Geology of the Canary Islands



The geology of the Canary Islands is dominated by volcanic rock. The Canary Islands, and some seamounts to the north-east, form the Canary Volcanic Province. The volcanic history of this province started about 70 million years ago. The Canary Islands region is still volcanically active. The most recent volcanic eruption on land occurred in 2021 and the most recent underwater eruption was in 2011-12.

The Canary Islands are a 450 km long, east-west trending, archipelago of volcanic islands in the North Atlantic Ocean, 100-500 km off the coast of Northwest Africa. 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) from the edges of the African Plate.

From east to west, the main islands are Lanzarote, Fuerteventura, Gran Canaria, Tenerife, La Gomera, La Palma, and El Hierro. There are also several minor islands and islets. The seven main Canary Islands originated as separate submarine seamount volcanoes on the floor of the Atlantic Ocean, which is 1000–4000 m deep in the Canarian region.

Lanzarote and Fuerteventura are parts of a single volcanic ridge called the Canary Ridge. These two present-day islands have sometimes been a single island in the past. Part of the ridge is now submerged, and Lanzarote and Fuerteventura are separate islands, separated by an 11 km wide, 40 m deep strait of ocean water. Volcanic activity has occurred during the last 11,700 years on all of the main islands except La Gomera.

Regional setting
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 north of the Canary Islands. The northernmost of this group of seamounts, Lars seamount (about 380 km north of Lanzarote), has been dated to 68 Ma. The seamounts are progressively younger southwestwards towards Lanzarote.

The Canary Islands are built upon one 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. The oceanic lithosphere is about 60 km thick at the central Canary Islands and about 100 km thick at the western islands.

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.

Growth stages
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:
 * 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).

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.

The seven main Canary Islands originated as separate submarine seamount volcanoes on the floor of the Atlantic Ocean. 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 1000 m. The other islands are much more rugged and mountainous. The volcanic edifice of Tenerife, which is capped by Teide stratovolcano, rises about 7500 m above the ocean floor (about 3780 m underwater and 3715 m above sea level); it is the tallest volcanic edifice on Earth, except for a few in Hawaii.

The volume of volcanic rock that has built up the Canary Islands to thousands of metres above the ocean floor is about 124600 km3; 96% of this lava is hidden below sea level and only 4% (4940 km3) is above sea level. The western islands have more of their volume (7%) above sea level than do the eastern islands (2%).

Age
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).

Rock types
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.

Outcrops of plutonic rocks (for example, syenites, gabbros and pyroxenites) that formed deep below the surface occur on Fuerteventura, La Gomera and La Palma. Apart from some islands of Cape Verde (another volcanic island group in the Atlantic Ocean, about 1400 km south-west of the Canary Islands), Fuerteventura is the only oceanic island known to have outcrops of carbonatite.

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

Origins of volcanism
Several hypotheses have been proposed to explain the volcanism of the Canary Islands. Two hypotheses have received the most attention from geologists:


 * 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.

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 farther north). This is consistent with the African Plate rotating anticlockwise at about 12 mm per year. 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 1000 km in the upper mantle.

Volcanic eruption distribution
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). Sixteen of these eruptions have been during the Modern Era of European history (that is, after c. 1480). Therefore, in the last 500 years, volcanic eruptions have occurred, on average, every 30 to 35 years. However, in the Modern Era, the repose period between infrequent eruptions at each volcano has been highly variable (26 to 237 years for Cumbre Vieja on La Palma; 1 to 212 years for Tenerife), making reliable prediction of future eruptions unlikely.

Lanzarote
Volcanic activity at Lanzarote started during the Oligocene Epoch at 28 Ma. For about the first 12 million years, the lava pile of a submarine seamount built up from the 2500 m deep sea floor. 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. Between 10.2 Ma and 3.8 Ma, volcanic activity was focussed about 35 km to the northeast, forming a second shield volcanic island called Famara. Between Los Ajaches and Famara volcanoes, a central volcanic edifice was also active from 6.6 to 6.1 Ma. The edifices gradually merged to form a single island, Lanzarote, at about 4 Ma. From 3.9 Ma to 2.7 Ma, volcanic activity paused and the island was eroded. Today, although the lavas of Los Ajaches volcano are now mostly covered by calcrete, 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. 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. 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).

The Timanfaya eruption (1730–1736) erupted more than one billion cubic metres (1 km3) of lava, and a large volume of pyroclastic tephra, from more than 30 volcanic vents along a 14 km fissure in western Lanzarote. The lava flows cover one quarter of the island (an area of about 225 km2) with some of the flows reaching about 50 m 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.

Almost all the volcanic rocks of Lanzarote are basaltic.

Fuerteventura
Fuerteventura is situated on Mesozoic oceanic crust, about 70 km from the edge of the African continental shelf and about 100 km 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.

The two main rock sequences of Fuerteventura are (1) a lower, older (Cretaceous to early Miocene) sequence of sedimentary, plutonic and submarine 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. The sedimentary rocks of the basal complex were deposited on the seafloor 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. The igneous rocks of the basal complex probably represent the seamount stage of Fuerteventura’s volcanic history, exposed due to uplift and erosion.

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. 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. 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. These shield volcanoes erupted mostly basaltic and trachybasaltic lava flows.

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.

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

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.

Gran Canaria
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).

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. 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. 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.

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.

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 statovolcano in the central part of Gran Canaria. This produced lava flows, ignimbrites and debris avalanche deposits. The second phase (3.5 to 1.5 Ma) had strombolian-style effusive eruptions of lava flows along a northwest-southeast trending volcanic rift. The current phase, from 1.3 Ma to the present, has featured scattered phreatomagmatic and strombolian eruptions of very alkaline lavas. The most recent volcanic eruption on Gran Canaria occurred about 2,000 years ago at Bandama crater, in the northeast part of the island.

Sand dunes, with a total volume of 18 e6m3, cover an area of 3.6 km2 of the Maspalomas cuspate foreland on Gran Canaria's south coast. 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 – but some dunes reach 20 m thick. In a few areas, the underlying deltaic sediments are exposed. The sand that has built the dunes has been moved about 2 or 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. The dunes had long been thought to have formed during the last several thousand years 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.

Tenerife


Tenerife's subaerial shield stage of island development started at about 11.9 Ma in the late Miocene Epoch. 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. 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. 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. The lavas of these three shield volcanoes gradually formed a combined volcanic edifice that accounts for 90% of Tenerife's current volume.

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. 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). Central volcanic activity has been accompanied, since 3 Ma, by mostly basaltic fissure eruptions at three radial rift zones: the northwest, northeast and south rift zones. About 200,000 years ago, Las Cañadas volcano collapsed, forming Las Cañadas caldera. In this 16 x 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). Both of these stratovolcanoes are still active. Together with some satellite vents, they form the Teide-Pico Viejo Volcanic Complex. 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. Tenerife is currently at the point in its geological development where the effects of constructive volcanic eruption and destructive erosion are roughly balanced.

La Gomera
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. At the end of the seamount stage, the seamount's top surface was eroded. 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.

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

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.

In the early Pliocene, from 5.5 Ma to 4.2 Ma, basaltic lavas, erupted from highland volcanic vents, flowed over much of the island. 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. (The island's last volcanic eruption was a minor monogenetic eruption at Barranco del Machal, during the Early Pleistocene, about 1.94 Ma). Erosion has exposed the deeper parts of the volcanic edifices, revealing volcanic plugs, dykes, cone sheets, and lower lava flows.

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

Earthquakes
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. 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. Earthquakes of intensity VII have occurred on La Palma (1677, 1920), on Gran Canaria (1913), and on Fuerteventua (1915, 1917).

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 west of El Hierro in 2013.

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.

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 mbLg magnitudes up to about 3.5. The hypocentres of successive earthquakes migrated upwards as magma rose slowly to the surface. During the eruption, larger earthquakes were detected, for example an earthquake of mbLg magnitude 4.3 occurred 35 km below the surface.

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.