Geology of the Canary Islands

The geology of the Canary Islands is dominated by volcanoes and volcanic rock. The Canary Islands are a 450 km-long (280 mi), east-west aligned archipelago of volcanic islands in the North Atlantic Ocean, 100–500 km (60–310 mi) off the coast of Northwest Africa.^[1] The islands are located on the African tectonic plate. The Canary Islands are an example of intraplate volcanism because they are located far (more than 600 km (370 mi)) from the edges of the African Plate.^[2]

From east to west, the main islands are Lanzarote, Fuerteventura, Gran Canaria, Tenerife, La Gomera, La Palma, and El Hierro.^{[Note 1]} There are also some minor islands and islets: La Graciosa, Lobos, and the Chinijo Archipelago (Alegranza, Montaña Clara, Roque del Este and Roque del Oeste). The seven main Canary Islands originated as submarine seamount volcanoes on the ocean floor, which is 1,000–4,000 m (3,000–13,000 ft) deep in the Canarian region.

Lanzarote and Fuerteventura are separated by an 11 km-wide (7 mi), 40 m-deep (130 ft) ocean strait. Both islands are parts of a volcanic ridge called the Canary Ridge. These two islands have sometimes been a single island in the past when worldwide sea level was lower than its present level.^[4]

The Canary Islands, and some seamounts to the north-east, form the Canary Volcanic Province. The current long period of volcanic activity in this province started about 70 million years ago.^[5] For the first 50 million years, all the volcanic eruptions in the province occurred on the ocean floor but since 20 million years ago, enough lava has accumulated on the ocean floor at several particular locations in the province to form each of the islands in turn.

Volcanic activity has occurred during the Holocene Epoch (the last 11,700 years) on all of the main islands except La Gomera.^[6] The Canary Islands region is still volcanically active. The most recent volcanic eruption on land occurred in 2021^[7] and the most recent underwater eruption was in 2011-12.^[5]

Volcanic activity in the Canary Volcanic Province started about 70 Ma (million years ago), occurring at numerous seamounts and the Savage Islands, across an area of the ocean floor up to 400 km (250 mi) north of the Canary Islands. The northernmost of this group of seamounts, Lars seamount (about 380 km (240 mi) north of Lanzarote), has been dated to 68 Ma. The seamounts are progressively younger southwestwards towards Lanzarote.^[8]

The Canary Islands are built upon one of the oldest regions of Earth's oceanic crust (175–147 Ma), part of the slow-moving African Plate, in the continental rise section of northwest Africa's passive continental margin.^[9][10] The oceanic lithosphere is about 60 km (40 mi) thick at the central Canary Islands and about 100 km (60 mi) thick at the western islands.^[11]

Two seamounts, Las Hijas (southwest of El Hierro) and El Hijo de Tenerife (about 200,000 years old, located between Gran Canaria and Tenerife) may eventually (in the next 500,000 years) form new islands by future eruptions adding more lava flows to their volcanic edifices.^[12]

Volcanic oceanic islands, such as the Canary Islands, form in deep parts of the oceans. This type of island forms by a sequence of development stages:^[13]

1. submarine (seamount) stage
2. shield-building stage
3. declining stage (La Palma and El Hierro)
4. erosion stage (La Gomera)
5. rejuvenation/post-erosional stage (Fuerteventura, Lanzarote, Gran Canaria and Tenerife).^[13]

The Canary Islands differ from some other volcanic oceanic islands, such as the Hawaiian Islands: for example, the Canary Islands have stratovolcanoes, compression structures and a lack of significant subsidence.^[13]

The seven main Canary Islands originated as separate submarine seamount volcanoes on the floor of the Atlantic Ocean (although the distance between Lanzarote and Fuerteventura was small enough for their seamounts to overlap as they grew; the distance between Tenerife and La Gomera was also small enough for their seamounts to overlap as they grew). Each seamount, built up by the eruption of many lava flows, eventually became an island. Subaerial volcanic eruptions continued on each island. Late-stage fissure eruptions dominated on Lanzarote and Fuerteventura, resulting in relatively subdued topography with heights below 1,000 m (3,300 ft). The other islands are much more rugged and mountainous. The volcanic edifice of Tenerife, which is capped by Teide stratovolcano, rises about 7,500 m (24,600 ft) above the ocean floor (about 3,780 m (12,400 ft) underwater and 3,715 m (12,188 ft) above sea level);^{[Note 2]} measured from the ocean floor, it is the tallest volcanic edifice on Earth, except for a few in Hawaii.^[15][16][17]

The volume of volcanic rock that has built up the Canary Islands to thousands of metres above the ocean floor is about 124,600 km³ (29,900 cu mi); 96% of this lava is hidden below sea level and only 4% (4,940 km³ (1,190 cu mi)) is above sea level.^[18] The western islands have more of their volume (7%) above sea level than do the eastern islands (2%).^[18]

From about 70 Ma to about 20 Ma, all the volcanic activity in the Canary Islands region occurred as underwater eruptions and the islands did not yet exist. Eventually, enough lava accumulated at particular locations to form each island of the Canary Islands archipelago. The age of the first underwater eruptions differs from island to island; for example, the first underwater eruptions at La Gomera were at more than 12 Ma but at La Palma they were at 4 Ma. Seamount stage rocks are not exposed on Lanzarote, Tenerife, Gran Canaria and El Hierro, which has prevented dating of the earliest underwater volcanic activity at these islands.

The age of the oldest subaerially-erupted lavas on each island decreases from east to west along the island chain: Lanzarote-Fuerteventura (20.2 Ma), Gran Canaria (14.6 Ma), Tenerife (11.9 Ma), La Gomera (9.4 Ma), La Palma (1.7 Ma) and El Hierro (1.1 Ma).^[19][2]

Volcanic rock types found on the Canary Islands are typical of oceanic islands. The volcanic rocks include alkali basalts, basanites, phonolites, trachytes, nephelinites, trachyandesites, tephrites and rhyolites.^[13][6]

Outcrops of plutonic rocks (for example, syenites, gabbros and pyroxenites) that formed deep below the surface occur on Fuerteventura,^[20] La Gomera and La Palma. Apart from some islands of Cape Verde (another volcanic island group in the Atlantic Ocean, about 1,400 km (900 mi) south-west of the Canary Islands), Fuerteventura is the only oceanic island known to have outcrops of carbonatite.^[21]

Examples of the following types of volcanic landforms occur in the Canary Islands: shield volcano, stratovolcano, collapse caldera, erosion caldera, cinder cone, coulee, tuff cone, tuff ring, maar, lava flow, lava flow field, dyke, volcanic plug.^[24]

Several hypotheses have been proposed to explain the volcanism of the Canary Islands.^[25] Two hypotheses have received the most attention from geologists:^[26]

1. The volcanism is related to crustal fractures extending from the Atlas Mountains of Morocco.
2. The volcanism is caused by the African Plate moving slowly over a hotspot in the Earth's mantle.

Currently, a hotspot (the Canary hotspot) is the explanation accepted by most geologists who study the Canary Islands.^[27][28]

Evidence in favour of a hotspot origin for Canarian volcanism includes the age progression in the arcuate Canary Volcanic Province occurring in the same direction and at the same rate as in the neighbouring arcuate Madeira Volcanic Province (about 450 km (280 mi) farther north). This is consistent with the African Plate rotating anticlockwise at about 12 mm (0.47 in) per year.^[29] Also, seismic tomography has revealed the existence of a region of hot rock extending from the surface, down through the oceanic lithosphere to a depth of at least 1,000 km (620 mi) in the upper mantle.^[30]

Seventy-five confirmed volcanic eruptions have occurred in the Canary Islands in the Holocene Epoch (the last 11,700 years of Earth's geological history).^[31] Sixteen of these eruptions have been during the Modern Era of European history (that is, after c.1480, which corresponds closely to the final stages of the Spanish conquest of the Canary Islands; therefore, these eruptions are also known as historical eruptions because Spanish written eyewitness reports exist).^[31] In the last 500 years, volcanic eruptions have occurred, on average, every 30 to 35 years.^[32] However, in the Modern Era, the repose period between infrequent eruptions at each island has been highly variable (for example, 26 to 237 years for La Palma; 1 to 212 years for Tenerife), making reliable prediction of future eruptions unlikely.^[33][31]

Volcanic eruptions in the Canary Islands

Island	Holocene (last 11,700 years)	Modern Era (since c. 1480)	Modern Era eruption dates	Notes	Ref.
Lanzarote	4	2	1730–1736, 1824		[34]
Fuerteventura	0	0	——	No specific confirmed Holocene eruptions, but they are inferred to have occurred (based on the freshness of some lavas and some volcanic landforms)	[35]
Gran Canaria	11	0	——		[36]
Tenerife	42	5	1492, 1704–1705, 1706, 1798, 1909		[37]
La Gomera	0	0	——		[32]
La Palma	14	8	1481(±11), 1585, 1646, 1677–1678, 1712, 1949, 1971, 2021		[38]
El Hierro	4	1	2011–2012		[39]

Volcanic activity at Lanzarote started during the Oligocene Epoch at 28 Ma.^[40] For about the first 12 million years, the lava pile of a submarine seamount built up from the 2,500 m-deep (8,200 ft) ocean floor.^[41] Then, in the Miocene Epoch, from 15.6 Ma to 12 Ma, the Los Ajaches subaerial shield volcano grew as an island on top of the seamount, in an area corresponding to present-day southern Lanzarote.^[42] Between 10.2 Ma and 3.8 Ma, volcanic activity was focussed about 35 km (22 mi) to the northeast, forming a second shield volcanic island called Famara.^[43] Between Los Ajaches and Famara volcanoes, a central volcanic edifice was also active from 6.6 to 6.1 Ma.^[44] The edifices gradually merged to form a single island, Lanzarote, at about 4 Ma.^[45] From 3.9 Ma to 2.7 Ma, volcanic activity paused and the island was eroded.^[46] Today, although the lavas of Los Ajaches volcano are now mostly covered by calcrete,^[47] the eroded remains of the two shield volcanoes are preserved in southern and northern Lanzarote respectively, with small outcrops of the central edifice occurring between them. At about 2.7 Ma, in the late Pliocene Epoch, the rejuvenation stage began. It produced much less lava than the earlier shield stage, mainly at the Montaña Roja and Montaña Bermeja volcanoes in southern Lanzarote.^[46] Then, throughout the subsequent Pleistocene and Holocene epochs, the rejuvenation volcanism has continued and has been dominated by strombolian-style eruptions of lava from sets of volcanic cones aligned along numerous NE-SW fissures in the central part of Lanzarote.^[48] Geologically recent examples of rejuvenation stage volcanism include eruptions at Montaña Corona (about 21,000 years ago), Timanfaya (1730–1736) and Tao/Nuevo del Fuego/Tinguatón (1824).^[49][50][51]

The Timanfaya eruption (1730–1736) erupted more than one billion cubic metres (1 km³ (0.24 cu mi)) of lava, and a large volume of pyroclastic tephra, from more than 30 volcanic vents along a 14 km-long (9 mi) fissure in western Lanzarote. The lava flows cover one quarter of the island (an area of about 225 km² (87 sq mi)) with some of the flows reaching about 50 m (160 ft) in thickness. It is the largest Modern Era eruption in the Canary Islands, and the third largest eruption of basaltic lava on Earth in historical times.^{[52][53][54][55][56]}

Almost all the volcanic rocks of Lanzarote are basaltic.^[57]

Fuerteventura is situated on Mesozoic oceanic crust, about 70 km (40 mi) from the edge of the African continental shelf and about 100 km (60 mi) from the African mainland, making it the Canarian island closest to Africa.

Due to its old age, the oceanic crust at Fuerteventura is relatively rigid and this has prevented subsidence and allowed weathering and erosion to expose deep levels of the island's geological structure.^[58]

The two main rock sequences of Fuerteventura are (1) a lower, older (Cretaceous to early Miocene) sequence of sedimentary, plutonic and submarine seamount volcanic rocks with intrusive dykes, often called the "Basal Complex", which is unconformably overlain by (2) a younger sequence of Miocene, Pliocene and Quaternary subaerial volcanic rocks.

The oldest rocks of Fuerteventura are a set of mafic plutonic rocks, marine sedimentary rocks and volcanic rocks, which are intruded by igneous dykes.^[59] The sedimentary rocks of the Basal Complex were deposited on the ocean floor and represent the uppermost part of the oceanic crust that was uplifted and incorporated into the volcanic edifice during volcanic activity. The Mesozoic sedimentary rocks are mostly metamorphosed, and they are steeply tilted. The tilting occurred in the mid-Cretaceous and was probably caused by the uplift of Africa.^[60][61] Fuerteventura's first alkaline magmatism intruded plutonic rocks into the oceanic crust at about 70 Ma.^[13] This signifies a change to a hotspot environment. A submarine seamount started to form on the ocean floor during the Eocene Epoch, at about 39 Ma.^[13] The igneous rocks of the Basal Complex probably represent the seamount stage of Fuerteventura’s volcanic history, exposed due to uplift and erosion.^[62]

In the early Miocene, volcanic activity transitioned from submarine to subaerial while the volcanic edifice was gradually built up above sea level. Fuerteventura has the oldest subaerial volcanic rocks of the Canary Islands, which have been dated to 20.6 Ma.^[63] There were three main shield volcanoes built on the seamount base (from north to south): the Northern Edifice, the Central Edifice and the Jandia Edifice.^[64][65] The central shield volcano is the oldest, built mostly from 22 to 18 Ma but with a later phase from 17.5 to 13 Ma. The southern shield volcano formed from 21 to 14 Ma. The northern shield volcano was built mainly from 17 to 12 Ma.^[66] These shield volcanoes erupted mostly basaltic and trachybasaltic lava flows.^[67]

In the late Miocene (from about 11.5 Ma), there was a pause in volcanic activity (the erosional stage). Minor volcanic eruptions resumed in the Pliocene, at about 5.1 Ma (the rejuvenation stage) and they continued sporadically into the Quaternary, with basaltic lava flows dominating again.^[68]

The most recent volcanic eruption on Fuerteventura that has been dated occurred 134,000 years ago in the middle Pleistocene.^[69] Some undated volcanic cones in northern Fuerteventura may have formed more recently.^[70]

Weathering, erosion and sedimentation during the Pliocene and Quaternary formed coastal and shallow-sea sedimentary rocks that were eventually covered by younger aeolian sediments, alluvial fan deposits and palaeosols.^[71]

After early Miocene submarine volcanic eruptions created a seamount, subaerial volcanic activity at Gran Canaria occurred in three phases: shield stage (middle- and late-Miocene, 14.5 to 8.5 Ma), erosional stage (late Miocene, 8.5 to 5.3 Ma) and rejuvenated stage (Pliocene to Quaternary, 5.3 Ma to present).^[72]

The shield stage started with an early phase of eruptions of basaltic lava flows, from 14.5 to 14.1 Ma, which built the main subaerial shield volcanic edifice that forms three quarters of the subaerial volume of Gran Canaria.^[73] At least three shield volcanoes were active during this stage of island development and their lava flows gradually merged together into a single large landform.^[74] This was followed by a later phase, from 14.1 to 8.5 Ma, of explosive volcanic eruptions of differentiated felsic lavas (phonolites, trachytes and rhyolites) with many pyroclastic flows (that deposited ignimbrites). In central Gran Canaria, Tejeda caldera and a cone sheet swarm were formed in this phase.^[75]

From 8.5 to 5.3 Ma, in the erosional stage, there was minimal volcanic activity. Erosion occurred along with deposition of alluvial sediments on the island and deposition of submarine turbidite sediments offshore.^[76]

In the rejuvenation stage, from 5.3 Ma to present, volcanic activity has occurred in three phases. The first phase, from 5.3 to 2.7 Ma, was dominated by the formation of Roque Nublo stratovolcano in the central part of Gran Canaria. This produced lava flows, ignimbrites and debris avalanche deposits.^[77] The second phase (3.5 to 1.5 Ma) had strombolian-style effusive eruptions of lava flows along a northwest-southeast trending volcanic rift.^[78] The current phase, from 1.3 Ma to the present, has featured scattered phreatomagmatic and strombolian eruptions of very alkaline lavas.^[79] The most recent volcanic eruption on Gran Canaria occurred about 2,000 years ago at Bandama crater, in the northeast part of the island.^[80][81]

Sand dunes, with a total volume of 18 million cubic metres (24×10^⁶ cu yd), cover an area of 3.6 km² (1.4 sq mi) of the Maspalomas cuspate foreland on Gran Canaria's south coast.^[82] Aeolian landforms found in this dune field include barchan dunes and dune ridges (transverse dunes). The dunes are made of sand grains and pebbles. The average thickness of the dunes is 5–10 m (16–33 ft) but some dunes reach 20 m (66 ft) thick.^[83] In a few areas, the underlying deltaic sediments are exposed.^[84] The sand that has built the dunes has been moved about 2 or 3 km (1 or 2 mi) by water waves and wind from the sediment source area (an offshore submarine shelf at Playa del Inglés). Since the 1960s, urbanisation has affected the local winds and this has caused the gradual reduction in volume and area of the dune field because sediment erosion now exceeds sediment deposition.^[85] The dunes had long been thought to have formed during the last several thousand years^[86] but a 2021 study found evidence supporting a hypothesis that the dunes formed less than 300 years ago, as a consequence of a tsunami generated by the 1755 Lisbon earthquake.^[87][88]

Tenerife's subaerial shield stage of island development started at about 11.9 Ma in the late Miocene Epoch.^[89] First, a shield volcano called Tenerife central shield volcano grew as an island at what is now the central part of Tenerife. This central shield volcano was active from 11.9 to 8.9 Ma.^[90] Most of this central shield volcano's lavas have been covered by younger lavas from younger volcanoes; some small patches of the central shield volcano's lavas are now preserved as the Roque del Conde massif in the centre of the island. Then, in northwestern Tenerife, a second shield volcano (Teno shield volcano) formed from 6.4 to 5.1 Ma; its remains are the Teno massif.^[91] Then, from 4.9 to 3.9 Ma, a third shield volcano (Anaga shield volcano) was active in the northeastern part of Tenerife; the remains of this volcano are the Anaga massif.^[92] The lavas of these three shield volcanoes gradually formed a combined volcanic edifice that accounts for 90% of Tenerife's current volume.^[93]

The rejuvenation stage of Tenerife (after a long erosive gap in activity at the centre of Tenerife) started at about 4 Ma and continues to the present day. Between 4.0 and 0.2 Ma, a large stratovolcano (Las Cañadas volcano) formed, centred in the central part of Tenerife. Las Cañadas volcano covered some parts of the three older shield volcanoes.^[94] This volcanic activity at the centre of Tenerife has included cycles of basaltic lavas (e.g. basanites and tephrites) alternating with significant amounts of magmatically differentiated (more felsic and more alkaline) lavas (e.g. tephri-phonolites and phonolites).^[95] Central volcanic activity has been accompanied, since 3 Ma, by mostly basaltic fissure eruptions at a three-armed Y-shaped radial rift zone system that has northwest, northeast and south rift zones.^[96] About 200,000 years ago, Las Cañadas volcano collapsed, forming Las Cañadas caldera. In this 16 km × 20 km (9.9 mi × 12.4 mi) caldera, two related stratovolcanoes have formed: Teide (most of its eruptions occurring before 30,000 years ago) and its younger, smaller, western, close neighbour Pico Viejo (most of its eruptions occurring between 27,000 and 14,600 years ago).^[97] Both of these stratovolcanoes are still active. Together with some satellite vents, they form the Teide-Pico Viejo Volcanic Complex.^{[98][99][a][b]} Most of Tenerife's Holocene eruptions have occurred at the radial rift zones rather than at the two stratovolcanoes.

During the Holocene Epoch, Tenerife has had 42 confirmed volcanic eruptions, which is more than any other Canary island.^[100] Tenerife is currently at the point in its geological development where the effects of constructive volcanic eruption and destructive erosion are roughly balanced.^[101]

The seamount base (also known as the Submarine Edifice) of La Gomera was built by volcanic eruptions during the Miocene Epoch. The precise age range of this submarine volcanic activity is uncertain. Dating done in the early 1970s suggested that submarine volcanic eruptions occurred from 20 Ma to 15 Ma, followed by an erosion gap of 5 million years. The reliability of these dates has been questioned; dating done in the 2000s suggests that submarine volcanic eruptions began instead at about 12 Ma.^[102][103] At the end of the seamount stage, the seamount's top surface was eroded.^[104][105] There are a few small areas of old lava flows that some geologists claim represent an upper part of the submarine seamount (a "Basal Complex" similar to those found on some of the other Canarian islands) but this is disputed; an alternative explanation is that the lavas in question instead represent early subaerial shield volcano eruption material that flowed off the island into the ocean.^[106]

In the late Miocene, at about 11 Ma, La Gomera's shield-building stage began.^[108] The oldest subaerially-erupted lavas on La Gomera have been dated to 9.4 Ma.^[109] Most of the subaerial shield volcano's growth occurred from 9.4 to 8.0 Ma.^[110] The shield volcano lavas are also known as the Old Edifice.^[111] About 8 Ma, the northern part of the mafic alkaline shield volcano collapsed (the Garajonay landslide).^[112]

From 7.5 Ma to 6.5 Ma, the Vallehermoso stratovolcano grew on top of the partially collapsed shield volcano by eruption of relatively felsic lavas (phonolites and trachytes) which covered much of the older shield volcano.^{[113][114][115]}

In the early Pliocene, from 5.5 Ma to 4.2 Ma, basaltic lavas were erupted from highland volcanic vents; these lavas flowed over much of the island.^[116] For the last 4 million years, there have been no significant volcanic eruptions on the island and La Gomera has been in the erosional stage of its development.^{[117][118][119][120]} (The island's last volcanic eruption was a minor monogenetic eruption at Barranco del Machal, during the Early Pleistocene, about 1.94 Ma).^[121] Erosion has exposed the deeper parts of the volcanic edifices, revealing volcanic plugs, dykes, cone sheets, and lower lava flows.^[122]

Volcanic eruptions may resume on La Gomera in the future, but some geologists have suggested that La Gomera is already volcanically extinct.^[123][124]

La Palma's submarine seamount formed from 4 Ma to 3 Ma, in the Pliocene Epoch. The seamount stage rocks are layers of basaltic to trachytic pillow lavas with hyaloclastites and pillow breccias. The seamount's volcanic rocks have been intruded by younger mafic plutons and a mafic dyke swarm. Between 3 Ma and 1.77 Ma, the seamount rocks were uplifted, tilted and eroded. The structurally deepest rocks of the seamount have been metamorphosed to greenschist facies.^[125] Small remnants of the seamount stage rocks are now exposed on La Palma as its "Basal Complex", for example in Barranco de las Angustias.^{[126][127][128]}

La Palma's shield-building stage began at 1.77 Ma - the Garafía shield volcano grew, on top of the seamount, between 1.77 Ma and 1.20 Ma (forming the present-day northern part of La Palma), with the oldest subaerial lavas dated to 1.7 Ma. This shield volcano grew quickly to a height of about 3,000 m (9,800 ft) and a diameter of about 23 km (14 mi) but this volcano became unstable and its southern flank collapsed in a large landslide at 1.2 Ma.^[129] Only a small part of Garafía shield volcano is visible now because much has been eroded away or is buried by younger lavas. After the Garafía landslide, the focus of volcanic activity moved slightly to the south, producing another shield volcano, named Taburiente volcano, on top of Garafía shield volcano's collapsed southern flank.^[130]

For most of its active period, Taburiente shield volcano erupted basaltic lavas but final phases of its formation included phonolitic and trachytic lavas.^[131] Together, the three successive, superimposed shield volcanoes (the seamount, Garafía and Taburiente) form the Northern Shield.^[132]

A three-armed Y-shaped volcanic rift system developed at Taburiente volcano; this northern La Palma rift system had three radial arms - northwest, northeast and south - meeting at the shield volcano's summit. Gradually, most of Taburiente's volcanic activity became focused on the south rift.^[133] From 810,000 to 560,000 years ago, the southern part of Taburiente shield volcano's edifice grew by volcanic eruptions at the south rift; these eruptions formed Cumbre Nueva, a 10 km-long (6 mi) north-south volcanic ridge in what is now central La Palma.^{[134][135][136]} Cumbre Nueva had a period of particularly rapid growth from 621,000 to 566,000 years ago.^[137]

Taburiente volcano grew to an estimated maximum height of about 3,000 m (9,800 ft)^[138] but, about 525,000 years ago,^[139] its edifice became unstable and part of its southern flank (including much of the west flank of Cumbre Nueva) collapsed laterally in a landslide with a volume of more than 200 km³ (48 cu mi),^[140] resulting in the formation of a large crater named "Caldera de Taburiente"; it is an erosion caldera formed by mass wasting, not a collapse caldera formed by volcanic eruption. The Caldera de Taburiente is a topographic depression; from the time of the landslide until the present day, it has been enlarged by erosion and is now 15 km (9.3 mi) long, 6 km (3.7 mi) wide and 1.5 km (0.93 mi) deep.^{[141][142][143][144]} Also after the landslide, Cumbre Nueva grew rapidly again until about 490,000 years ago.^[145] A small stratovolcano, named Bejenado volcano, started forming on the floor of the Caldera de Taburiente about 523,000 years ago; it erupted lavas until about 491,000 years ago.^[146] Eruptions of lava occurred at Taburiente volcano until about 400,000 years ago.^{[147][148][149]} Volcanic activity then appears to have paused for the next 275,000 years.^[150]

About 125,000 years ago,^[151] the focus of volcanic activity moved south again, with eruptions of mostly mafic alkaline lavas gradually forming Cumbre Vieja, a 20 km-long (12 mi) ridge-shaped elevated rift zone volcano that has grown until the present day at southern La Palma's north-south volcanic rift zone. Cumbre Vieja reaches 1,949 m (6,394 ft) in height and it dominates the geology of the southern half of the island.^{[Note 3][153][154][155]} From 125,000 to 20,000 years ago, volcanic eruptions occurred on all arms of southern La Palma's triple-armed volcanic rift system. Between 20,000 and 7,000 years ago, volcanic activity declined on the northwest arm and stopped completely on the northeast arm.^[156]

During the Modern Era, eight confirmed eruptions have occurred at Cumbre Vieja, making La Palma the most volcanically active of the Canary Islands and accounting for half of all the volcanic eruptions in the Canary Islands during this c. 540 year timespan.^[157][158] These Modern Era eruptions have mostly been of the strombolian type, forming cinder cones; magmas have been predominantly mafic in composition but some more felsic phonolites have also been produced.^[159] Cumbre Vieja is still volcanically active; its three most recent eruptions are Nambroque (1949), Teneguía (1971) and Tajogaite (2021).^[160] Geologically recent volcanic eruptions have also occurred along the submarine section of the north-south rift zone that extends about 20 km (12 mi) beyond the southern tip of the island.^[161]

Day et al. (1999)^[162] suggested that the west flank of Cumbre Vieja is in the initial stages of instability. Modelling by Ward and Day (2001, 2005)^[163][164] led them to suggest that if a large landslide of Cumbre Vieja's volcanic rocks were to occur in the next few thousand years, it could displace a large volume of ocean water that would cause widespread tsunami damage along Atlantic Ocean coastlines. This suggestion has been opposed by some geologists who assess southern La Palma's volcanic rift zone to be stable and any generated tsunami would be much smaller than the modelled size, suggesting that Cumbre Vieja's collapse and damage scenarios would be less severe than Ward, Day and some popular science television documentaries have claimed.^[165][166] (See also: Cumbre Vieja tsunami hazard and Megatsunami).

El Hierro is the youngest and smallest of the seven main Canary Islands.^[167] El Hierro is in its shield-building stage.^[168]

During the Early Pleistocene, a submarine seamount grew upwards from the ocean floor, almost to sea level, on top of Cretaceous-Pliocene oceanic sediments.^[169][170]

Then, at 1.2 Ma, Tiñor shield volcano began to form on top of the seamount.^[171] Tiñor volcano's first subaerial lava was erupted at 1.12 Ma.^[172] Tiñor grew by erupting lavas across what is now the eastern half of El Hierro until about 882,000 years ago; the eruptions were mostly of effusive basaltic lava but there was also an explosive, xenolith-rich last eruptive phase (the Ventejís volcanics).^[173] Instability in the edifice of Tiñor volcano resulted in the Tiñor lateral collapse landslide at about 882,000 years ago when much of the volcano's northwest flank slid downwards and onto the ocean floor.^[174][175] This left a curved bay where the volcano's flank had been.

About 545,000 years ago,^[176][177] El Hierro's second subaerial shield volcano, named El Golfo volcano (also known as the El Golfo-Las Playas Edifice),^[178][c] started erupting. Its summit was slightly to the west of Tiñor volcano. Lavas from El Golfo volcano filled the bay that had been formed by the Tiñor landslide. El Golfo volcano's later lava flows covered the remains of Tiñor volcano. At its maximum development, El Golfo volcano was about 2,000 m (6,600 ft) high, about 20 km (12 mi) in diameter, with a surface area slightly larger than present-day El Hierro and about twice the area that Tiñor volcano had covered.^[179][180] El Golfo volcano grew by erupting lava from a Y-shaped rift system with west-north-west, north-north-east and south-south-east arms; most of the eruptions occurred on the west-north-west and north-north-east arms.^[181] Late-stage eruptions were of more differentiated lavas. El Golfo volcano gave El Hierro a roughly circular shape at this time.^[182] Eruptions occurred at El Golfo volcano until about 176,000 years ago.^[183]

The volcanic edifices of El Hierro were affected by at least two other large lateral collapse landslides of uncertain age:^[184] (1) the El Julán lateral collapse, in which much of the southwest flank of El Golfo volcano slid downwards and onto the ocean floor, occurred at least 158,000 years ago;^[185] (2) at least 145,000 years ago, the Las Playas lateral collapse occurred on the southeast flank of El Golfo volcano. At about the same time, slumping nearby did not result in complete downward slumping of El Golfo volcano's southeast flank into the ocean. Instead, a large detached block of rock moved about 30 m (98 ft) down a fault plane (the now inactive San Andrés fault) in what has been described as an "aborted" lateral collapse.^[186][187]

El Hierro's third, and current, major phase of volcanic activity is rift volcanism; it started about 158,000 years ago.^[188][189] This rift volcanism occurs at a Y-shaped volcanic rift zone system with west-north-west, north-north-east and south-south-east arms that meet at the centre of the island; all of the three rift arms have been very volcanically active.^[190][191] About 200 monogenetic cinder cones occur along the ridge crests of the three rift zones (the highest density of such cones in the Canary Islands).^[192] Rift phase lavas cover most of the island, not only forming the ridges along each rift zone but also partially infilling the landslide bays. The rift zones extend outwards as submarine volcanic ridges on the ocean floor; for example, the south-south-east rift zone extends underwater to at least 40 km (25 mi) south of the island.^[193]

Instability in the edifice of El Golfo volcano resulted in El Hierro's youngest and largest landslide, the El Golfo lateral collapse landslide, when a large part (with a volume of 180 km³ (43 cu mi)) of the volcano's northern flank slid downwards off the island and onto the ocean floor; individual blocks of moved material, up to 1,200 m (3,900 ft) across, have slid as much as 65 km (40 mi) from their original positions.^[194][195] This landslide formed the curved 14 km-wide (8.7 mi) El Golfo bay and a curved landslide scar depression, where the volcano's flank had been; the bay still forms the curved northwest coast of El Hierro.^[196] The El Golfo landslide scarp is preserved today as a 26 km-long (16 mi) cliff with a maximum height of 1,400 m (4,600 ft); the cliff is roughly parallel to the coast but about 2–4 km (1.2–2.5 mi) inland, except at each end, where the cliff meets the coast. The age of the El Golfo lateral collapse landslide is poorly constrained; it occurred sometime between 133,000 and 13,000 years ago. Evidence found on land favours the older end of this age range; evidence on the ocean floor favours a young age. Carracedo et al. (1999)^[197] have suggested that the conflicting evidence from land and ocean floor can be reconciled if there were two landslides instead of a single event: first, a collapse of the subaerial part of the El Golfo volcanic edifice at 133,000 years ago, then a submarine landslide at 13,000 years ago.^[198][199]

It has been estimated that the large landslides on El Hierro removed more than two-thirds of the total volume of lava erupted subaerially by the two shield volcanoes and the rift cinder cones of the island.^[200] This removal of lava has hampered efforts to estimate El Hierro's magma production and eruption rates.^[201]

The most recent volcanic eruption on land at El Hierro occurred 2,500 years ago. Its source was a small vent located on the north-north-east rift.^[202]

In 2011, a period of seismic unrest (associated with underground movements of molten magma) was followed by El Hierro's most recent volcanic eruption, which occurred underwater on the volcanic rift about 2 km (1.2 mi) south of the southern tip of the island.^[203] From October 2011 to March 2012, lava erupted from a submarine volcanic vent, which was later named Tagoro.^[204][205] Initially, this volcanic edifice was at a depth of 350 m (1,150 ft) but, by the end on the eruption, the edifice had grown to 88 m (289 ft) below sea level.^[206]

The seismicity of the Canary Islands is low. Earthquakes that occur on or near the Canary Islands are linked to volcanism and tectonism: scenarios include underground magma movement in dykes or magma chambers, normal faulting and reverse faulting.^[207] On the Modified Mercalli Scale (an earthquake intensity scale ranging from I for "not felt" to XII for "extreme"), most earthquakes in the region have had an intensity of VI or less. The Timanfaya eruptions on Lanzarote in 1730, however, were accompanied by earthquakes with intensities of up to X on the same scale.^[208] Earthquakes of intensity VII have occurred on La Palma (1677, 1920), on Gran Canaria (1913), and on Fuerteventua (1915, 1917).^[209]

From 1 January 1975 to 31 December 2023, 168 earthquakes of magnitude 2.5 or larger, with epicentres on or close to the Canary Islands, were recorded; the largest of these earthquakes had a moment magnitude of 5.4 and an intensity of VII with its epicentre on the ocean floor about 28 km (17 mi) west of El Hierro in 2013.^[210]

In 2004, an earthquake swarm occurred on Tenerife, which raised concern that a volcanic eruption may have been about to occur but no such eruption followed the swarm.^[211][212]

Earthquake swarms, due to the underground movement of molten magma, were detected before and during the volcanic eruptions of 2011–2012 and 2021. In the week before the 2021 eruption on La Palma, a swarm of more than 22,000 earthquakes occurred, with mb_Lg magnitudes up to about 3.5. The hypocentres of successive earthquakes migrated upwards as magma rose slowly to the surface.^{[213][214][215]} During the eruption, larger earthquakes were detected, for example an earthquake of mb_Lg magnitude 4.3 occurred 35 km (22 mi) below the surface.^[216]

At least four tsunamis, triggered by distant earthquakes, have hit the coasts of the Canary Islands in the Modern Era. They occurred in 1755 (1755 Lisbon earthquake), 1761 (1761 Lisbon earthquake), 1941 (1941 Gloria Fault earthquake) and 1969.^[217]

• Canary Islands Seamount Province
• Geology of Cape Verde
• Geology of Madeira
• Geology of Morocco
• Longshore drift – Sediment moved by the longshore current
• Pico do Fogo – Mountain peak in Cape Verde

• Carracedo, Juan Carlos; Day, Simon (2002). The Canary Islands (Classic Geology in Europe). Terra Books. ISBN 978-1903544075.
• Carracedo, Juan Carlos; Troll, Valentin R. (2016). The Geology of the Canary Islands. Amsterdam: Elsevier. ISBN 978-0-12-809663-5.

Sovereign states