Algar do Carvão
Encyclopedia
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
.
, 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.
Terceira Island
Referred to as the “Ilha Lilás” , Terceira is an island in the Azores archipelago, in the middle of the North Atlantic Ocean. It is one of the larger islands of the archipelago, with a population of 56,000 inhabitants in an area of approximately 396.75 km²...
in the Azores
Azores
The Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the...
. It lies within the municipality of Angra do Heroísmo
Angra do Heroísmo
Angra do Heroísmo , locally referred to as Angra, is a municipality and city on the island of Terceira, within the Portuguese autonomous region of the Azores. The municipal area has a population of 35,581 and an area of . Along with Praia da Vitória to the north, it is one of two municipal...
in the parish of Porto Judeu
Porto Judeu
Porto Judeu, which means "Jewish Port" in Portuguese, is a parish in the municipality of Angra do Heroísmo on the island of Terceira in the Azores. The population in 2001 was 2425, its population density was 80.11/km², and the land area is 30.27 km²....
.
Toponymy
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.Geography
Terceira is the site of four large volcanoes (Pico Alto, Santa BarbaraSanta Bárbara (Angra do Heroísmo)
Santa Bárbara is a parish in the municipality of Angra do Heroísmo on the island of Terceira in the Azores. The population in 2001 was 1366, its population density was 83.29/km², and the land area is ....
, 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
Mineralogy
Mineralogy is the study of chemistry, crystal structure, and physical properties of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.-History:Early writing...
characteristics of its silicate
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
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.