Algar do Carvão

Algar do Carvão
Main entrance to the cavern, as seen from with the cave
Profile of the Algar do Carvão with entrance, chamber and lagoon
Location	Terceira Island (Azores), Portugal
Coordinates	38°43′44″N 27°11′7″W / 38.72889°N 27.18528°W / 38.72889; -27.18528
Depth	90 metres (300 ft)
Length	100 metres (330 ft)
Discovery	26 January 1893
Geology	Lava tube, Basalt
Entrances	1
Access	Tours are available in season

The Algar do Carvão (Cavern of Coal) is an ancient lava tube or volcanic vent located in the central part of the island of Terceira in the Portuguese archipelago of the Azores. It lies within the civil parish of Porto Judeu in the municipality of Angra do Heroísmo.

History

The existence of the cavern had been known for a long time, but the depth and lack of ambient light, made any descent difficult, owing to the vertical descent, and delayed any real exploration.^[1]

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.

With the advent of portable lighting systems, it was possible to re-examine the observations first-hand, including the most remote and narrow sections of the cavern. The site was open to the public in the late 20th century, through weekly organized tours (except weekends and holidays) through the summer (from May to September). Access to the site is also possible through the Montanheiros (Mountaineers) organization, the group responsible for matters associated with the Algar.

Toponymy

The word, algar, is a Portuguese word that denotes a natural cavity in the earth that, unlike most caves or caverns, is more vertical in its orientation, like a well. The Portuguese word derives from the Arabic word, al-Gar, which means "the crease", while Carvão means "coal" in Portuguese. The Algar do Carvão is not a source of coal, and the term carvão has also been used in the Portuguese vernacular akin to "blackened", "sooty" or "burnt", referring to the dark composition of the rocks.

Geography

A view through the Boca do Algar (Mouth of the Cavern)

Stalactites in the Algar do Carvão

Terceira is the site of four large volcanoes (Pico Alto, Santa Bárbara, 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. Algar do Carvão is situated at 583 metres (1,913 ft) above sea level.^[1]

The 40.5 hectares (4,360,000 sq ft) extent was classified as a Regional National Monument (Portuguese: Monumento Natural Regional) due to its peculiar volcanological characteristics, in addition to its environmental ecosystem.^[1] The mouth of the Algar consists of a 45 metres (148 ft) vertical passage to the interior, that reaches a ramp of debris and gravel.^[1] From here there is another decline to the clear waters of the interior pool, approximately 90 metres (300 ft) from the level surface.^[1] The pool is supported by rainwater, and can reach as deep as 15 metres (49 ft) depth or become dry in summer months, owing to little or no precipitation.^[1]

The cave itself is remarkable for the unique mineralogical characteristics of its silicate stalactites.^[1]

Biome

The Algar is populated by a rich plant tapestry, that covers the mouth of the cone structure, including various endemic species. Further, there are several invertebrate species that make the cavern their homes, such as the cavernous spider Turinyphia cavernicola and other species of Troglofauna, like the centipede Lithobius obscurus azorae, the springtail Pseudosinella ashmoleorum and ground beetle Trechus terceiranus.^[1] Finally, there is a distinct presence of various moss, including those on the Red Data Book of European Bryophytes (ECCB), like the Alophosia azorica and Calypogeia azorica, among others.^[1]

References

Notes

1 2 3 4 5 6 7 8 9 Paulo Barcelos/SIARAM (September 2010)

Sources

Barcelos, Paulo (September 2010), "Algara do Carvão", SIARAM Sentir e Interpretar o Ambiente dos Açores (PDF) (in Portuguese), Horta (Azores), Portugal: SRAM Secretaria Regional do Ambiente e do Mar

Angra do Heroísmo

Civil parishes	Altares Cinco Ribeiras Doze Ribeiras Feteira Nossa Senhora da Conceição Porto Judeu Posto Santo Raminho Ribeirinha Santa Bárbara Santa Luzia São Bartolomeu de Regatos São Bento São Mateus da Calheta São Pedro Sé Serreta Terra Chã Vila de São Sebastião

Natural landmarks	Algar do Carvão Bay of Angra Bay of Pontas Bay of Salga Bay of Refugo Cabras Islets Furna de Água Galerias da Feteira Gruta Brisa Azul Gruta das Agulhas Gruta das Cinco Ribeiras Gruta das Mercês Gruta do Zé Grande Gruta dos Ratões Lagoa do Negro Mata da Serreta Monte Brasil Parque de Campismo das Cinco Ribeiras Ponta do Queimado Porto das Cinco Ribeiras Prainha Serra da Ribeirinha Serra de Santa Bárbara Serra do Morião ou da Nasce Água Zona Balnear do Negrito

Man-made landmarks	Bettencourt Palace Cais da Alfândega Cais da Silveira Castle of Moinhos Cemetery of Anchors Church of São Mateus da Calheta Convent of São Gonçalo Duke of Terceira Garden Fort of the Açougue Fort of the Cavalas Fort of the Church of São Mateus da Calheta Fort of Greta Fort of Má Ferramenta Fort of the Maré Fort of Negrito Fort of Santo António do Monte Brasil Fort of São João Fort of São João Baptista Forte das Caninas Forte das Cinco Ribeiras Forte da Salga Forte de Santa Catarina das Mós Forte de Santo António Forte de São Fernando Forte de São Francisco Forte de São Sebastião Forte do Terreiro Forte do Zimbreiro Fortress of São Mateus da Calheta Reducto da Salga Miradouro da Amoreira Miradouro da Ponta do Queimado Miradouro da Serreta Miradouro das Veredas Miradouro do Pico das Cruzinhas Miradouro do Pico Matias Simão Municipal Palace/Hall of Angra do Heroísmo Parque Arqueológico Subaquático da Baía de Angra do Heroísmo Parque de Campismo das Cinco Ribeiras Parque Municipal do Relvão (Angra do Heroísmo) Porto das Cinco Ribeiras Redoubt of Dois Paus Redoubt of Três Paus Manor of Madre de Deus Sé Cathedral of Angra do Heroísmo

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