Historical eruptions of Pico have occurred from vents on its flanks rather than the summit crater. In 1562–64, an eruption on the southeast flank produced lava flows which reached the sea. Another flank eruption in 1718 also produced flows which reached the coast. The most recent eruption occurred in December 1718.

On 29 September 2009 there were reports from local news sources that indicated that a fumarole existing at the pinnacle of the mountain (Piquinho) began emitting volcanic gas. The region’s seismic and volcanological monitoring centre (Portuguese:CIVISA Centro de Informação e Vigilância Sismovulcânica dos Açores) indicated that the phenomenon occurred in the early morning, turning intense and visible in various points throughout the island and from Faial. Although the event resulted from exceptional meteorological conditions and was visible in the Central Group, there was no liberation of anomalous volcanic gases and all other parameters fell within norms.

Mount Pico is part of the Madalena Volcanic Complex, one of three volcanological units that comprise the island of Pico, associated with three historic eruptions in 1562, 1718 and 1720. Current morphology suggests an age dating to the Holocene age, confirmed by radiocarbon dates younger than 6000 years. Structurally, this complex can be subdivided into two other sections: the Pico Volcano and the East Fissural Zone.

Pico is a stratovolcano, with a pit crater on its summit. Pico Alto the round crater about 500 meters (1,600 ft) in diameter and 30 meters deep tops the volcano, with Piquinho (Pico Pequeno) a small volcanic cone rising 70 meters within it to form the true summit. Meanwhile, the East Fissural Zone comprises several alignments of Hawaiian/Strombolian scoria cones and associated lava flows, which overflowed many of the cliffs, cut in older units and originated lava deltas (Portuguese: fajãs).

The tectonic structure is characterized by two fault systems. The main WNW-ESE structures are the dextral faults of Laoga do Capitão and Topo, that merge to the east, forming a narrow shallow graben. To the west, the graben is completely covered by the Pico stratovolcano occurring less than 10,000 years ago, and infilled by lava flows and cones of the Eastern Fissural zone, that includes many of the volcanic alignments and scarps. The second fault zone, running NNW-SSE, are markedly less in number and includes normal left lateral, oblique slip faults responsible for the main volcanic eruptions: the Lomba de Fogo-São João fault (basis of the 1718 eruption)and the Santo António volcanic alignment.

On top of Pico (Piquinho) there is an area of permanent degasification characterized by the emission of water vapour at a temperature of between 50ºC to 75°C. In addition, other vents also exist between 1,500 metres (4,900 ft) and 2,000 metres (6,600 ft) above sea level, as well as diffuse degasification along the graben between the Lagoa do Capitão and Topo faults. There is also a carbon dioxide-rich spring in the locality of Silveira (along the southern coast of Lajes do Pico, formed in the base of Pico.

Hiking trails are available and the ascent to the summit can be made in around two to four hours from the trailhead for fit persons depending on weather which can be quite treacherous especially in winter months.

These debris fields exist in all the archipelago of the Azores, but are concentrated on the island of São Jorge .^[2] The island is volcanic in character with steep cliffs running down to the coast, and where fajãs extend into the sea caused by the collapse of these cliffs. The long fetch of the Azores is a high-energy wave climate, and the steep submarine slopes and absence of shallow shelves produce localized patterns of wave shoaling, refraction and diffraction: especially during storms.^[1] This leads to the fragmentation of the coast into a number of dynamic cells whose sediment alongshore is limited by impermeable boundaries.

There are fajãs on both sides of the island: along the southern coast are the notable fajãs of Velas, Vimes, Bodes, Além, São João, Cardoso and Alabaçal, while in the north there are a succession of smaller fajãs (resulting from the collapse of lands cut by small ravines). The exception to this are the Fajãs of Caldeira do Santo Cristo (with an underwater cave and an open lagoon); the Fajã dos Cubres (with closed lagoon ecosystem) crystalline lake; the Fajã do Ouvidor, a dendritic fajã extending into the sea, used by fishers. Although many of these fajãs have been abandoned, the settlements which include abandoned homes, mills and fountains continue to be iconic outposts on hiking trails.

The fajãs are fertile and, historically, used in the cultivation of yams, maize and vegetables, although coffee, vineyards and tropical fruits were also grown. Here, several fajãs are scattered along the northern and southern coast, including the fajãs of Santo Cristo and Cubres, with their distinctive saltwater lagoons. One of the more unique harvests happens at Fajã of Caldeira do Santo Cristo, where the lagoon supports cockles: this makes Santo Cristo a popular destination for the unique gastronomic cuisine in the Azores.

The photo is from 1900, but the American whaling ships already ran the seas since at least the XVIII sec. By passing the islands of the Azores and Cape Verde, often recruited men who were enjoying the adventure of opportunity, another life, to get to America. Some died at sea, a deserted before reaching the New World, the other Azorean whalers have become major, returned to their land, and realized that the islands were ships in the middle of the Atlantic high, and the canoes could be launched from land, was born by wheel the second half of the XIX sec whaling Açoreana.