Azores - São Miguel - 4 - Dos Picos volcanic complex - Gruta do Carvão

Par Bernard Duyck

Located in the central area of the Volcanic Complex dos Picos, characterized by 200 cinder cones and a fissural volcanism, Gruta do Carvão is the largest lava tube on São Miguel, with a total length of 1,250 meters, in two separate sections.

This tunnel extends within a basalt flow, north-south, and reaching the sea west of Ponta Delgada.

Azores - São Miguel - Gruta do Carvão - photo page Facebook / Gruta do Carvão

Map of volcanic areas of São Miguel - the dos Picos Volcanic Complex is colored gray with the position of the various caves / lava tubes (black triangles and points)

Its average height is 2-3 meters, with passages reaching more than 5 meters. Its width varies significantly, with a maximum above 10 meters, particularly at the intersection of several branches.

A stretch of 200 meters is characterized by the superposition of two tunnels having sinkholes. In some sections, runoff waters deposited sediment, with an average height of one meter.

Azores - São Miguel - Gruta do Carvão - photo Diogo Caetano / Amigos dos Açores - amigosdosacores@amigosdosacores.pt

Azores - São Miguel - Gruta do Carvão - photo page Facebook / Gruta do Carvão

Lava stalactites hang from the ceiling, sometimes covered with a whitish hue brought by runoff. The walls have "bolhas de gás", bubbles that have burst under the pressure of gas.

Azores - São Miguel - Gruta do Carvão - photo Diogo Caetano / Amigos dos Açores - amigosdosacores@amigosdosacores.pt

Azores - São Miguel - Gruta do Carvão - photo Guardar foto - Siaram

Basaltic lava is oxidized, giving it a reddish-orange hues along the cracks and areas of infiltration.

Azores - São Miguel - Gruta do Carvão: color of oxidized basalt - azoresphotos.blogspot.be

The age of this lava tube is between 5000 and 12000 years according to Carbon 14 dating and according to the analysis of deposits of pyroclastic material (ash and lapilli), possibly emitted by the volcano Sete Cidades of the Fogo, covering this cave.

Sources :

- Amigos dos Açores - associaçoa ecologica -link

- Gruta do Carvão - Paim - link

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