multi-event basaltic shield volcanoes developed: the Central, North- eruptive phases. The Timanfaya eruption began with the ern, and Southern or Jandía shields, comprising mainly eruption of basanite and alkali basalt during the fi rst half- alkali basaltic and trachybasaltic lavas, with minor year and then erupted tholeiite for the rest of the eruption. trachytic differentiates. The extremely dense northeast– In stark contrast to , where tholeiites represent the southwest dike swarm crossing the Miocene shields may most common rock type during the shield stage of volca- be related to crustal stretching of as much as  km. nism but are generally absent in the rejuvenated stage, the Plutonic rocks (pyroxenites, gabbros, and syenites) and late-cycle Timanfaya eruption produced the most tholei- a basaltic-trachybasaltic dike swarm, which represent itic rocks found thus far in the Canary Islands. the hypabyssal roots of the evolving subaerial volcanic complexes, outcrop in the core of both the Central and OTHER VOLCANOES OF THE CANARY Northern shields. Later plutonic activity includes con- VOLCANIC PROVINCE centric intrusions of gabbros and syenites, forming a The Selvagen Islands and neighboring large seamounts, spectacular ring complex. located north and northeast of the Canary Islands, are

140 CANARY ISLANDS, GEOLOGY

Gillespie08_C.indd 140 4/7/09 4:22:38 PM 18º 17º 16º 15º 14º 13º Isla N N 29º LANZAROTE 29º N

Tenerife FUERTEVENTURA La Palma 28º 28º La Gomera Corona Gran Canaria FAMARA Corralejos AFRICA Volcano El Hierro SHIELD VOLCANO 18º 17º 16º 15º 14º 13º W 500 Corona V. lava tube Peñas del Chache LANZAROTE 670 m 500

18241824 500

Puerto del Rosario

1824 1824 Puerto de NORTHERN La Peña SHIELD 500 VOLCANO

500

500 0

50 500 0 10 km

JANDÍA SHIELD FUERTEVENTURA VOLCANO CENTRAL SHIELD VOLCANO LOS AJACHES 500 SHIELD VOLCANO Jandía 0 20 Km 807 m

Morro Jable FUERTEVENTURA

Eolian sands PLIO-QUATERNARY Pleistocene volcanics VOLCANISM LANZAROTE (1.1-0.13 Ma) Pliocene volcanics <5 Ma (5.1-1.9 Ma)

1824 Historic HOLOCENE General erosive unconformity volcanism 1730-1736 VOLCANISM Jandía Shield (15.5-13.7 Ma) MIOCENE Corona-Los Helechos Northern Shield (18.1-14.5 Ma) VOLCANISM group (91-21 ka) 20-13 Ma PLEISTOCENE Central Shield (20.2-13.7 Ma) Central rift and the VOLCANISM Isletas (0.8-0.1 Ma) <1.2 Ma Periferic volcanism Ring complex (1.2-0.8 Ma) Plutonic rocks (PRE-MIOCENE?)

General erosive unconformity Collapse caldera General erosive unconformity FaMara Volcano PRE- to EARLY (10.2-6.3 Ma) MIOCENE Submarine to emergent volcanics, VOLCANISM sediments and intrusives (>30-20 Ma) SUBMARINE Los Ajaches Volcano VOLCANIC 15.6-5.7 Ma Uplifted oceanic crust (Mesozoic) (15.6-5.7 Ma) COMPLEX

FIGURE 5 Simplifi ed geological map of the eastern Canaries: Lanzarote and Fuerteventura. Modifi ed from Carracedo et al. (2002).

located on the same bathymetric high as the Canary can provide clues to the earlier history and origin of the Islands and have similar geochemical (major and trace Canary Islands. element and Sr–Nd–Pb–Hf isotopic) compositions to The Selvagen Islands, located about  km north the Canary Island magmatic rocks, but distinct composi- of the Canary Islands, form the summits of two shield tions from the Madeira Island rocks to the north (Fig. ), volcanoes that ascend from  m water depth, merg- consistent with their derivation from a similar source as ing at depths between  and  m. The main island the Canary Islands. Therefore, these volcanic structures of Selvagem Grande ( m; area of . km) is located are also included in the Canary volcanic province and on the summit of the northeast volcano, and a group of

CANARY ISLANDS, GEOLOGY 141

Gillespie08_C.indd 141 4/7/09 4:22:38 PM small islands, the largest being Selvagem Pequena sphere would only generate very small volumes of melt as ( m; . km), is located on the summit of the sec- a result of the passive upwelling of normal asthenospheric ond volcano. A basanitic to phonolitic intrusive com- mantle. Finally, there is no explanation why two roughly plex ( million years in age) is exposed on Selvagem parallel curved fracture zones would form and propagate Pequena belonging to the shield cycle of activity. Despite in the same curved direction and at the same average rate its small size, three magmatic stages have been identifi ed for at least  million years in this region. on Selvagem Grande: () a late Oligocene (occurring The hotspot or model, however, can – million years ago) tephritic to phonolitic shield adequately explain the parallel age progressions of old- cycle intrusive complex, () a Middle to Late Miocene est shield-cycle volcanism along curved southwest to (occurring – million years ago) mafi c alkaline late northeast paths for the Canary and Madeira volcanic cycle, and () a Pliocene (occurring . million years provinces. The age progressions of ∼ mm/year for both ago) mafi c alkaline late cycle. volcanic provinces are consistent with the rotation of the Seven large seamount complexes are located to the around a common Euler pole (at ° N, northeast of the Canary Islands. Many of the seamounts in ° W between  and  million years ago, and at ° N, the northeastern portion of the volcanic province are guyots ° W between  and  million years ago at an angular with fl at tops from which beach cobbles were obtained by velocity of ∼.° ± .°/million years) above relatively dredging, indicating that these guyots were former islands fi xed but distinct (based on differences in geochemistry that were eroded to sea level by wave action and then subse- for the two volcanic provinces) magmatic sources (i.e., quently subsided beneath sea level. Age-dated samples from mantle plumes). Strong additional support for the exis- four seamounts can be placed in shield and late cycles using tence of a mantle plume comes from seismic tomography, geochemical criteria (e.g., Pb isotopic composition). When which has imaged a mantle plume to the core–mantle only the oldest ages from the shield-stage volcanic rocks are boundary (at  km) beneath the Canary Islands. The considered, there is an age progression with ages increasing long history of volcanism on individual volcanoes could from southwest to northeast through the Canary volcanic result through small amounts of melting of plume mate- province, consistent with motion of the African plate in rial fl owing in the asthenosphere to the east and northeast this region over a relatively fi xed magma source at a rate of beneath the older volcanoes. ∼. mm/year over the last ∼ million years. SEE ALSO THE FOLLOWING ARTICLES

MODELS FOR THE ORIGIN OF THE CANARY Canary Islands, Biology / Eruptions / Seamounts, Geology VOLCANIC PROVINCE FURTHER READING A wide variety of models have been proposed to explain Carracedo, J. C. . The Canary Islands: an example of structural the origin of the Canary Islands and the Canary volcanic control on the growth of large oceanic-island volcanoes. Journal of province. These include volcanism resulting from decom- Volcanology and Geothermal Research : –. pression melting () along a leaky transform fault or prop- Carracedo, J. C., F. J. Pérez Torrado, E. Ancochea, J. Meco, F. Hernán, agating fracture (i.e., most likely an extension of the South C. R. Cubas, R. Casillas, E. Rodríguez Badiola, and A. Ahijado. . Cenozoic volcanism II: the Canary Islands, in The geology of Spain. Atlas fault system), () beneath rising lithospheric blocks W. Gibbons and T. Moreno, eds. London: Geological Society, –. as a result of tectonic shortening, () beneath a suture Carracedo, J. C., E. Rodríguez Badiola, H. Guillou, M. Paterne, zone running along the Atlantic margin of northwestern S. Scaillet, F. J. Pérez Torrado, R. Paris, and U. Fra-Paleo. . Erup- tive and structural history of Teide volcano and rift zones of Tenerife, Africa, or () of an upwelling mantle plume. The fi rst Canary Islands. GSA Bulletin : –. three sets of models rely upon structures that cut through Geldmacher, J., K. Hoernle, Pvd. Bogaard, S. Duggen, and R. Werner.   the lithosphere to cause and to control the location of the . New Ar/ Ar age and geochemical data from seamounts in the Canary and Madeira volcanic provinces: a contribution to the “Great volcanism, whereas the origin and location of volcanism Plume Debate.” Earth and Planetary Science Letters : –. in accordance with the fourth model is largely indepen- Guillou, H., J. C. Carracedo, F. Pérez Torrado, and E. Rodríguez Badiola. dent of the lithosphere. The curved northeast–southwest . K-Ar ages and magnetic stratigraphy of a hotspot-induced, fast alignment of the Canary and Madeira volcanic provinces grown oceanic island: El Hierro, Canary Islands: Journal of Volcanology and Geothermal Research : –. clearly deviates from the east–west orientation of fracture Hoernle, K., and H.-U. Schmincke. . The role of partial melting in zones in the East Atlantic crust. Furthermore, there is no the  Ma geochemical evolution of Gran Canaria: a blob model for the evidence for such faults in the Canary or Madeira volcanic . Journal of Petrology : –. Masson, D. G., A. B. Watts, M. J. R. Gee, R. Urgelés, N. C. Mitchell, provinces or for suture zones in these areas. In addition, T. P. Le Bas, and M. Canals. . Slope failures on the fl anks of the movements along structures cutting thick Mesozoic litho- western Canary Islands. Earth-Science Reviews : –.

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Gillespie08_C.indd 142 4/7/09 4:22:38 PM Paris, R., H. Guillou, J. C. Carracedo, and F. J. Pérez-Torrado. . Vol- canic and morphological evolution of La Gomera (Canary Islands), based on new K-Ar ages and magnetic stratigraphy: implications for oceanic island evolution. Geological Society [London] Journal : –. Schmincke, H. U. . Geological fi eld guide of Gran Canaria, th. ed. Kiel, Germany: Pluto-Press. Smith, W. H. F., and D. T. Sandwell. . Global seafl oor topogra- phy from satellite altimetry and ship depth soundings. Science : –.

CAPE VERDE ISLANDS

MARIA CRISTINA DUARTE AND MARIA MANUEL ROMEIRAS Instituto de Investigação Científi ca Tropical, ,

FIGURE 1 Cape Verde Islands: geographic location. Cape Verde’s natural heritage is unique. The physical environment of these islands creates a multiplicity of habitats with a great wealth of fauna and fl ora. Neverthe- Santiago is the largest island and is home to more than less, this biodiversity is naturally restricted to the narrow half of Cape Verde’s total population (, inhabitants geographical limits of the islands and is extremely vul- as of the  census), whereas the smallest island—Santa nerable to disturbances caused by human activities. The Luzia—is uninhabited. threatened island endemics are thus likely to benefi t from The northern and southern groups are characterized conservation management programs that are urgently by high mountains and offer a wide range of habitats in needed if Cape Verde’s natural levels of diversity are to relatively small areas. Slopes can be extraordinarily steep be maintained. (average gradients of ° to °), with active fl uvial ero- sion. The eastern group is composed of fl at islands, and PHYSICAL ENVIRONMENT such peaks as do exist reach only a few hundred meters and Geomorphology in height and are surrounded by relatively broad extents The Cape Verde archipelago is grouped together with of plain land, where deposition is dominant. Fogo Island the Azores, Madeira, the Selvagens, and the Canary contains Cape Verde’s tallest mountain—Pico do Fogo— Islands in the Macaronesian region, which is situated which rises to  m (Table ). in the North , close to the West African coast and the West Mediterranean region. The Cape TABLE 1 Verde archipelago consists of ten volcanic islands and Some Geophysical Features of the Cape Verde Islands several islets situated between °′–°′ N and °′–°′ W (Fig. ). It lies  km south of the Island Island Max. Population Group Names Area (km2) Altitude (m) (as of 2000) Canary Islands, and a mere  km separate Boavista Island from the African (the coast of ). Northern Santo Antão 779 1979 47,170  São Vicente 227 725 67,163 The archipelago is spread over , km of ocean and Santa Luzia 35 395 0 has about  km of coastline. São Nicolau 343 1304 13,661 The Cape Verde Islands are usually classifi ed in three Eastern Sal 216 406 14,816 groups: Northern Islands, Eastern Islands, and Southern Boavista 620 387 4209 Islands (Table ). However, other classifi cation groups are Maio 269 436 6754 also considered: the Windward Islands (Santo Antão, São Southern Santiago 991 1392 236,627 Vicente, Santa Luzia, São Nicolau, Sal, and Boavista), and Fogo 476 2829 37,421 Brava 64 976 6804 the Leeward Islands (Maio, Santiago, Fogo, and Brava).

CAPE VERDE ISLANDS 143

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