Mid-Atlantic Ridge (Tentative List)

The Mid-Atlantic Ridge is a natural nomination inscribed on Portugal’s UNESCO Tentative List since 6 June 2017. Although the Mid-Atlantic Ridge extends for more than 16,000 kilometres, from the Arctic to the Antarctic, and is the longest mountain range on the planet — with more than 90% of its length submerged —, the Portuguese nomination is confined to the stretch that surfaces and rises in the archipelago of the Azores. It is therefore a proposal of a geological and oceanographic nature, distinct from the monumental properties that dominate the national list.

An archipelago on the boundary of the plates

The Azores arose from one of the most singular tectonic settings on the globe: the vicinity of a triple junction where the Eurasian, African and North American plates meet. The Mid-Atlantic Ridge crosses the archipelago, leaving the islands of Flores and Corvo on the North American plate, to the west, and the remainder to the east. It is at this divergent boundary that new oceanic crust is continuously formed, further fed by the Azores mantle hotspot, located east of the ridge, in the vicinity of the central group.

Mount Pico, at 2,351 metres, is the highest point in Portugal and one of the highest summits along the entire Mid-Atlantic Ridge — a mountain range that, almost in its entirety, lies invisible beneath the ocean.

The proposed property is not limited to the emerged land. It encompasses the nine inhabited islands and their nearly six hundred islets, the territorial waters and the vast Azores Plateau, a structure of roughly triangular outline, delimited by the 2,000-metre bathymetric contour, which occupies some 400,000 km². This plateau, associated with the crustal thickening generated by the hotspot, harbours not only the islands but also numerous seamounts.

Natural values of universal significance

The nomination is based on natural criteria. Under the criterion of exceptional scenic beauty, it evokes the singularity of landscapes such as Mount Pico, which rises abruptly from the ocean floor and, in winter, contrasts the snow of the summit with the black basalt and the green of the island base. Under the criterion of major ongoing geological processes, it values the deep hydrothermal vent fields, which form in the divergent zones where new crust is born. These structures play a role in the thermal and chemical regulation of the oceans, and their study has contributed to new theories on the origin of life on Earth.

The proposal came to replace earlier, more restricted nominations centred on specific volcanic phenomena such as the Algar do Carvão and the Furna do Enxofre, broadening the scope to the entire Azorean island and submarine system. The relationship with the volcanism and viticulture of the islands is reinforced by the proximity to an already classified property: the Landscape of the Pico Island Vineyard Culture, inscribed on the World Heritage List in 2004.

Tentative List and the course of the nomination

Joining the Tentative List is a preliminary and mandatory stage of the designation process: in it a State Party registers the properties it is considering proposing for inscription on the World Heritage List. The presence of the Mid-Atlantic Ridge in this inventory signals Portugal’s intention, but does not yet constitute designation nor guarantee its realisation. The complexity of a property of such great marine extent — and its possible transnational coordination with other States bordering the ridge — poses specific challenges of delimitation and management.

Among the Portuguese natural proposals, the Mid-Atlantic Ridge dialogues with already recognised island properties, such as the Laurisilva of Madeira, affirming the weight of Atlantic natural heritage in Portugal’s contribution to the World Heritage Convention.