Description
The Sete Cidades volcano is situated on the extreme western portion of the island of São Miguel occupying an area of approximately 110 square kilometres (42 sq mi) and refers to a polygenetic volcano (Sete Cidades Massif) and caldera.[6] Its subaerial volume, of about 70 cubic kilometres (17 cu mi), has grown at an estimated rate of 0.02–0.03 cubic kilometres (0.0048–0.0072 cu mi) per century, beginning more than 210,000 years ago.[6] Presently, the interior of the structure is occupied by diverse volcanic structures and four lakes. It is almost circular caldera (5 kilometres (3.1 mi) in diameter and up to 400 metres (1,300 ft) high walls) formed through three phases of eruptions.[6] The last intra-calderan eruption occurred approximately 500 years A.D., resulting in the creation of the Caldeira Seca cone. At the base of the caldera, there exist six Holocene era pyroclastic cones. Further, a large group of pleistocene post-caldera trachytic lava domes, lava flows, and pyroclastic flow deposits have been discovered on the northwestern flanks of the massif.
The two crater lakes (Portuguese: Lagoas das Sete Cidades), 500 metres (1,600 ft) within the crater, are referred to by the color of the waters: blue, reflecting the sky (Portuguese: Lagoa Azul) and green, reflecting the ground (Portuguese: Lagoa Verde). According to legend, the differently colored lakes were created when a princess and her lover, a young shepherd, had to part from each other. The tears they shed at their farewell became the two lakes, with the water colored like their eyes.
