Why the Canary Islands are Like This

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The current eruption on La Palma in the Canary Islands is now over a month old. Already the island’s largest in a hundred years, it’s giving no signs of stopping just yet. Volcano lovers have thrilled to its spectacular Strombolian explosions. Residents have endured disruption, displacement, and loss of homes and livelihoods. Dogs trapped by lava flows had to be fed by drone before they were taken to safety in a daring and mysterious rescue. Living with a live volcano is far from easy and seldom safe.

Plenty of news agencies, vloggers, and blogs are keeping us up to date on the progress of the current eruption. I’m going to take us deep into the past, on a journey into the island’s origins and evolution. We’re going to see the slow, steady pas de deux between a mantle plume and the plate above it. We’ll watch underwater volcanoes go subaerial, building new land, and see catastrophic collapses tear their confections down. We’ll learn the life stages of a Canary Island, and by the end, we’ll know the broad outlines of La Palma’s destiny.

In the end, we’ll see that this current eruption is as much an act of creation as it is destruction.

Mirador de La Tarta, Tenerife. Yes, it’s literally called a cake! The white layer is pumice, the black layers are basaltic scoria, and the reddish-brown layers are oxidized basaltic tephra. Credit: H. Zell (CC BY-SA 3.0)

La Palma’s Geologic Milieu: The Canary Archipelago

Just off of Cape Juby on the northwest African coast, a mere 100 kilometers from Morocco, lies a hotspot track. The Canary Hotspot, which first blowtorched through the Jurassic-aged ocean crust around 68 million years ago, has created a chain of volcanic islands and seamounts roughly 700 – 800 kilometers long and around 400 kilometers wide: together, they form the Canary Volcanic Province. The hotspot track trends generally northeast to southwest, as the African plate slides over it at a leisurely 2-ish centimeters a year.

The Canary Archipelago. Credit: Oona Räisänen (public domain)

The Canary Islands are hotspot volcanoes, but they’re not quite the same as the Hawaiian Islands. The Hawaiian archipelago’s oldest islands are extinct, with recent eruptive activity confined to the young Big Island and its nearby Lōʻihi Seamount. The Canary archipelago’s islands are generally younger with more active volcanoes as you head west toward the current location of the hotspot, but many of the older islands still have volcanic life in them, with documented historic eruptions. This isn’t because the hotspot is stuffing the region so full of magma it can’t cope – the supply is actually lower than Hawaii’s robust hotspot. It’s more likely because the Pacific plate is moving at a gallop compared to the African plate; one plate races over its hotspot while the other ambles, and so magma generated by the Canary hotspot doesn’t have far to travel in order to reach older islands.

Magma is also a bit more complex on the Canaries. They have an unusually long span of active volcanism combined with the hotspot’s desultory magma production, which leads to more “evolved” magmas. Many of the Canary Islands volcanoes erupt phonolitic magmas, which are intermediate between mafic magmas like basalt and felsic magmas like dacite. You can catch Canary Islands volcanoes extruding anything from basalt to rhyolite, and they exhibit a dizzying array of volcanic types, from fissures and shields all the way to classic composite cones.

And the Canary hotspot isn’t alone in the region. There’s at least one more: the Madeira hotspot forms a track roughly parallel to the Canary hotspot, and is almost exactly the same age and length (though their magma compositions point to individual sources). Nearly-twin hotspots! And they’re just two members of a family of hotspots in the region. This is a volcanically intriguing area, and we’ll likely be returning to it for a deeper dive in the future.

Detail of the Canary and Madeira hotspots. Modified from Mjelde et al (2010)

The Life Stages of the Archipelago

Volcanic island arcs produced by hotspots have a general lifecycle, which is beautifully displayed in the Canaries, with a few twists.

First, let’s follow Carracedo’s lead and split the islands into three groups:

1. Recently active (eruptions within the past 500 years): Tenerife, Lanzarote, El Hierro, and La Palma

2. Active within the Quaternary period: Fuerteventura and Gran Canaria

3. Quiescent during both Quaternary and recent times: Gran Canaria

Now we can situate them within their life stages, each of which will last for several million years.

Seamount/Emergent Stage

Volcanic islands begin and end here: as nubs rising from the sea floor, either becoming or having once been mighty mountains. We take on this stage as a beginning: when mafic and ultramafic magmas form plutons, dyke swarms, the hearts of future islands. Submarine eruptions spill out piles of pillow lavas and hyaloclastites; seafloor sediments are incorporated. Eruptions grow the pile higher and higher: if they persist, they will build a seamount that fitfully breaks the surface, replacing in eruptions what the erosive waves steal in between, until an island emerges at last.

Every single one of the Canary Islands has passed through this stage already. The Las Hijas seamounts, growing 70 kilometers southeast of El Hierro, may become the newest Canary Island in a few million years.

Shield Stage

This is the vigorous youth of the island, a period of prodigious lava production and (relatively rapid) growth. Frequent eruptions pile layer after layer of lava flows and pyroclastic debris on its core and flanks. But it’s not all uninterrupted growth! As dykes wedge in, feeding eruptions, and ever-steepening eruptive products pile on to the flanks, occasional catastrophic lateral collapses occasionally send massive portions of the island crashing down into the ocean, leaving massive embayments and landslide scarps behind. Then, the island’s volcanoes continue building up what gravity so dramatically tore down.

And yeah, there are tsunamis caused by these events. But despite speculation earlier this century, they’re not actually likely to spawn ocean-spanning megatsunamis. Sorry.

La Palma and El Hierro are in the shield stage. Some sources place Tenerife here, too, but I beg to differ.

Charco Azul on El Hierro. This is one of the most stunning volcanic coastlines in the world, and a testament to what a young volcano can build. Click on photo for a full-size image. Credit: Areuland (CC BY-SA 4.0)

Declining stage

This is a fuzzy phase, where the magmas contain trachytic and phonolitic components, and the eruptions begin to wane.

Erosional/Repose stage

This is a quiescent stage where eruptions cease and erosion dominates. All of the Canaries have passed through this phase, excepting the two young ‘uns La Palma and El Hierro. La Gomera has probably returned to it.

Rejuvenation/Post-erosional stage

Eruptions return! They can be quite different than shield stage, however: they’re separated by longer intervals, generally don’t produce as much volume, and can generate some pretty highly evolved magmas, as they cook longer in the chambers. Oddly for oceanic arcs fed by hotspots, the activity in the rejuvenation stage can produce some pretty impressive stratovolcanoes containing lavas with a high silica content. Mount Teide on Tenerife and Pico de las Nieves on Gran Canaria are impressive examples.

Most of the Canary Islands are hanging out in this stage: Tenerife, Gran Canaria, Lanzarote, and Fuerteventura.

(Fun fact: Fuerteventura and Lanzarote are basically a single volcanic ridge, and would be one big happy island if it wasn’t for the dip in the middle low enough for current sea levels to drown.)

Timanfaya National Park, Lanzarote. It’s a spectacular example of the volcanism of the rejuvenation stage. Credit: Justraveling.com/Flickr

Volcanic Rejuvenation: Not the Only Secret to the Canaries’ Longevity

You’d expect the older islands to be back to seamounts by now, despite their desultory bits of volcanic activity. But they have a few secrets to their staying power. For one thing, the oldest, eastern islands are close to the continental margin, and hence on seafloor that’s considerably shallower (about 1000m) than the depth on the western side of the archipelago (about 4000m). Considering how massive they become in the shield stage, it’ll take a lot of wear and tear to get them down below sea level.

They’re also riding on older, colder, thicker crust than chains like the Hawaiian Islands, so despite their weight, they don’t subside very much. Were that not so, and if they were sinking at the same rate as the Hawaiian archipelago, only El Hierro and La Palma would currently be holding their heads above water. It’s kind of wild to think about!

So that’s our milieu, within which the really dramatic stuff is currently happening on La Palma. Next, we’ll take a deep dive through that island’s deep time, and see what made it the fire-breathing beauty it is today.

References:

Acosta et al (2003): Comparison of volcanic rifts on La Palma and El Hierro, Canary Islands and the Island of Hawaii. Marine Geophysical Researches 24: 59–90

Barker et al (2015): The magma plumbing system for the 1971 Teneguía eruption on La Palma, Canary Islands. Contributions to Mineralogy and Petrology vol 170 #54

Fernández et al (2021): Detection of volcanic unrest onset in La Palma, Canary Islands, evolution and implications. Scientific Reports 11, 2540

Groom, Simon: An integrated study of the magmatic products linked to the Cumbre Nueva Collapse, La Palma. Dept. Earth and Planetary Sciences, Birbeck, University of London (Unpublished PhD Thesis)

Klügel et al (2000): The chemically zoned 1949 eruption on La Palma (Canary Islands): Petrologic evolution and magma supply dynamics of a rift zone eruption. Journal of Geophysical Research vol. 105 iss. B3, pgs. 5997– 6016

Mjelde et al (2010): Global pulsations of intraplate magmatism through the Cenozoic. Lithosphere. 2. 361-376. 10.1130/L107.1.

Prieto-Torrell et al (2021): Modelling and simulation of a lava flow affecting a shore platform: a case study of Montaña de Aguarijo eruption, El Hierro (Canary Islands, Spain). Journal of Maps Volume 17, 2021 – Issue 2 pgs 502-511

Torres-González et al (2020): Unrest signals after 46 years of quiescence at Cumbre Vieja, La Palma, Canary Islands. Journal of Volcanology and Geothermal Research, Volume 392, 106757

Troll, V. and Carracedo, J. (2016): The Geology of the Canary Islands. Elsevier

Viñuela, J.M. (2007). “The Canary Islands Hot Spot” (PDF). www.mantleplumes.org.

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Dana Hunter, October 27, 2021. Earth Science, Volcanoes archipelago, Canary Hot Spot, Canary Islands, eruption, geology, history, hot spot, island arc evolution, island arc stages, La Palma, lava, natural disaster, Volcano

About Dana Hunter

Confirmed geology aficionado Dana Hunter is a science writer whose work has appeared in Scientific American, the New York Times, and Open Lab. She explores the earth sciences with an emphasis on volcanic processes, regional tectonics, and the intersection of science and society, sometimes illustrated with cats. Join her at unconformity.net for epic adventures in the good science of rock-breaking.

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