Algar do Carvão

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Algar do Carvão
Algar do carvao, gruta 20.jpg
Algar do Carvão, Boca do algar
Location Terceira Island, Azores
Coordinates 38°43′44″N 27°11′7″W / 38.72889°N 27.18528°W / 38.72889; -27.18528Coordinates: 38°43′44″N 27°11′7″W / 38.72889°N 27.18528°W / 38.72889; -27.18528
Depth 90 meters
Length 100 meters
Discovery 1893
Geology Lava tube
Access Public

The Algar do Carvão is an ancient lava tube or volcanic vent located in the center of the island of Terceira in the Azores. It lies within the municipality of Angra do Heroísmo in the parish of Porto Judeu.


The word, algar, is a Portuguese word that denotes a natural cavity in the earth that, unlike most caves or caverns, is vertical in its orientation, like a well. The Portuguese word derives from the Arabic word, al-Gar, which means "the crease". Carvão means "coal" in Portuguese, but the Algar do Carvão is not a source of coal; so, to call this geological feature "coal cavern" is more an acknowledgment of its darkness than the composition of the rock in which it was formed.


Entrance to the Algar do Carvão
Stalactites in the Algar do Carvão

Terceira is the site of four large volcanoes (Pico Alto, Santa Barbara, Guilherme Moniz, and Cinco Picos) grouped along a basaltic fissure zone that transects the island from northwest to southeast. The Algar do Carvão is directly associated with the caldera of the Guilherme Moniz volcano, but it is part of the same complex as Santa Barbara to the west, Pico Alto to the north, and Guilherme Moniz, which is a short distance to the south of the Algar do Carvão site.

At Algar do Carvão, which is at an altitude of about 550 meters above sea level, it is possible to descend about one hundred metres into the earth where there is a pool of crystal-clear water. The cave itself is remarkable for the unique mineralogical characteristics of its silicate stalactites. The site, 40.5 hectares in extent, has been designated a “regional natural monument”.

The existence of the cavern was known for a long time, but the lack of light inside it, and the obvious danger of a vertical descent into the darkness, delayed any real exploration. On 26 January 1893, the first descent, " ... with the use of a simple rope, was accomplished by Cândido Corvelo and Luis Sequeira." The second descent was made in 1934, by Didier Couto, who produced the first rough map of the interior. This drawing, based on visual observations alone (rather than measurements), turned out to be quite accurate. On 18 August 1963, a group of enthusiasts organized a descent using a "chair" platform suspended on a nylon line and, later, a harness. Now, with the use of portable lighting systems, it has become possible to increase the numbers of people who can examine, at first hand, the most remote and narrow sections of the cavern.

The site is open to the public daily, except weekends and holidays, from May to September, between three o’clock and five o’clock in the afternoon. Access to the site on other occasions may be arranged through "The Mountaineers” (Montanheiros), the organization that takes care of matters related to the Algar.