monte tropic canary islands submarine mountains

The underwater ‘grandmothers’ of the Canary Islands

Compiled with the help of artificial intelligence, based on Spanish-language information. Source below the article.

South of the Canary Islands, beneath the ocean, several peaks rise from the seabed. These were once islands but lost their battle against the waves and now lie hidden under thousands of metres of water. Known as the ‘grandmothers’ of the Canaries, they were given this name due to their immense age and their connection to the same volcanic forces that shaped the Spanish archipelago.

Rare earth riches

In recent years, these formations have gained prominence on the international geopolitical stage after it was discovered that they contain enormous quantities of so-called rare earth minerals such as tellurium, cobalt and nickel, which are highly sought after by the technology industry. First, five submarine mountains were found – Las Hijas, Echo, The Paps, Drago and Tropic – followed by another eight: Drago, Bimbache, Ico, Pelicar, Malpaso, Tortuga, Infinito and Las Abuelas. Of all of them, one peak draws particular attention: Monte Tropic.

An ancient giant

Tropic is a volcano some 119 million years old – five times older, for instance, than Fuerteventura, the geologically oldest Canary Island. Its summit lies around 1,000 metres below the surface, and it spans about 50 kilometres in diameter. This underwater mountain rises 3,200 metres from the ocean floor, making it one of the oldest in what geologists call the Canary Islands Volcanic Province in the Atlantic Ocean, although it officially lies beyond the 200-mile limit of Spanish waters.

Monte Tropic stands on seabed that is more than 250 nautical miles from the nearest point of the archipelago, at coordinates 20.72 degrees west and 23.89 degrees north. According to measurements provided by Google Maps, Tropic is exactly 499 kilometres (269 nautical miles) from the port of La Restinga on El Hierro, the southernmost point of the Canaries, and 677 kilometres (360 nautical miles) from Punta de Maspalomas on Gran Canaria, the archipelago’s second most southerly point.

Physical features and past activity

Within its geographical area, Tropic is the second tallest submarine mountain, after Echo, which rises 3,400 metres from a depth of 3,700 metres, and the second largest by surface area, after The Paps, which is 44 per cent bigger at 1,363 square kilometres. Its shape is that of an almost circular volcano, suggesting a long period of activity centred on a single point, but its slopes appear to show signs of major ancient collapses, similar to those visible today on El Hierro.

Teams from the Spanish Institute of Oceanography (IEO), the Geological and Mining Institute of Spain (IGME) and the Spanish Navy have studied the mountain. Among their findings, they discovered that it is crowned by a large flat plateau showing signs of having once been above sea level, before sinking at some undetermined point in the past to its current depth of 1,000 metres beneath the Atlantic.

A breakthrough discovery

It was in 2017 that Tropic moved from scientific obscurity to the international headlines. The UK’s National Oceanography Centre, together with the IGME and researchers from several universities, announced the discovery of large concentrations of tellurium – a metal highly valued in high-tech manufacturing – in the ferromanganese crusts covering the mountain. The BBC reported at the time that those behind the discovery calculated Tropic could contain around 2,670 tonnes of tellurium, equivalent to one-twelfth of global consumption of the metal.

The scientists explained that the plateau crowning Monte Tropic is covered by a rocky crust about four centimetres thick with extremely high concentrations of tellurium. In fact, samples brought up by underwater robots showed tellurium concentrations 50,000 times greater than those typically found in land-based deposits of the metal. The expedition leader, Bram Murton, said the crust was ‘astonishingly rich’, making these rocks ‘incredibly special and valuable from a resource perspective’.

Science magazine put figures to the discovery: if the calculations of the team that explored Tropic from the research vessel James Cook were correct, the mountain holds enough cobalt to build 277 million electric cars – 54 times the current global fleet – and enough tellurium to make solar panels that alone could cover half of the United Kingdom’s electricity consumption, the world’s seventh-largest economy.

Spanish interest predates UK expedition

However, years before the British scientific expedition’s findings became public, Spain had already carried out several oceanographic campaigns in the same area. As early as October 2016, the IGME, the IEO and the Complutense University of Madrid published an advance report in Ore Geology Reviews on the mineral wealth of Tropic and its neighbouring peaks Eco, Drago and The Paps, though without explicitly mentioning tellurium. This is the summarised composition of one of the samples from Tropic, designated DR16-13.

‘On its slopes and summit are extensive mineral deposits of ferromanganese crusts formed over the last 30 million years. Ferromanganese oxide deposits on the seabed represent the planet’s most important source of elements for manufacturing high-tech products and remain largely unexplored,’ the IGME said in 2016.

The Spanish campaigns, which date back to 2011, were aimed not only at understanding the geological characteristics of these submarine mountains and their ecosystems, but also at documenting a request to the United Nations to extend Spanish sovereignty over the maritime zone surrounding the Canaries beyond the 200-mile limit, including the ‘grandmothers’ of the archipelago. Indeed, in 2014 – three years before the British expedition – the Spanish government submitted a formal application to the UN to extend the Canary Islands’ continental shelf westwards over a strip of ocean lying between 200 and 350 nautical miles, with a total surface area of 296,000 square kilometres, equivalent to nearly the entire surface area of Italy. Monte Tropic falls within this area.

Geopolitical tensions

But once Tropic’s mineral wealth became known worldwide, Morocco approved in July 2017 two legislative proposals aimed at incorporating the waters of Western Sahara into its territory and delimiting its maritime border with the Canary Islands. Two years later, in December 2019, the Moroccan parliament unilaterally passed two laws extending its territorial waters towards the coasts of Western Sahara, a territory awaiting decolonisation, and including the coveted submarine mountains within them. This marked the beginning of a dispute between the two countries at the UN over sovereignty of the waters and their underwater resources.

So far, however, the issue of territorial waters and Western Sahara’s airspace has remained in the background in relations between the two nations. At a meeting held in December 2025, both countries signed a joint declaration on the reopening of customs posts in Ceuta and Melilla, but the thorny matter of waters and airspace was avoided.

Calls for protection

Meanwhile, in the Canaries, the regional parliament voted in 2021 – with the Popular Party and Ciudadanos voting against – to ask the Spanish government to impose a moratorium on deep-sea mining at Monte Tropic until the effects on the marine environment had been investigated. The proposal, drafted by Ecologistas en Acción Lanzarote, also called for the area to be declared a marine area of ecological or biological importance.

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