Very few places in the world allow you to explore and go inside a volcano. One of these places is the Algar do Carvão, located in the Azorean island of Terceira. The name Algar do Carvão means “coal pit” because the cave walls are formed from dark black lava.
To enter you go down the volcano chimney that is lava free today, uncommon in most volcanoes, and a tunnel and staircases offer access to the caves below. At the bottom there is a crystal clear lake formed by rainwater, with unique stalactites and stalagmites.
The Algar do Carvão is, in fact, one of the few volcanoes in the world you can visit and the only one in which visitors can explore a volcanic chimney and secondary magma chambers. The volcanic eruption that took place at Algar do Carvão 3,200 years ago originated into volcanic rock highly rich in silica. Then, a second eruption, 2,000 years ago happened in the same place but with basaltic lava that formed several magmatic chambers.
Thanks to this fluid lava the chimney and the magma chambers were left empty when it all settled down. Algar do Carvão is now the only place on earth where you can see these two structures, the chimney and chambers without being cooked alive. What stands out as unique in the world is the stalactites and stalagmites formed by amorphous silica – Alvar do Carvão actually has the biggest concentration in one place.
Tours and the general maintenance of the volcano cave is in charge of local association “Os Montanheiros.” The first group of Montanheiros went to the volcano interior Montanheiros in 1963 and in 1968 they led the first visitors. Visits take place all summer and have to be scheduled in advance in the winter. They also organize visits to the Gruta do Natal, on Terceira.