All of the nine islands and the few islets that make up the archipelago
are of volcanic origin. The volcanic activity that created these
islands ranges from effusive eruptions, characterized by a steady outpouring
of lava, to explosive events, with violent fragmentation of
lava. The oldest volcanic rocks are dated at 8.12±0.85Ma and can be
observed in the Santa Maria Island (Abdel-Monen et al., 1975). Since
the settlement of the archipelago,which took place in the 15th century,