Sections

“Gruta do Carvão” presents various sections whose interconnections are either not known or not able to be made. Nowadays, only the “Rua do Paim” section (the farther north) can be visited but it is expected that in a near future also the “Rua de Lisboa” section becomes open to public visitation. In the following texts we briefly describe each known section of the “Gruta do Carvão” cave system. "Rua do Paim" Section This section is the uppermost accessible part of the tube system and has a total length of 880,2 meters. It has a North – South orientation from the “Saúde” street, in Arrifes to the water reservoirs of the city of Ponta Delgada located in Paim street. Above the tube in its path we find namely, farmlands, greenhouses and some residential buildings. The lava tube is 6,4 m high and has an average width of 5,8 m. From the surface to the roof of the cave the depth varies between 2 and 3 m. In this section it´s noticeable the superposition of two individual tunnels, these tunnels prolong one over each other for approximately 200m. At some points these two tunnels are connected by either primary flow structures or secondary holes due to partial collapse events. It was built a visitors centre and a concrete tunnel that allowed the access to the interior of the lava tube. Before that the only way of entering the tube was through a private property in "Paim" street. In 1996, during the construction works of “2ª Circular” Highway, a new part of this section (towards North) with an extension of about 550 m was first mapped. More recently, in September 2007 during the Espeleo – Arcanjo expedition, another previously unknown 130 m of the tube system were mapped.

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View of the interior of the "Gruta do Carvão" - "Paim" Section

Gruta da Rua do Paim

Topography of the "Rua do Paim" lava tube, the northernmost section of the "Gruta do Carvão" cave system (in “Catálogo das Cavidades Vulcânicas dos Açores”)

“Rua de Lisboa, Secadores de Tabaco” Section

This section is 701,8 meters long and for most of its extension it is comprised by a single tunnel with a NNW-SSE orientation that goes from Lisboa street (near the tobacco drying facilities of “Tabaco Micaelense”) until the intersection between Pintor Domingos Rebelo street (former Carvão street) and Antero de Quental avenue.

The medium height goes from 2 to 3 meters, though in some places it exceeds the 5 m and the medium width is 5 m reaching more than 10 m wide in the “Bairro da Misericórdia” area, where the two tunnels merge.

At some places of this section, rock walls have been built in order to reinforce the natural walls. These walls and remnants of an electric installation prove the human utilisation of this cave in the past. These walls can be best seen under the tobacco company buildings. This zone was used in the past as a materials deposit of the factory so it´s in some way altered and artificialized.

Recently, despite being crossed underneath by the lava tube, some terrains at surface have been urbanized (namely between “Bairro da Misericórdia” area and Carvão Elementary School).

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View of the interior of the "Gruta do Carvão"

Gruta do Carvão

Topography of the  "Rua de Lisboa , Secadores de Tabaco"  section of the "Gruta do Carvão" (in “Catálogo das Cavidades Vulcânicas dos Açores”)

“Rua do João do Rego” Section

This part of the tube was recently rediscovered, in October 2000 during the sanitation works in “João do Rego” street, carried out by municipal services of the city council of Ponta Delgada.

This section consists of two fairly parallel branches with a NW-SE orientation that develop mainly under housing properties in the “João do Rego” street and the sugar factory “SINAGA” and also reaches some houses in the “1ª Rua of Santa Clara”. The oriental tube has a length of 100 m while the western tube is approximately 200 m long. These two branches meet below “João do Rego” street and continue as one only tube for a further 40 m with a N-S orientation.

In this section it´s possible to walk in almost all of its extension as it has a medium height of 3 m, reaching up to 6 m in some places, as for the maximum width it tops 13 m in the western branch. The roof of the tube is around 2 to 3 m below the surface.

Environmentally speaking, today this section of the “Gruta do Carvão” is considerably degraded and in a bad state of conservation, mostly due to the fact that it was used as a domestic waste disposal by the neighborhood and because it was structurally affected by the constructions in the surrounding area.

GRUTA RUA JOÃO DE REGO 27-10-2000

View of the interior of the "Gruta do Carvão" –  "Rua João do Rego" section, during an expedition in October 2000

Gruta da Rua João do Rego

Topography of the "Rua João do Rego" tube, the southernmost section of the "Gruta do Carvão" cave system (in “Catálogo das Cavidades Vulcânicas dos Açores”)

“Rua José Bensaúde” Section

This section was rediscovered in the beginning of 1970 while the José Bensaúde street was being paved. This volcanic pit is the most downstream section of the “Gruta do Carvão” cave system.

The José Bensaúde pit is very diminished, it´s 42,7 m long, 5 m high and 7,5 m wide and has a vaulted ceiling. The general orientation of the pit is E-W.

It´s very likely that this section possesses a connection to the sea as the level of still water in there varies (up and down) depending on the sea level.

In February 1999, members of the “Grupo de Trabalho de Espeleologia dos Amigos dos Açores” were able to visit this section as it was accessible due to some major road works. However, it was not possible to proceed beyond the entrance because it was obstructed by fluvial sediments.~

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"José Bensaúde" pit entrance, during the sanitation works on the street with the same name, in 1999.

Gruta da Rua José Bensaúde

Topography of the "Rua José Bensaúde" volcanic pit (in “Catálogo das Cavidades Vulcânicas dos Açores”)