Azores

Sao Miguel - Geological Highlights

Fogo Caldeira: The main edifice was built as the result of the accumulation of lava flows, domes and pyroclasts, mainly of trachytic nature, until the last 40'000 year old main eruption. A major caldera forming eruption was recognized between 47'000 and 2'6000 years ago. The products of the last 40'000 years of activity can be observed in the sea cliffs and the main valleys. Thick sequences of pyroclastic deposits show the importance of explosive activity during this period that produced many pumice fall deposits, some of plinian scale, pyroclastic flows, surges and mudflows. This activity, mainly intracalderic, was intercalated with more basic effusive or moderately explosive events on the flanks of the volcano. In the last 15'000 years about 20 eruptions took place, including another caldera-forming eruption. The well known Fogo. A plinian deposit is the result of one of the 7 explosive trachytic eruptions that marked the activity of Fogo in the last 5000 years, including the historical events of 1563 AD and 1564 AD.