Geology of the Canary Islands

The seven main Canary Islands originated as separate submarine seamount volcanoes on the ocean floor, which is 1,000–4,000 m (3,000–13,000 ft) deep in the Canarian region.

[19] The seven main Canary Islands originated as separate submarine seamount volcanoes on the floor of the Atlantic Ocean (although Tenerife and La Gomera are close enough to each other for their seamounts to overlap as they grew;[21] the distance between Lanzarote and Fuerteventura was also small enough for some of their shield volcanoes to overlap as they grew, forming a single volcanic ridge[22]).

The two oldest, eastern islands of Fuerteventura and Lanzarote, where fissure eruptions have dominated in the rejuvenation stage, have more subdued topography with heights below 1,000 m (3,300 ft).

Seamount stage rocks are not exposed on Lanzarote, Tenerife, Gran Canaria and El Hierro, which has hindered dating of the earliest underwater volcanic activity at these islands.

There are small amounts of migmatite and hornfels that outcrop in contact aureoles bordering igneous intrusions in the Basal Complex of Fuerteventura.

[37] 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.

The bar chart compares the number of volcanic eruptions (vertical y-axis) at different stages during this time span (horizontal x-axis).

[57] Geologically recent examples of Lanzarote's rejuvenation stage volcanism include eruptions at Montaña Corona (about 21,000 years ago), Timanfaya (1730–1736) and Tao/Nuevo del Fuego/Tinguatón (1824).

[68] 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.

[19] The igneous rocks of the Basal Complex probably represent the seamount stage of Fuerteventura's volcanic history, exposed due to uplift and erosion.

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.

[79] At least three shield volcanoes were active during this stage of island development and their lava flows gradually merged into a single large landform.

[80] 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).

[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.

[81][45] 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.

[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).

[101][102][103][104] Tenerife is currently at the point in its geological development where the effects of constructive volcanic eruption and destructive erosion are roughly balanced.

[109][107][110] 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 these old lavas instead represent early subaerial shield volcano eruption material that flowed off the island into the ocean.

[127] Small remnants of the seamount stage rocks are now exposed on La Palma as its "Basal Complex", for example in Barranco de las Angustias.

[142] About 125,000 years ago,[143] 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.

[146][147] These historical 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.

[148] 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.

[175][161] 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.

[183] A group of three seamounts called Las Hijas (Spanish for 'The Daughters') are located on the ocean floor 70 km (43 mi) southwest of El Hierro.

This includes at some volcanic cones, for example Montaña de El Palmar in northwest Tenerife where basaltic lapilli tephra (known locally as "pincòn") has been removed for use as horticultural substrate.

[241] The sedimentary rock calcrete (also known as caliche) was extracted at some quarries in southwestern Gran Canaria, then heated in kilns to produce lime for use in construction.

[242] Ore deposits of some rare-earth elements have been found in two settings in the Canary Islands: (1) pegmatitic syenites of southwest Tenerife and northeast La Gomera; (2) carbonatites in the Basal Complex of northwest and central Fuerteventura.

[243] The potential exploitation of shallow high-enthalpy geothermal energy resources (originating from volcanic heat in bedrock) has been investigated on Lanzarote, Tenerife and La Palma.

TFGeoturismo has published a guide promoting the role of Tenerife in the history of science, describing 18 locations along the route of Alexander von Humboldt's notable 1799 journey from Puerto de la Cruz to the summit of Teide.

[258] The sedimentary rocks under the ocean between the eastern islands of the Canarian archipelago and Africa, e.g. the Fúster Casas Trough, are believed to contain hydrocarbons.