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ffiEI-SEVIER Journal of Volcanology and Geothermal Research94 (1999) I-I9 www.elsevier.com/locaIe / jv olgeorcs

Growth,structure, instability and collapse of Canarianvolcanoes andcomparisons with Hawaiianvolcanoes

JuanCarlos Carracedo . Estaci6nvotcanol6sica de Canarias(|PNA), Consejo CientiJicas(CSIO, 38206La Laguna,renerife, Y,,T;;:,rr:;:,r'rrrr::iones Received10 Mav 1999

Abstract

Recentonshore and offshoreinvestigations in the Canarianarchipelago, especially in the westernislands of and El Hieno, have greatly improved the understandingof the genesisand evolution of these islands and allow interesting comparisonswith other hotspot-inducedoceanic island volcanoes,especially the Hawaiian archipelago.Genesis induced by I hotspot activity and, consequently,shield and post-erosionalstages of growth allow the definition of similar main stratigraphicunits. The Canarianand Hawaiian volcanoesshow common constructionaland structuralfeatures, such as rift zones,progressive instability and multiple gravitationalcollapses. However, the Canariespresent some important geological differences from the prototypical hotspot volcanoes of the , particularly the absence of significantsubsidence; The Canarianvolcanoes remain emergentuntil completely mass-wastedby gravitationalcollapses and erosion.Volcanic formationsover 20 million years are observablein outcrop in the Canaries,including the seamount stagesof growth in severalof the islands.O 1999 Elsevier ScienceB.V. All rights reserved.

Keywords:; Hawaiian Islands; oceanic islands; comparative volcanism and structure

1. Introduction readily distinguishablehotspot signature (a clear hotspot trace, mantle anomaly and swell), generated Apart from the Hawaiian Islands,the Canariesare on a fast-movingplate (Wilson, 1963;Morgan,1972 probablyone of the most extensivelystudied groups Clagueand Dalrymple, 1987;Walker, 1990);and (2) of hotspot-generatedoceanic islands in the world. the Canaries, where the hotspot signature is geo- The comparison of the Hawaiian and Canarian chemically and geophysically less evident and the 'olcanoes leads to some interestins clarifications. plate velocity is lower by about an order of magni- h archipelago representsa distinctly characteris- tude (Filmer and Mcnutt, 1988; Hoernle and ic hotspot-inducedoceanic group: (1) the Hawaiian Schmincke, 1993; Canaset al., 1994; Watts, 1994). hipelago,the prototypical hotspot islands,with a There are several specific advantagesin the Ca- naries for the study of the processesand patterns of development, the structure, instability, and collapse of island volcanoes that are difficult to investigate ' E-mail: jcarracedo@ ipna.csic.es fully in other oceanic groups. Perhaps, the only

r1'l-0273/99/$ - seefront matter O 1999 Elsevier ScienceB.V. All riehts reserved. I: 503'17-0273 (99)00095-5 J.C. Carraceda / Journal ofVolcanology and Geotherrnal Research 94 (199q 1-19 similarly-advantaged group is the Cape Verde Is- islands of La Palma and and, to a lesser lands; unfortunately, the geology and geochronology extent, El Hierro (Carracedo,1994). of these remote islands are relatively little known. In this paper we review some important features The individual islands of the Hawaiian archipelago of the growth, structure, progressive instability and have a relatively short lifespan: high-rate subsidence flank collapse of the Canarian volcanoes and their (as quoted by Moore, 1987, most of the Hawaiian comparison with other oceanic volcanoes, especially volcaroes have subsided 2-4 kJ\ since emergence) those of the Hawaiian Islands. precludes the islands from continuing above sea level after only a few million years (Moore and Fornari, 1984; Moore, 1987; Moore and Thomas, 2. Growth of the Canarian volcanoes 1988; Walker, 1990). Kauai, the oldest emerged island in the Hawaiian chain, is less than 6 Ma 2.l. Geochronology and stratigraphy (McDougall, 1964, 19'79).Thus, only the relatively young parts of the islands are exposed to observa- The first comprehetsive stratigraphy of the Ca- tion. High rainfall gives rise to a dense vegetation naries was compiled by Ffster et al. (1968a,b,c,d)for screen and rapid weathering of rocks, making expo- the islands of Lanzarote. . Gran Ca- suresrelatively scarce.Thus, geological observations naria and Tenerife. Numbered stratigraphic series (I as well as radiometric dating and magnetic stratigra- to IV) were defined by the presence of a general phy are difficult in many areas, increasing the diffi- erosional unconformity and interbedded fossil culty of the complete reconstruction of these volca- beaches.Absolute dating of the volcanic formations noes (McDoryall, 1963, 1964, 1969, 1971, 1979; using radiometric (K/Ar) and palaeomagnetictech- McDougall and Tarling, 1963; McDougall and Ur- niques (Abdel-Monem et al., 1971,1972; McDougall Rahman, 1972; McDougall and Swanson, 1972;Hol- and Schmincke, 1976; Canacedo, 1979) made it comb, 1980; Naughton et al., 1980; Clague and clear that the stratigraphy defined was not applicable Dalrymple, 1987; Holcomb et al., 1997). to all the Canaries. In contrast, there is no comparable subsidencein The term "Series" used by Ffster et al. con- the Canaries, as discussed below. Volcanic forma- formed to the stratigraphic code in use at the time. tions over 20 Ma are observable in outcrop, includ- However, it does not conform to the present code ing the seamount stages of growth in several of the (NACSN, 1983), which restricts the use of this term islands, as discussedlater. Since all the Canaries are to geological units formed during the sametime-span. still emergent above sea level, it is feasible to study with synchronousboundaries. Recently impro in outcrop volcanic formations and structures over a geochronological (radiometric and palaeomagnet wide range of ages and original emplacementdepths, data reinforced these ideas (Ancochea et al., I according to the age of the islands and the different 1994:Guillou et al.. 1996.1998: Carracedo et al stagesof erosive mass-wasting.The vegetation cover 1999-this volume) suggesting to find a more is comparatively poor and the have a high K priate stratigraphic definition for the Canaries. content, favouring geochronological (K/Ar and Fig. 1 presentsa plot of the publishedK/ Ar palaeomagnetic reversals) determinations (Abdel- from flows of the Canarian and the Monem et al., L97I, 1972; McDougall and islands. When compared, we can easily see Schmincke, t976; Cartacedo, 1979; Ancochea et al., individual islands in both archipelagos show 1990, 1994, 1996; Coello et a1.,1992; Guillou et al., main stages of growth separatedby periods of 1996,1998; Caracedo et al., 1999-thisvolume). The canic repose (gaps). The combined use of pa high population and the absence of surface waters on magnetic reversalsand radiometric dating has the islands have necessitatedthe mining of ground- to be efficient in the Hawaiian Islands (Holcomb water by means of more than 3000 km of sub-hori- al.. 1997) and the Canaries (Abdel-Monem et zontal tunnels (locally known as "galerias"), which 1971,1972; Carracedo, 1979; Cnracedoand allow the observation of the internal structure of the 1995: P6rez Torrado et a1., 1995: Guillou et volcanoes at almost any point and depth in the 1996) in defining the presence of eruptive gaps E

J.C. Canacedo / Journal of Volcanology and Geothermnl Research 94 ( I99q I -19

d the Ca )fc Gran C& series(l d a generd fossil formatior EL HIERRO I.A GOMERA GRANCAMRIA LANZAROTE LA PALMA TENERIFE FUERTEVENTURA ic tecb A) made not appli 5.8 a Old shield-stage tl volcanisy___ ---1> tl et al. LJ at the present nse of this GAP satne tlme /\"-1 / et al., I I Carracedo et Shr€/d-stage I Islend a more t, Canaries n,J- I K/N i:; T - ""t""r-"rlr"r.rr, and the volca easily see HAWAII MAUI I-ANAI KAUAI NIIHAU ipelagos show Shield- -+ I by periods of stage Post-erosionalstage islands ined use of islands ric dating has B) Islands ( tMel-Monem et Fig. 1. Published K/Ar ages from lavas of the Canary Islands (A) and the Hawaiian Islands (B). The presence of a gap in the eruptive activity allows the separation in both archipelagos posterosional-stage brracedo and of two main stratigraphic units: Shield stage and volcanism. Hawaiian ages from (1987). (1971; (1976), et are Clague and Dalrymple Canarian ages are from Abdel-Monem et al. 1972), McDougall and Schmincke 995; Guillou Carracedo (1979), Ancochea et al. (1990,1994,1996), Coello et al. (1992), Guillou et al. (1996, 1998) and P6rez Torrado et al. (1995). of eruptive X-axis not to scale. I

I

4 J.C. Carracedo / Journal of VolcanoLog,-and Geothermal Research 94 ( I ggg) I - I g I (as hiatuses shown in Fig. 1) rather than sampling This feature was used in the Hawaiian Islands to f gaps. separatetwo main units (Fig. 2A) of generaluse in

I

I ost-erosional

I

Shield stage I

I

,u"] i I I1.1 I Post-s h ie ldt gap A)

|,:, j.., I

the archipe or post-el

Fig. 2. A mai island, which Shieldstage with a hotspo Gomera and I while in the F Tenerife) are Abdel-Monen I ( 1996).

I

I h* 94 ( 1999) I - I 9 J.C Carracedo / Journal of Volcanology and Geothermal Research

of the Canary lslands aiian Islands Sequentialsurfacing

56

Fig. 3. Sequential surfacing of the Canary Islands. Explanation in the text'

the archipelago:the shield stage and the reiuuenated 1987;Langenheim and Clague,1987; Walker, 1990). Canaries, or post-erosional stage (Clagve and DalrymPle, This division is easily applicable to the

of the oldest emerged volcanism in each Fig. 2. A main difference in the Canarian (A) and Hawaiian (B) archipelagos is related to the age islands, congnrent in both archipelagos istand, wtrlctr in the Canaries are considerably older. Note the progressive increase in the age of the Islands, where the islands of La with a hotspot model. This pattem is consistent in the Hawaiian chain but not completely in the Canary hotspot, as discussedin the text' Note that Gomera and Lanzarote lie in an anomalous position with respect to the general progression of the of the Canaries.(La Palma, El Hieno and while in the Hawaiian archipelago only the island of Hawaii is at present in the shield stage, three Dalrymple (1987). Canarian ages are from Tenerife) are at present in the same stage of development. Hawaiian ages are from Clague and (1990, et al. (1992) and Guillou et aI. Abdel-Monem ei al. (197 l), McDougall and Schmincke (1976), Ancochea et al. 1994, 1996), Coeilo (1996). J.C. Carracedo / Journal of Volcanology and Geothermal Research 94 ( 1999) I *19 which can be separatedaccordingly into three groups: Canaries, however, three islands spanning at least (1) ttre islands of Fuerteventura,Lanzarote and Gran 7.5 Ma are in the shield stageof growth (Fig. 2A). Canaria, at present in the post-erosional stage of development: (2) the island of La Gomera, in the repose (gap) stage, and (3) the islands of Tenerife, 2.2. Sequence of the emergence of the Canarian La Palma and El Hierro, in the shield stage of uolcanoes growth (P'ig. ZA). There are, however, two differences in the strati- The reconstruction of the sequenceof emergence graphic relationship of the Canaries as compared to above sea level of the Canaries(Fig. 3) also shows the Hawaiian archipelago. Firstly, a comparison of two interesting anomalies: (1) the emergence of La both archipelagosreveals significant differences: (a) Gomera prior to Tenerife (Figs. 3 and 4), in opposite in the age of the islands (Fuerteventura about four order to that expected from the westerly progression times older than Kauai); and (b) three islands in the of the hotspot; and (2) the simultaneous growth of Canarian archipelago are still in the shield stage, La Palma and El Hieno (Figs. 3-6). Although at whereas in the Hawaiian Islands only the volcanoes presentthis is highly speculative,there seemsto be a on the island of Hawaii are at present in this stage of correlation between periods of rapid growth in both growth. Another important difference between the islands in an "on-off" sequence,apparently linked Canarian and the Hawaiian volcanoes is the extinc- to the occurrence of catastrophic (Car- tion sequence(Stearns, 1946; Clague and Dalrymple, racedo et al., 1999-this volume). Precise geochemi- 1987): the main stage of growth of the Hawaiian cal investigations, especially isotopic, are required to Islands (usually lasting about 1 Ma according to clarify whether both islands have a common mag- Langenheim and Clague. 1987) was nearly com- matic source that can alternatively feed volcanoes in pleted before the next one emerged (Rig. Zn). tn ttre both islandsfollowins massivecollaoses.

k'(10 cmrU PaciJicPlate-Hawaiian E oohu fffirr ua"Xi wMo to kai

100 200 300 400 500km DISTANCE (from activeend of chain) I Fig. 5. (A) The C! Fig. 4. Oldest subaerial age vs. distance plot for the Canarian and Hawaiian islands. See text for explanation. Hawaiian ages are frorn cones (LTC in the I Ciague and Dalrymple (1987). Canarian ages are from Abdel-Monem et al. (1971), McDougall and Schmincke, 1976, Ancochea et al active in the Ha\d (1996). Q99O, 1994, 1996), Coello et al. 0992) and Guillou et al. ends the emerged I ;

94 ( 199q 1-19 J.C. Carracedo / Joumal of Volcanology and Geothermal Research

Fanning at least owth (Fig. 2A). rf the Canarian

pe of emergence g. also shows ffi*r 3) $) ir of La mergence 5(Fuefievertura rd 4), in opposite Ft o'o ferly progression )/7 .-,j neous growth of -6). Although at lt, ore seems to be a d growth in both apparently linked I,'A landslides (Car- hecise geochemi- b, are required to a common mag- feed volcanoes in lapses.

@ 500 km B) the qbundant litoral Fig. 5. (A) The Canaries have been very stable, at least in the last 15 Ma; subsidence is not significant, as shown by (Fb) pillow (Pw) located at about the present sea level. (B) Contrarily, subsidence is very Lwaiian ages are from coies (LTC in the frgure), fossil beaches and lavas reef terraces as shown in the figure (Moore, 1987). Subsidence finally 1976,Ancochea et al- active in the Hawaiian Islands, resulting in the presence of submerged , and late guyots' ends the emerged life of the island in a relatively short time span, probably less than about 6-7 Ma, changing to atolls I

J-C. carracedo / Journal ofvolcanology and Geothermal Research 94 ( I99q I-Ig

Ha po mt shi to

por col

g2l E*t ov( ma intt col 'ma ing ' nur mel ' witl onI al.. I Fig 6' Computer-generated3-D image (bathymety from of Hunrer er al., 1983) of the canary Islands viewed from the east. Note the int differences in the height of the islands, due in the canaries mainly to mass-wasting. ove Lan this Fig. 4 shows comparative plots of the oldest ages Lanzarote is imbricated with that of Fuerteventura, volr of subaerial volcanism vs. distance to the respective which may account for the observed dispersion. If ous younger end of the volcanic chains for the Canarian both groups (the islands at present in the shield stage Cor and the Hawaiian volcanoes. It is evident that the and those in the post-erosional stage) are plotted In tl Hawaiian volcanoes fit a line corresponding to an separately,they fit two different lines (dotted lines A ma) averagerate of propagation of volcanism of about 10 and B in the plot in Fig. 4), corresponding to differ- islar cm/a, similar to that of Clague and Dalrymple ent averagerates of propagation of about 2.0 and 3.j E (1987). Contrarily, the Canaries show a greaterdis- cm,/a, respectively. A similar trend is observable in stag persion. This dispersion is due to anomalies in the the Cape Verde Islands, where the northwestern than age-distance plot of the pairs La Gomera-Tenerife group of islands, from San Nicolau to Santo Antao, fore and Fuerteventura-Lanzarote, as discussed above, appears to define a separate,northwest directed age tens and may be a characteristic of hotspot-relatedisland trend, different from the general southward and west- asu groups on slow-moving plates. A similar anomaly ward trend in age of the archipelago (Stillman et al., ing occurs in the Cape Verde islands, a clear example of 1982;Mitchell et al., 1983). time hotspot-induced islands on a slow-moving plate year (Courtnay and White, 1986), where euaternary vol- 2.3. production rates and eruptiue inter canism frequency shiftedback from Brava to Fogo in a manner prod possibly analogousto the late Miocene switch from The Canariesand the Hawaiian volcanoes share a (P6rt La Gomera to Tenerife in the Canaries.The island of common trend of two-stage subaerial evolution. T Lanzarote is not an island sensustricto, but a prolon_ However, they differ greatly in the type of prob gation towards the NE of Fuerteventura: both islands involved and the rate in which they are produced and any ( are separatedby the La Bocaina straight, less than 50 supplied, much greater in the latter. This is clearly opm( m deep (see Fig. 6). The volcanic construction of reflected both in the much greater volumes of the stage ( (1999) J.C. Carracedo / Joumal ofVolcanology and Geothermal Research 94 1-19 t Hawaiian shields compared to the products of the and accurate K/ Ar ages,and with magnetic stratig- post-erosional magmatism in each island and in the raphy (Guillou et al., 1996), allow the closest possi- 1 much higher frequency of eruptions during the ble approach to the reconstruction of the entire 'l shield-building stage of each volcano (Holcomb, emerged volcanic history of any of the Canaries.The 1987). present emerged volume of the island, of about t Magma production rates may be difficult or im- 140-150 km3, has beenproduced in the last 1.2-1.5 possible to evaluate in the Canary Islands. The dis- Ma, giving an apparcnt average magma production continuous characterof volcanism, in which eruptive rate of 0.12-0.13 km3 7ka. However, rates increase gaps, inherent$ difficult to date, may predominate significantly if we take into consideration the three over periods of activity, make true evaluation of consecutive giant lateral collapses that affected the magma production rates unreliable unless large time island. each clearly exceeding100 km3. intervals are compared. Furthermore, giant lateral A similar evaluation of shield-stagemagma pro- collapses repeatedly remove large fractions of the duction rates in the presently post-erosional islands mass of an island, especially during the shield-build- is highly problematic. This is becauseit is impossi- ing stage and redistribute them over distances of ble to evaluate the volume removed by lateral col- hundreds or even thousands of kilometres. Several lapses (Stillman, 1999-this volume): it is difficult to megaturbiditesdeposited in the Madeira abyssalplain determine even the number of collapses in these within the past I Ma have been shown to have deeply-erodedislands, let alone the volumes of indi- originated in the Canarian Archipelago (Weaver et vidual collapses. aI.,1992). Eruptive frequency and volume vary considerably 2.4. Euolution of magmas in the Canaries,as observed in the historic eruptions rhe east. Note the over the last 500 years. The 1730-1736 eruption of The shield-stagevolcanism is characterisedin the Lanzarote is the largest to occur in the archipelago in Hawaiian Islands by tholeiitic basalts, with late this period by as much as an order of magnitude in minor volumes of alkali basalts and associateddif- Fuerteventura, volume (Carracedoet al., 1992). However, the previ- ferentiated magmas; during the rejuvenated stage, dispersion.If ous eruption of note in Lanzarote is that of Montafia silica-poor magmas (alkali basalts, basanites and the shield stage Corona, dated at 53 Ka (Guillou. unpublishedage). nephelinites) predominate (Langenheim and Clague, ) are plotted In the same period, as many as 100-1000 eruptions 1987). (dotted lines A may have taken place in the shield-building stage In the Canaries, no such contrast is evident and ing to differ- islands of El Hierro, La Palma and Tenerife. magma compositions are varied in both stages. The 2.0 and3.7 Eruption rates during the subaerial shield-building rocks of the shield volcanism are predominantly is observable in stage, which are 2 to 3 orders of magnitude greater basaltic (picrites, tholeiites and basanites) but with northwestern than those during the post-erosional stage, are there- associated differentiated lavas (phonolites and tra- to Santo Antao, fore implied by considering a period of the order of chytes). Highly differentiated felsic rocks occur in directed age tens of thousandsof years. But even this may not be large volumes in the shield-stagevolcanism of both ward and west- a sufficient averaging period because of the switch- Tenerife and Gran Canaria, and to a lesser extent in (Stillman et al.. ing of activity between shield-stage islands on the other islands. Post-erosionalrejuvenated volcan- timescales of the order of hundreds of thousandsof ism repeats a similar trend but with much smaller years and the occurrence of episodes of relatively volumes of rock involved in most cases,although the intense post-erosional volcanism cruptiue frequenq' such as that which Pliocene Roque Nublo stratovolcanoin Gran Canaria produced the Roque Nublo volcano on Gran Canaria (P6rez Tonado et al., 1995) representsperhaps the (P6rez I volcanoes share a Torrado et a1., 1995). most voluminous episode of post-erosional volcan- Saerial evolution. The eruptive history of the island of El Hierro is ism in any island in the world. Wide variations in E fype of magmas probably the best-constrainedgeochronologically of alkalinity occur in post-erosional stage volcanism, y are produced and any of the Canary Islands. The uncomplicated devel- sometimeswithin individual eruptions. The variation rr. This is clearly opment of the island, which is still in its juvenile from basanitesto alkali basalts seems to be a com- pr volumes of the stage of shield growth, together with the abundant mon feature in Holocene volcanic eruptions in the 10 J.C. Carracedo / Jounml of Volcanolog! and Geothermal Research 94 ( 1999) I I 9

Canariesbut exceptionaivariations from basanitesto ola, 1993; Meco et al., 1991). Even in the very rte alkali basaltsand tholeiitesin a single eruptionhave young island of La Palma, still in the early phaseof &Ilr been observedin the 1130-1136 eruprion of Lan- the shield-building stage, a beach shoreface sand in (Caffacedo zarote and RodriguezBadiola, 1991; Car- deposit of about 0.5 Ma old is to be found at El aIe racedo et a1., 1992). The latter is one of only two Time, close to presentsea level. Surtseyantuff rings un historic eruptions to have occurred in a post-ero- occur at present sea level in the coastlandsof the wi sional stageisland in the Canaries(the other is the majority of the Canaries(Fig. 5) as well as pillow sor small eruptionof 1824,also in Lanzarore). lavas of agesranging from the Miocene to present- res A similar lack of contrast between shield-stage day (Ibanola et a1.,1991; Carracedoand Rodriguez lQi and post-erosionalmagma compositionsmay also be Badiola,1993; Carracedo and Soler, 1995). atir evidentin otherisland groupson slow-movingplates. These observationsare clearly incompatiblewith bas In the Cape Verde islands,magma compositionsin the model proposed by Watts and Masson (1996) t\\ t all stages of activity are alkaline, and commonly that Tenerife has subsidedby at least 2.5 km during extremelyso. The only systematictrend identifiedby the iast 3-6 Ma. These authorsbase their model on "et (1989) Davies et al. was sparial: they found that some submarinefeatures they observedin the swath fior rocks in the northwesternislands (Sao Vicente-Santo bathymetry off the northern coast of Tenerife and stal Antao) were systematically more silica-under- they interpretedas subaerialgullies that subsequently obs saturatedthan those from the islands (Sal-Brava) subsidedto form submarinecanyons. An alternative tUfr which in their shield stage of activity were located explanationthat does not require subsidenceis that f€il\ above the inferred mantle plume head. The spatial these submarinecanyons form the underwatercon- Tor and temporal patternsof compositionalvariation in tinuationof subaerialbarrancos and havebeen carved con hotspot-relatedisland groups on slow-moving plates by submarineerosive processesrelated to the dis- glor may therefbre,in general,be more complex than in charge of the latter into the sea. Schmincke et al. of island groups on fast-movingplates such as the (1991)have come to the conclusion,after analysis of Iant HawaiianIslands. extensive land and marine data, that the island of l9e Gran Canaria has been remarkably stable with re- 2.5. Subsidencehistory spectto sealevel sinceabout 14 Ma. Theseauthors have identifiednearly horizontalseismic reflectors of 3.\ As already mentioned, all the Hawaiian islands Late Miocene to recent age that can be traced to subsideand will eventuallybecome seamounts. The northern Tenerife, an observationclearly in conflict -t.l amount, age and rate of subsidencehave been de- with the model proposedby Watts and Masson. rived from studiesof submarinecanyons, submerged Therefore, it appearsthat the islands of the Ca- R coral (see reefs and coastal terrace Fig. 5) of lava narian archipelago,located close to the African con- S\\'iiI deltas (Moore and Fornari, 1984; Moore, 1987; tinental margin, are extremely stableand has under- OCL-.1 Moore and Campbell,1987). gone neither subsidencenor uplift after emergence. ald. Evidence for the position of contemporary sea The lack of post-emergencesubsidence is in very 19t-- levels, in the form of marine abrasion platforms, strong contrastto the rapid subsidenceseen during pos\ littoral and beach sedimentarydeposits, coastal vol- the shield stage and later in the Hawaiian Islands aSn( canic depositssuch as hyaloclastite-basedlava deltas (Moore, 1987; Ludwig et al., 1991; Moore and ritt z and Surtseyantuff rings, and erosionalpalaeocliffs, Chadwick, 1995), but is also a f'eatureof the Cape an-elr is widespreadin the Canary Islands (Fig. 5). It also Verde archipelago(Stillman et al., 1982; Courtnay bl\ invariably occurs close to presentsea level, within and White, 1986). (i9; the range of eustaticsea level change.Marine abra- The lack of post-emergenceuplift, in contrastto _ge()n sion platforms up to several million years old and the major uplift implied by the occurence of rhe tion close to present-daysea ievel occur in the oldest Seamount formations, is also of interest since lr older islandsof Fuerteventuraand Lanzarote(Crofts, 1967; implies that prior to emergencelarge intrusive com- 0ctirr Lecointre et a1.,1961 ; Ffster et a1., 1968a.b:Meco plexes grew within the volcanoes,whilst post-emer- Ri and Stearns,1981; Canacedoand RodrisuezBadi- gence, endogenousgrowth of the edifices was lim- the C

-*.**-xr.,rrn-rm'mrrfi-Frr, nrnrttmH lf-fIf-TI J.C. Carracedo / Journal ofVolcanol.ogy and Geothermal Research 94 (1999 I-19 ll ited: this is consistent with the many geochemical galerias(Carracedo, 1994). A simplemodel explain- and petrologicaldata setsfor subaerialvolcanic suites ing the genesisof thesefeatures and their regular in the Canary Islands which indicate that these suites geometrywas proposedby Carracedo(1994), based are for the most part fed by magma reservoirs in the on previous mafhematicalwork carried out by Lu- underlying oceanic crust and/or oceanic lithosphere ongoet al. (1991).Triple fracturingin a symmetrical with only the more evolved suites of rocks showing patternwith anglesof 120"would be the least-effort some evidence for the presence of shallow magma responseto magma-inducedvertical upward loading. reseryoirs (Hasteen et al., 1997; Kluegel et al., 1997, As shownin Fig. 12B,these three-armed rifts at 120' 1999-this volume; Mangas et a1.,1997). The system- were also detectedusing Bouger gravity anomalies atic occurrence of this pattern implies an explanation in Tenerife(MacFarlane and Ridley, 1968)and La based on structural and mechanical differences be- Rdunion(Lesquer, 1990). Dyke swarmsare clearly tween subaerial and submarine volcanic edifices. in relation with the manifestly regular geometry of The computer-generatedimage in Fig. 6 shows an the three spectacularerosive cirques of Piton des "empty oceano' view of the Canarian archipelago Neigesin La R6union.Although difficult to observe, from the east. Differences in height of the shield dykes generally were oriented parallel to the main stage and post-erosional stage islands can be readily axesof the correspondingcirques. A possibleexpla- observed. However, this is not a constructional fea- nation for theseerosive cirques is by a processof ture, since Fuerteventura and Gran Canaria may have inversionof relief: erosionmay have preferentially reached similar or even greater elevations (P&ez affectedthe softerpyroclastic facies associated with Torrado et al., 1995; Stillman, 1999-this volume). In the concentrationsofvents alongthe rifts. Anisotropy contrast to the Hawaiian and other oceanic island due to the dyke-swarmsenhanced deepening of the groups, this is not a consequenceof subsidence,but gulchesand active collapsesat the steepwalls en- of mass-wasting through erosion and catashophic largedthem to becomethe presenterosive cirques. landsliding, as mentioned before (Carracedo et al., Apart from frequentlylosing their regulargeome- 1998, 1999-thisvolume; Stillman, 1999-thisvolume). try throughvolcano evolution, rift zonesare usually extensivelydismantled during the post-shield-stage gap and the post-erosionalstage due to the suscepti- 3. Main structural features of Canarian volcanoes bility of their pyroclasticrocks to erosion.As ob- servedin the HawaiianIslands, vents are no longer 3.1. Rifi zones associatedwith the pre-existingrift zonesduring the rejuvenatedstage (Langenheim and Clague, 1987) Rift zones that concentrate vdnts and dense dyke and this later stage of activity further covers and swarrns have been described in the majority of concealsthese structures.However. detailedstruc- oceanic volcanic islands (Wenfworth and Macdon- tural observationsmay help to identify the presence ald, 1953; MacDonald, 1972; Fiske and Jackson, of theserift zonesin other intraplate oceanicvolca- 1972; Walker, 1.992, 1999-this volume). They may noes. possibly be an invariable component of these islands, as noted by Walker (L992). Their typical three-armed rift zone geometry of oceanic island volcanoes, with 4. Instability and collapse of Canarian volcanoes angles of about l20o between them, was mentioned by Wennniorth and Macdonald (1953), MacDonald Islandvolcanoes grow to a greatheight. Consider- (1972) and Carracedo (1994). The original regular ing the edifice as a whole, they frequently rise geomety of rift zones is often lost during the evolu- severalkilometres from the oceanfloor. The westem tion of the volcano, especially if buttressed among Canariesrise from about6.5 kr (Bt Hieno) to about older volcanoes, as frequently happens in the very 8.5 km (Tenerife).Gravitational stresses and dyke active Hawaiian volcanoes (Fig. ZB). injections tend to progressivelyincrease the mechan- Rift zones can be observed in exceptional detail in ical instability of thesevolcanoes, especially in the the Canaries (Fig. 7A), by means of water tunnels or most activeshield-stage phases of growth. 12 J.C. Carracedo / Joumal ofVolcanology and Geothermal Research 94 (Iggq I_B

Fig. 7. Rift zonesare a conmon feature of the Canariesand the Hawaiian Islands. In the former, rifts show ,,Mercedes a regular Benz,, Fig. 8. Sir triple star configurationand are easily recognisedin the shield-stageislands. This geometry,mentioned in the Hawaiian rifts by Wentworth these tens and Macdonald(1953), is obscuredin theseislands probably by the active growthof the volcanoes. volcano. J.C. Carracedo / Journal of Volcanology and Geothermal Research 94 ( I99q I _ D

triple least-effoft fractures (120)

A) lnitialstage

Tensionalstresses in thetriple fracturesand increasino anisotropyallow preferEntial emplacementof dykesatthe Gravitationalstresses rifts. and instabilitvincrease as the volcaio grows

B) Development stage

Thesum ofthese "coherent" stresses eventuallyexceeds the stabilitv - threshold andtriggers a giantlandslide

Gravitationalstresses and instabilityinduced by votcanoovergrowth predominantat thisstage

C) Mature,unstable stage

Fig. 8. Simple model to illustrate the generation of different "coherent" stressesin overgrowth, unstable oceanic volcanoes. The sum of these tensional forces eventually exceeds the stability threshold and triggers a giant , restoring the stable configuration of the volcano. 14 J.C. Carracedo / Journnl of Volcanology and Geothennal Research 94 ( 1999 I - 19

The model proposed by Carracedo (1994) to ex- progressive mecharical instability and collapse of plain the genesisof rift zones is also relevant to the island volcanoes. In fact, both processes(develop-

LanzaaotF.-

4.5

1580 15? 1560 1550 1540

t G I I $ I t I rf , l:r '@tA

] 100kn , J.C. Carracedo / Joumal ofVolcanology and Geothermal Research 94 (199q 1-19 and collapse of ment of triple-armed rifts and progressiveinstability) 1999-this volume; Stillman, 1999-this volume) and Desses(develop- may be coupled, as depicted in the model in Fig. 8. offshore (Weaver et al., 1992; Masson and Watts, The development of triple-armed rifts promotes edi- 1995; Masson, 1996; Watts and Masson, 1996; fice overgrowth and steep, gravitationally unstable Canals et al., 1991) in the archipelago, showing at It flanks and concentrationsof dykes which destabilise least 12 identifiable giant collapses in the Canaries ? the flanks through magma overpressure during em- (Fig. 9A). Further investigations probably will result I placement (Swanson et al, 1976). These rifts induce in the recognition of many more of these structures, mechanical and thermal pressurisationof pore fluids especially on the southern flanks of the archipelago (Elsworth and Voight, 1995; Elsworth and Day, and in the eastern islands (Stillman, 1999-this vol- 1999-this volume), while the extensional stresses ume). These and similar collapses on the flanks of developed in the axial zones of the rifts by the flank Hawaiian volcanoes are frequently entirely subma- instability may reinforce the development of discrete rine (McMurtry et al., I999-this volume) and excep- rift zones tfuoughout the growth of the edifices. tionally they can abort, as did the San Andr6s rift These coherent stresseseventually exceed the stabil- flank collapse in El Hierro (Day et al.. 1997). ity threshold and trigger massive flank failures. The Collapse in oceanic volcanoes is not necessarily slide blocks consistently form between two branches catastrophic, as observed in the slow collapse of the of the rift system, with the remaining rift acting as a southern flank of Kilauea volcano (Swanson et al., buttress (Carracedo, 1994, l996a,b). 1976: Smith et al., 1999+his volume) on a Giant collapses were first recognised in the landward-dipping thrust fault system. This ongoing Hawaiian Islands (Moore, 1964; Moore et al., 1989). deformation is perhaps the best example of a slow Hawaiian landslides are among the largest on earth: collapse or slump on an oceanic island volcano. some of the individual debris avalanches are more Clague and Denlinger (I99a) consider that the driv- than 200 km in length and 5000 km3 in volume ing force behind this continuous deformation is the (Moore et al., 1989). GLORIA mapping shows that weight of a mass of dense,hot (and therefore plastic) debris avalanche deposits cover an area of about cumulates in the deeper parts of the highly active 100000 km2 around the Hawaiian archipelago (Fig. Kilauean rift zones. within the volcanic edifice. Sim- 9B). Similar recurrent large landslides have been ilar flank deformation does not appear to occur, at recognised in La R6union based on bathymetric least in inter-eruptive periods, in the Canarian volca- (L6nat et al., 1989), magnetic and gravity data noes: the edifices are essentially free of shallow (Rousset et al., 1989) and high resolution sonar seismicity between eruptions; there are no active, images (L6nat and Labazuy, 1990). growing fault scarps comparable to the Hawaiian In the Canaries, main tectonic processes,such as pali (Swanson et al., 1976); and, recent geodetic giant landslides, have been avoided until very re- monitoring of the Cumbre Vieja volcano on La cently to explain the genesis of the more prominent Palma (Mossopers. comm.) indicates the absenceof morphological escarpments(seacliffs, U-shaped val- flank deformation in the present inter-eruptive stage. leys and calderas) in the Canarian Archipelago. This contrast in styles of deformation may reflect the However, abundantevidence relating giant landslides absenceof shallow magma reservoirs or plastically- and straight-walled valleys, calderasand wide coastal deforming cumulate bodies within the Canarian vol- embayments has been found onshore (Carracedo, canic edifices during the subaerial shield stage of 1994, l996a,b; Day et al., 1997; Carracedo et al., growth.

Fig. 9. Giant landslides are a corrmon feature of oceanic islands and were frst recognised in the Hawaiian archipelago (B) by Moore (1964). In the Canaries (A), several giant landslides have been documented by on-shore and off-shore evidence in the shield-stageislands. However, this must be a cornmon feature in the juvenile stages of the remaining islands, where these landslides are more difiicult to identify (Stillman, 1999-this volume). Giant landslides in the Hawaiian Islands are from Moore et al. (1989). Giant landslides in the Canaries are from Masson and Watts (t99S), Watts and Masson (1996), Canacedo et al. (1999-this volume) and Stillman (1999+his volume). I I t6 J.C. Carracedo / Joumal ofVolcanology and Geothermal Research 94 (1999) I-19

5. Summary, discussion and conclusions These features and favourable observational char- acteristics (lack of thick vegetation cover, very good The Canary Islands have many important geologi- rock exposures, access to the internal structure of cal features in common with the Hawaiian Islands volcanoes by means of water tunnels) made the aad many other oceanic volcanic groups. The main Canaries an exceptionally advantageouslocation to stages of growth of the Canarian volcanoes, from obserye the structural feafures and the evolutionary which general stratigraphic divisions can be defined, stagesof oceanic volcanoes. are comparableto other oceanic groups of the world. The Canarian volcanoes also show common con- structional and structural features, such as rift zones, Acknowledgements progressive volcano instability and multiple gravita- tional collapses. However, the Canaries,as well as the Cape Verde Many of the ideas put forward in this work were clarified throughout'' islands, present some important geological differ- comparativediscussions'' dur- ing field ences from the prototypical hotspot volcanoes of the campaigns of the author in Molokai, Oahu Hawaiian Islands, possibly related to a comparatively and Kauai and in La Palma and El Hieno. Thorough low-activity hotspot and to a slow-moving plate. reviews by Paul Delaney and Mike Garcia led to The nature and evolution of magmas are quite substantialimprovement of this paper and are appre- different in both archipelagos: the main volcanic ciated. Discussions on the geological comparison of the Hawaiian edifices in the Hawaiian archipelago are constructed and the Canarian Islands with Robin Holcomb, by voluminous eruptions of tholeiitic basalts, while Bruce Nelson and Uri ten Brink during the 1996 in the post-shield stage alkalic basalts and differenti- dives with the Pisces V submersible of the University ates cover the main shield (MacDonald, 1972). In the of Hawaii off the north coast of Molokai were Canaries, silica-poor magmas (alkalic basalts and especially inspiring. Discussionsand comments by differentiates) form the bulk of the islands, tholeiitic colleagues attending the international workshop on oceanic (Sept. basalts being exceptional (Carracedo et al., 1992). islands 1997, La Palma, Canary Islands) Highly differentiated lavas (phonolites and trachytes) were especially valuable and are acknowl- occur in large volumes in the central Canaries(Ffster, edged. r97s). Lower eruptive rates and possibly cooler magmas in the Canariesthan in the Hawaiian Islands result in References higher aspect ratio volcanoes. Slopes are generally steeper in the early shields which progress towards Abdel-Monem,A., Watkins,N.D., Gasr, P.W., 1971. Potassium- unstable configurations. Catastrophic flank failures argon ages, volcanic snatigraphy, and geomagnetic polarity in the Canaries have shallower slide planes and history of the Canary Islands: Tenerife, La Palma, and Hierro. Am. J. Sci. 272,805-825. collapseshave lower mass volumes than those of the Abdel-Monem, A., Watkins, N.D., Gast, P.W., 1972. Porassium- Hawaiian volcanoes. argon ages, volcanic stratigraphy, and geomagnetic polarity Perhaps one of the most important characteristics history of the Canary Islands: Lanzarote, Fuerteventura, Gran of the Canaries is the lack of significant subsidence Canaria and La Gomera. Am. J. Sci. 272,490-521. at least over the last 15 Ma. This is relevant to Ancochea, E., Ffster, J.M., Ibarrola, 8., Cendrero, A., Coello, J.. Hem6n, F., Cantagrel, J.M., Jamond, explain why islands older than 20Ma are still emer- C., 1990. Volcanic evo- lution of the Island of Tenerife (Canary Islands) in the light of gent, while islands in the Hawaiian-Emperor vol- new K-Ar data. J. Volcanol. Geotherm. Res. 44, 231-249. canic chain submerge by subsidence after about 7 Ancochea, 8., Hemin, F., Cendrero, A., Cantagrel, J.M., Frister. Ma. A main characteristic of the Canaries is that J.M., Ibarrola, 8., Coello, J., 1994. Constructive and desrruc- their emergent phase will end after a very long time tive episodes in the building of a young oceanic island, La Palma, Canary Islands, and genesis of the Caldera compared to the HI, and only becauseof mass-wast- de Taburi- ente. J. Volcanol. Geotherm. Res. 60 (3-4), 243-262. ing processes (catastrophic in the early stages of Ancochea, 8., Brdndle, J.L., Cubas, C.R., Herndn, F., Huertas. development and erosion afterwards). M.J., 1996. Volcanic complexes in the eastem ridge of the J.C. Carracedo / Journal of Volcanology and Geothermal Research 94 ( 199il I -19 11

Canary Islands: the Miocene activity of the island of geoid acrossthe Cape Verde Rise: evidencefor dynamic Fuerteventura.J. Volcanol.Geotherm. Res.70, 183-204. support from a thermal plume in the mantle. Geophys.J. R. Canas,J.A., Pujades,L.G., Blanco,M.J., Soler, V., Carracedo, Astron.Soc. 87, 815-867. J.C., 1994. Coda-Q distribution in the Canary Islands. Crofts, R., 1967.Raised beaches and chronologyin north west -261. Tectonophysics246, 245 Fuerteventura.Canary Island Quatemaria9, 247-260. Canals,M., Alibes,B., Urgeles,R., Alonso,8., 1997.Landsliding Davies,G.R., Norry, M.J., Gerlach,D.C., Clifl R.A., 1989.A on the CanaryIslands. The missingsubmarine sediment record. combinedchemical and Pb-Sr-Nd isotopestudy of theAzores Internat.Workshop on ImmatureOceanic Islands, La Palma, and Cape Verde hotspots:the geodynamicimplications. In: Sepr,pp. 106-109. Saunders,A.D., Nony, M.J. (Eds.),Magmatism in the Ocean Carracedo,LC., 1979.Paleomagnetismo e historia volc6nica de Basins.Geol. Soc. London Spec. Publ., 42:23I-255. Tenerife.Aula de Cultura del Cabildo Insular de Tenerife, Day, S.J.,Carracedo, J.C., Guillou, H., 1997.Age and geometry Tenerife,Espafla, 82 pp. of an abortedrift flank collapse:the San Andr6s fault, El Carracedo,1.C., 1994.The CanaryIslands: An exampleof struc- Hieno,Canary Islands. Geol. Mag. 134(4),523-537. tural controlon the growthof largeoceanic-island volcanoes. Elsworth,D., Day, S.J., 1999.Flank collapsetriggered by intru- (3-4), b-ere J. Volcanol.Geotherm. Res. 60 225-24L sion: the Canarianand Cape Verde Archipelagoes.J. Vol- " dur- Carracedo,J.C., 1996.A simplemodel for the genesisof large canol.Geotherm. Res.94, 323-340. gravitational Oahu landslide hazardsin the Canary Islands. In: Elsworth,D., Voight, B., 1995,Dyke intrusionas a trigger for McGuire, (Eds.), Jones,Neuberg Volcano Instability on the large earthquakesand failure of volcanoflanks. J. Geophys. Earth andOther Planets. Geo1. Soc. London Spec. publ., 110: Res.100,6005-6024. led to 125-135. Filmer, P.E., Mcnutt, M.K., 1988. Geoid anomaliesover the Carracedo, aPPre- J.C., L996b.Morphological and structuralevolution of CanaryIslands group. Mar. Geophys.Res. 11, 77-g7. the westernCanary Islands: of hotspot-inducedthree-armed rifts Fiske, R.S., Jackson,8.D., 1972. Orientationand growth of or regionaltectonic Robin trends?J. Volcanol.Geotherm. Res. 72, Hawaiianvolcanic rifts: the effect of regionalstructure and 151-162. tl|e gravitationalstress. Proc. R. Soc. London,Ser. A 329,299-' Carracedo,J.C., Rodrlguez Badiola, E., 1991.Lanzarote: la erup- 320. of the ci6n volc6nicade 1730, with a colour, l/25.000 geological Ffster, J.M., 1975.Las Islas Canarias:un ejemplode evoluci6n Molokai map of the eruption.Editorial MAE, Madrid: l-1g4. espacial y temporal del vulcanismo oce6nico, Estudios Carracedo,J.C., Rodriguez Badiola, E., 1993.Evoluci6n eeol6eica Geol6gicos31, 439-463. y magm6ticade la isla de Lanzarote(Islas rro*shop CanariasiRevista Fdster,J.M., FerndndezSantin, S., Sagredo,J., 196ga.Geologia y de la AcademiaCanaria de Ciencias Canary 4,25-59. Volcanologiade lasIslas Canarias: Lanzarote. Instituto ,,Lucas Canacedo,J.C., Soler, V., 1995. Anomalouslyshallow palaeo_ Mallada", rknowl- C.S.LC.,Madrid. magneticinclinations and the questionof the age of the Ffster, J.M., Cendrero,A., Gastesi,p., Ibarrola,E., L6pezRuiz, CanarianArchipelago. Geophys. J. lnt. 122,393_406. J., 1968b.Geologia y Volcanologiade las Islas Cananas: Carracedo,J.C., RodriguezBadiola, E., Soler, V., 1992. The Fuerteventura.Instituto,,Lucas Mallada,,, C.S.LC., Madrid. 1730-1736 eruption of Lanzarote,Canary Islands:a long, pacheco, FristerJ.M., Herndndez A., Mufroz,M., RodrieuezBadi_ high-magnitude basaltic fissure eruption. J. Volcanol. ola, 8., GarciaCacho, L.. 1968c.Geotogia y Volca-nologia Geotherm.Res. 53 (t-4), 239_250. de las Islas Canarias:Gran Canaria.Instituto ,,Lucas Carracedo,J.C., Day, Mallada,,. S., Guillou, H., RodriguezBadiola, E., C.S.I.C.,Madrid. Canas,J.A., P6rezTonado, J.F., 199g. Hotspot Fcrsium- volcanism Ffster, J.M., Arafla, V., Brandle,J.L., Navarro, close to a passivecontinental J.M., Aparicio, rr poldrty margin: the Canary Islands. A., 1968d.Geologia y Volcanologia Geolog.Mag. 135(5), de las Islas Canarias: d Hidro. 591_604 Tenerife.Instituto ,,Lucas Canacedo, Mallada',,C.S.LC., Madrid. J.C., Day, S., Guillou, H., 1999. Giant p6rez euatemary Guillou, H., Carracedo,J.C., Torrado,F., RodriguezBadi_ landslidesin the evolutionof La palmaand El Hieno, Canary For.assium- ola, E., 1996. K-Ar ages and magneticstratigrlphy of Islands.J. Volcanol.Geotherm. Res.94, 169_190. a polarity hotspot-induced,fast grown oceanicisland: H Uieno, Canary Clague,D.A., Dalrymple,G.B., 1992. The Hawaiian_Emoeror Grr Islands.J. Volcanol.Geotherm. Res.73, volcanic chain. part I: 141_155. Geologicevolution. In: Decker, W., Guillou, H., p.H. Canacedo,J.C., Day, S.J., 199g.Dating the upper Wright, T.L., Stauffer (Eds.),yelsanirm in Hawaii, Coclb. i- U.S. Pleistocene-Holocenevolcanic activity of palrna Geol. SuweyProf. paper1350, La usingthe Yolcanic cro Vol l: 5_54. K-Ar technique. Clague,D.A., Denlinger, YTpiked J. Volcanol. Geotherm.Res. 86, b drc litttr d R.p., 1994.Role of olivine cumulatesin 137-r49. destabilizingthe flanks of Hawaiian 3r-l{9. volcanoes.Bull. Vol_ Hasteen,T.H., Kluegel, A., canol.56,425-434. Schmincke,H.U., 1997.Magmatic ,.\t.. F6s. underplating and Coello,J., crustal magma accumulation beneath the Cantagrel,J.M., Hem6n,F., Frister,J.M., Ibarrola,E.. rd dcsa|r- Canaryislands Archipelago as evidencedby fluid inclusions. Ancochea,E., Casquet,C., Jamond,C., Diaz De j.R., rsland- L, Terdn, Workshop on Volcanism and Volcanic Cendrero,A., 1992.Evolution Hazardsin Immature dc T.h; of the eastemvolcanic ridge of Intraplate Oceanic palma, the Canary Islands,La 1977: 26_27. a Islandsbased on new K_Ar data. J. Volcanol. Hoernle,K., Schmincke,H.U., 1993.The Geotherm.Res.53 (t_4), 251_274. role of partial metting F.. llsr,, in the 15-Mageochemical Courtnay,R.C., evolutionof Gran ianaria: a blob ribc of White, R.S., 19g6. Anomalousheat flow and - modelfor the Canarianhotspot. J. petrol. 34, 599_626.

I l8 LC. Carracedo / Joumal of Volcanology and Geothermnl Research 94 ( Iggq I _19

Holcomb, R.T., 1980. Kilauea volcano, Hawaii: chronology and MacDonald, G.A., 1972. Volcanoes. Prentice-Hall, Englewood morphology of the surficial lava flows. Tl. Department of Cliffs. NJ. Geology, Stanford University, USA. Masson, D.G., Watts, A., 1995. Slope failures and debris Holcomb, R.T., 1987. Volcanism in Hawaii. Eruptive history and avalanches on the flanks of volcanic oceanic islands: the Iong-term behaviour of Kilauea volcano. U.S. Geol. Surv. Canary Islands, off NW . Landslide News 9, 21-24. Prof. Pap. 1350, 261-350. Masson, D.G., 1996. Catastrophic collapse of the volcanic island Holcomb, R.T., Reiners, P.W., Nelson, 8.K., Sawyer, N.L.E., of Hierro 15 Kaago and the history of landslides in the Canary 1997. Isotopic evidence for two shield volcanoes exposed on Islands.Geology 24 (3),231-234. the island of Kaua'i, (9), Hawai'i. Geology 25 811-g14. McDougall, L, 1963. Potassium-argon ages from westem Oahu, Hunter, P.M., Searle, R.C., Laughton, A.S., 1983. Bathymetry of Hawaii. Nature 197, 344-345. the N.E. Atlantic, Sheet 5: Continental margin off N.W. McDougall, L, 1964. Potassium-argon ages from lavas of the Africa. Institute of Oceanographic Sciences, UK. Hawaiian Islands. Geol. Soc. Am. Bull. 75, 107-128. Ibanola, E., Frister, J.M., Ancochea, E., Hue(as, M.J., 1991. McDougall, L, 1969. Potassium-argon ages from lavas of Kohala Rocas volcrdnicas submarinas en la base de la Formaci6n Volcano, Hawaii. Geol. Soc. Am. Bull. 80, 2591*2600. Cafradas.Macizo de Tigaiga (N. de Tenerife). Geogaceta 9, McDougall, L, l9TL Volcanic island chains and sea floor spread- r7_20. ing. Nature 231, l4l-144. Kluegel, A., Hansteens, p.M.. T.H., Schmincke, H.U., Sachs, McDougall, 1., 1979. Age of shield-building volcanism of kauai 1997. Internat. Workshop on Immature Oceanic Islands, La and linear migration of volcanism in the Hawaiian Island Palma, Sept. 1997: 29-30. chain. Earth Planet. Sci. Lett. 46.31-42. Kluegel, A., Schmincke, H.U., White, J.D.L., Hoernle, K.A., McDougall, I., Schmincke, H.U., 1976. Geochronology of Gran 1999. Chronology and volcanology of the 1949 multi-vent Canaria, Canary Islands: age of shield building volcanism and rift-zone eruption on La Palma, Canary Islands. J. Volcanol. other magmaric phases.Bull. Volcanol. 40 (I), 57-77. Geotherm. Res. 94, 267-282. McDougall, I., Swanson, D.A., 1972. potassium-argon ages from Langenheim, V.A.M., Clague, D.A. 1987. The Hawaiian-Emperor lavas from the Hawi and Pololu Volcanic Series Kohala volcanic chain: Part IL Stratigraphic framework of volcanics Volcano, Hawaii. Geol. Soc. Am. Bull. 83, 3i3l-3738. rocks of the Hawaiian Islands. In: Decker, W., Wright, T.L., McDougall, I., Tarling, D.H., 1963. Daring of polariry zones in (Eds.), Stauffer, P.H. Volcanism in Hawaii. U.S. Geol. Surv. the Hawaiian Islands. Nature 200,54-56. Prof. Paper 1350-1: 55-84. McDougall, L, Ur-Rahman, A., I9i2. Age of the Gauss- Lecointre, G., Tinkler, K.J., Richards, H.G' 196i. The marine Matuyama boundary and the kaena and Mammoth events. quaternary of the Canary Islands. Acad. Natural Sci. philadel- Earth Planet.Sci. Lett. 14,367-390. phia 119(9,325-344. MacFarlane, D.J., Ridley, WJ., 1968. An interpretation of gravity L6nat, J.F., Labazuy, P., 1990. Submarine morphologies and data for Tenerife, Canary Islands. Earth planet. Sci. Lett. 4, structures of R6union. In: L6nat, J.F. (Eds.), Le Volcanism de 48 l -486. La R6union, Centre des Recherches Volcanol6giques, Cler- McMurtry, G.M., Henero-Bervera, E., Resig, J., Cremer, M.. mont-Ferrand. -7 France: 43 4. Smith, J.R., Sherman, C., Tonessan, M.8., 1999. Stratigraphic L6nat, J.F., Vincent, P., Bachblery, P., 1989. The off-shore conrrn- constraints on the timing and emplacement of the Alika z gianr uation of an active basaltivc volcano: Piton de La Fournaise Hawaiian submarine landslide. J. Volcanol. Geotherm. Res. (R6union Island, Indian Ocean): structural and geomorphologi- 94, 35-58. cal interpretation from Seabeam mapping. J. Volcanol. Meco, J., Stearns,C.E., 1981. Emergent littoral deposits in eastern Geotherm. Res. 36, 1-36. Canary Islands. Quat. Res. 15, 199-208. Lesquer, A., 1990. Deep structure of Reunion Island from gravity Meco, J., Petit-Mairte, N., Fontugne, M., Shimmield, G., Ramos. data. In: Lenat, (gAs.), J.F. Le volcanisme de La R6union. 4.J., 1997. The Quatemary deposits in Lanzarote and Centre des Recherches Volcanologiques, Clermont-Ferrand, Fuerteventura (Eastem Canary islands, ): an overvlew. France, In: Meco, J., Petit-Maire, N. (Eds.), Climates of the past. proc. Ludwig, K.R., Szabo, B.J., Moore, J.G., Simmons, K.R., 1991. CLIP Meet., Lanzarote and Fuerteventura. pub. Univ. Las Crustal subsidencerate off Hawaii determined from234IJ-2381J Palmas de Gran Canaria: 123-136. ages of drowned coral reefs. Geology 19, l7l-174. Mitchell, J.G., Le Bas, M.J., Zielonka, J., Furnes, H., 1983. On Luongo, petrazzuoli. G., Cubellis, E., Obizzo, F., S.M., 1991. A dating the magmatism of Maio, Cape Verde islands. Earth physical model for the origin of volcanism of the Tyrrhenian Planet. Sci. Lefi. 64, 61-76. margin: the case of the Neapolitan area. J. Volcanol. Geotherm. Moore, J.G., 1964. Giant submarine landslides on the Hawaiian Res.48, 173-185. Ridge. U.S. Geol. Surv. Prof. Pap. 501-D, 95-98. Mangas, J., Clocchiatti, R., P6rez Torrado, J.F., Massare, D., Moore, J.G., 1987. Subsidencein the Hawaiian Ridge. In: Decker. 1997. Peridotite xenoliths, olivine-pyroxene megacrysts and W., Wright, T.L., Stauffer, P.H. (Eds.), Volcanism in Hawaii. cumulates of the Bandama Volcanic Complex (Gran Canaria, U.S. Geol. Survey Prof. Paper 1350, Vol. l: 85-100. Spain): genesis in the oceanic lithosphere. Intemat. workshop Moore, J.G., Campbell, J.F., 1987. Age of tilred reefs Hawaii. J. on Immature Oceanic Islands, La Palma, Sept. 1997: 4I-43. Geophys. Res. 92, 2641-2646. J.C. Carracedo / Joumal of Volcanology and Geothermal Research 94 ( 1999 1-19 19

>[Iall, Englewood Moore, J.G., Chadwick, W.W., 1995. Offshore geology of Mauna Smith, J.R., Malahoff, A., Shor, A.N., 1999. Submarine geology Loaand adjacent areas, Hawaii. In: Rhodes, J.M., Lookwood, of the Hilina slump and morpho-structural evolution of Ki- lures and debris J.P. (Eds.), Mauna Loa Revealed: Structure, Composition, lauea volcano, Hawaii. J. Volcanol. Geotherm. Res. 94, 59-88. ranic islands: the History and Hazards. Am. Geophys. Union, Geophys. Mono- Stillman, C.J., Furnes, H., Le Bas, M.J., Robertson, A.H.F., l*ws 9,21-24. graph,92:21-44. Zielonka, J., 1982. The geological history of Maio, Cape lb volcanic island Moore, J.G., Fomari, D.J., 1984. Drowned reefs as indicators of Verde Islands. J. Geol. Soc. London 139, 34'1-361. lides in the Canary the rate of subsidence of the islands of Hawaii. I. Geol.92. Stillman, C.J., 1999. Giant Miocene landslides and the evolution 752-759. of Fuerteventura, Canary Islands. J. Volcanol. Geotherm. Res. m western Oahu, Moore, J.G., Thomas, D.M., 1988. Subsidence of Puna, Hawaii, 94,89-104. inferred from sulfur content of drilled lava flows. J. Volcanol. Swanson, D.A., Duffield, W.A., Fiske, R.S., 1976. Displacemenr from lavas of the Geotherm. Res. 35, 165-171. of the South flank of Kilauea Volcano: the result of forceful t07-t28. . Moore, J.G., Clague, D.A., Holcomb, R.T., Lipman, P.W., Nor- intrusion of magma in the rift zones. U.S. Geol. Surv. Prof. D lavas of Kohala mark, W.R., Torresan, M.E., 1989. Prodigious submarine Pap.963, 1-93. ,2597-2600. landslides on the Hawaiian ridge. J. Geophys. Res. 94 (812), Walker, G.P.L., 1990. Geology and volcanology of the Hawaiian d sea floor'spread- 17465-17484. Islands. Pacific Sci. 44,315-34'7. Morgan, W.J., 19'72. Deep mantle convection plume and plate Walker, G.P.L., 1992. Cohercnt intrusion complexes in large rolcanism of kauai motions. Bull. Am. Assoc. Petrol. Geol. 56, 203-312. basaltic volcanoes - a new structural model. J. Volcanol. r Hawaiian Island North American Comission on Stratigraphic Nomenclature, 1983. Geotherm. Res. 50, 4l-54. North American Stratigraphic Code. Am. Assoc. Petrol. Geol. Walker, G.P.L., 1999. Volcanic rift zones and thei intrusion Lonology of Gran BulI.67,841-875. swarns. J. Volcanol. Geotherm. Res. 94, 21-34. volcanism and bg Naughton, J.J., McDonald, G.A., Greenberg, V.A., 1980. Some Watts, A.B., gravity (D,5't-77. 1994. Crustal stmcture, anomalies and flex- additional potassium-argon ages of Hawaiian rocks: the Maui ure of the lithosphere in the vicinity of the Canary Islands. ages from ]argon volcanic complex of Molokai, Maui, Lanai and Kahoolawe. J. Geophys. J. Int. 119, 648-666. i Series Kohala Volcanol. Geotherm. Res. 7, 339-355. Watts, A.B., Masson, D.G., 1996. A giant landslide on the north ;t731-3738. P6rez Torrado, F.J., Carracedo, J.C., Mangas, J., 1995. flank of Tenerife, Canary Islands. J. Geophys. Res. in 100, t polarityzones Geochronology and stratigraphy of the Roque Nublo Cycle, 24487-24498. Gran Canaria, Canary Islands. J. Geol. Soc. 152, 807-818. Weaver, P.P.E., Rothwell, R.G., Ebbing, J., Gunn, D.E., Hunter, of the Gauss- Rousset, D., Lesquer, A., Bonneville, A., L6nat, J.F., 1989. P.M., 1992. Correlation, frequency of emplacement and source Complete gravity study of piton de La Fournaise volcano, directions of megaturbidites on the Madeira Abyssal Plain. R6union Island. J. Volcanol. Geotherm. Res. 36, 37-52. Mar. Geol. 109, l-20. of gravity Schmincke, H.U., Sumita, M., Funck, T' 1997. Growth and Wentworth, C.K., Macdonald, G.A., 1953. Structures and forms Sci. Lett. 4, destruction of Gran Canaria: Evidence from land studies. of basaltic rocks in Hawaii. U.S. Geol. Surv. Bull. 994, 98. bathymetry, offshore seismic studies and drilling during ODP Wilson, J.T., 1963. A possible origin of the Hawaiian Islands. Cremer,M.. J., Leg 157. Internat. workshop on Immature Oceanic Islands, La Can. J. Phvs. 41.863-870. D9. Stratigraphic Palma, Sept. 1997: lL-12. 6e Alika z giant Creotherm. Res

ln eastern

G., Ramos. L:nzarote and an overvlew. the Past. Proc. Univ. Las

H.. 1983.On blands. Eanh

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. In: Decker in Hawaii. r00.