Morocco’s Parliament approved two unilateral legislative initiatives in 2017 aimed at claiming waters off the coast of Western Sahara and demarcating its maritime border with the Canary Islands. This legislation expanded Morocco’s territorial waters to include prized underwater mountains, leading to a dispute with Spain over territory claimed before the United Nations.
Underneath the Atlantic Ocean, south of the Canary Islands, lies a series of underwater mountains known as the “grandmothers of the Canaries.” These formations, remnants of ancient islands that succumbed to the sea, have gained geopolitical significance due to large deposits of rare earth minerals such as tellurium, cobalt, and nickel, essential for high-tech industry.
Five underwater mountains were initially discovered, followed by eight more. Among them, Mount Tropic stands out. At 119 million years old, it is a volcano whose summit is about 1,000 meters below the surface, with a diameter of approximately 50 kilometres. This submerged mountain reaches heights of 3,200 meters, making it one of the tallest in the volcanic province of the Canary Islands, although it lies outside the current 200-nautical-mile boundary of Spanish waters.
Tropic is located over 250 nautical miles from the nearest part of the Canary Islands, at coordinates 20.72 degrees West, 23.89 degrees North. It is 499 kilometres (269 nautical miles) from the port of La Restinga in El Hierro and 677 kilometres (360 miles) from Maspalomas, Gran Canaria.
In terms of geographical ranking, Tropic is the second tallest underwater mountain after Echo, which rises 3,400 meters from a depth of 3,700 meters. Its nearly circular shape suggests long-term volcanic activity, with signs of ancient landslides evident in its structure.
British scientists brought worldwide attention to Mount Tropic in 2017 when the UK’s National Oceanography Centre and research teams reported significant quantities of tellurium found in ferromanganese crusts covering the mountain. The BBC reported that estimates indicated about 2,670 tonnes of tellurium could be present, equivalent to one-twelfth of global demand for the metal. Samples collected showed tellurium concentrations 50,000 times higher than those typically found on land.
Expedition leader Bram Murton described the crust as “astonishingly rich,” highlighting the rocks’ immense value as resources. Scientific evaluations suggested that the amounts of cobalt and tellurium could support the construction of 277 million electric cars and produce enough solar panels to meet half of the UK’s electricity needs.
Before the British findings, Spain had conducted several oceanographic surveys in the area since 2011, aiming to document the geological characteristics of these mountains and assert sovereignty over this maritime zone at the UN. In 2014, Spain formally requested an extension of its continental shelf in a region between 200 and 350 nautical miles, an area that includes Mount Tropic, covering a total of 296,000 square kilometres—almost the size of Italy.
After the discovery of Tropic’s mineral wealth became known, Morocco introduced legislation in July 2017 to assert ownership over the waters of Western Sahara and further delineate its maritime boundaries with the Canaries. This was followed by unilateral approval of two laws in December 2019 to expand its territorial waters towards the Saharan coast, intensifying the dispute with Spain over these underwater resources.
Although the sovereignty of these waters and the surrounding airspace has become a contentious issue between the two nations, discussion of these matters has recently taken a backseat in diplomatic relations. In a meeting in December 2025, both countries signed a joint declaration to reopen customs in Ceuta and Melilla, while leaving the complex issue of territorial waters unresolved.
Meanwhile, in 2021, the Canarian Parliament called on the Spanish government for a moratorium on underwater mining at Mount Tropic pending investigation into potential environmental impacts. This proposal, put forth by Ecologistas en Acción Lanzarote, also sought to designate the area as one of ecological or biological significance.
