The outer caldera dates from between 30,000 and 45,000 years ago, and comprises an area 4 kilometres (2.5 mi) wide and 13 kilometres (8.1 mi) long outer caldera (corresponding to the Água de Pau Massif).
The inner caldera, which is 2.5 kilometres (1.6 mi) wide and 3 kilometres (1.9 mi) long was formed about 15,000 years ago.
It is the younger inner caldera that is partially filled by the crater lake Lagoa do Fogo.

Until about 5000 years ago, activity in the caldera created several lava domes on the northern and western flanks.

Some of the cinder cones on these flanks are marked by radial and concentric fissures and have been active within the last 5000 years.
The region has been marked by five large eruptions, which included sub aerial events 1563, 1564 and 1652.
The 1563 eruption, for example was characterized by a hydromagnetic event in the interior of the caldera, which was followed four days later by an effusive eruption, while the 1564 was an explosive hydromagmatic event.

Owing to the existence of hot springs along the northwest flank, particular in the so name Caldeiras da Ribeira Grande and Caldeira Velha, the region has been used in the generation of geothermal energy or as therapeutic tourist spas.
The outer caldera dates from between 30,000 and 45,000 years ago, and comprises an area 4 kilometres (2.5 mi) wide and 13 kilometres (8.1 mi) long outer caldera (corresponding to the Água de Pau Massif). The inner caldera, which is 2.5 kilometres (1.6 mi) wide and 3 kilometres (1.9 mi) long was formed about 15,000 years ago. It is the younger inner caldera that is partially filled by the crater lake Lagoa do Fogo.
Until about 5000 years ago, activity in the caldera created several lava domes on the northern and western flanks.
Some of the cinder cones on these flanks are marked by radial and concentric fissures and have been active within the last 5000 years. The region has been marked by five large eruptions, which included sub aerial events 1563, 1564 and 1652. The 1563 eruption, for example was characterized by a hydromagnetic event in the interior of the caldera, which was followed four days later by an effusive eruption, while the 1564 was an explosive hydromagmatic event.
Owing to the existence of hot springs along the northwest flank, particular in the so name Caldeiras da Ribeira Grande and Caldeira Velha, the region has been used in the generation of geothermal energy or as therapeutic tourist spas.
Água de Pau Massif