Pico Island

Panorama of the westernmost part of the Island, and Faial Island at a distance

View of the stratovolcano near Pico Wine Museum

High altitude area of the island, showing cloud cover adjacent to the summit

The two islets at the entrance to Madalena harbor, formed from a submerged crater

The island is 17.5 km south of São Jorge and just 7 km east of Faial, in the Central Group of islands, an area that is colloquially known as o Triangulo (The Triangle). Pico is 46 kilometers long, and at its maximum extent about 16 kilometers wide, rising from its center to the west in the summit of the stratovolcano of Pico; making it the second largest of the Azores islands. Along the central plain of volcano cones to the eastern coast, the landscape is pitted with the remnants of craters and lake-filled cones, and dominated by the ancient volcano of Topo. Geomorphologically, the island is composed of three units:

• Topo Volcano - Located on the southeastern coast, it corresponds to an ancient volcano destroyed by erosion and landslides;
• Plain of Achada - Extending from Topo to the stratovolcano, the Achada Plain is an axial zone comprising spatter and lava cones along a mountainous ridge filled with lake-filled craters, dense scrub and forests. Cones in this region are oriented along a west-northwest and south-southeast axis along a path east to west between the other volcanic structures;
• Pico Volcano - It occupies the western portion of the island, and corresponds to the central volcano with a 2,341-metre (7,680 ft) altitude. Along its flanks are diverse lava and spatter cones that are formed along radial fractures and faults.

Generally, the island of Pico's tectonic structures are oriented along a west-northwest to east-southeast and a northeast to southwest axis. The main axis controls the main structures, especially the main mountain of Pico, while the secondary axises affect the radial fractures and faults along the central plain and eastern volcano.

Similar to the geomorphological structures described above, the volcanic landforms have been identified by Madeira (1998) in the following units:

• Volcanic Complex of Lajes - pertains to the oldest volcanic structures, comprising volcanoes, lavas and debris that are between 35 and 300,000 thousand years old; it makes up the structures of the eastern part of the island, including the ancient volcano of Topo.
• Volcanic Complex of Calheta de Nesquim - dating to about 230,000 thousand years ago, this is a fissural zone of cones and basaltic lavas, associated with the Achada Plain, and the many faults along the central plateau of the island.
• Volcanic Complex of Madalena - the most recent volcanic complex, with both geological and historical eruptions; it includes the basaltic stratovolcano of Pico, but also many of the cones, faults and lava fields that circle the 2,351 meter summit.

The last volcanic eruption (which is debatable) occurred in 1963, in a small submarine eruption off the northwest coast (north of Cachorro in Santa Luzia). Prior to this, major volcanic activity was evident in lava fields generated in only the areas of Prainha (1562–64), Santa Luzia (1718), São João (1718) and Silveira (1720). The paths of the lava flows are still visible; those in the 16th century and 1718 were particularly substantial, extending for over 10 km. Today, the only visible evidence of active volcanism appears on the summit of Pico, in the base and interior of the Piqueninho (the mini-peak on the summit); there are irregular emissions from cracks in this zone. Additionally, there are emissions on the eastern flanks between 1500 and 2000 meters altitude. There have also been found areas of de-gasification along the fault associated with the Lagoa do Capitão and another in the Topo Volcano, as well as a spring rich in CO2 in the area of Silveira.

Pico, much like the other islands, is susceptible to seismic events, although their epicenters have primarily been localized in the Faial-Pico or Pico-São Jorge Channels. The strongest earthquake registered in the last 30 years occurred on July 9, 1998, and had its epicenter 5 kilometers northeast of Ponta da Ribeirinha, on the island of Faial, reaching a 5.8 magnitude. It was felt on Pico, with a maximum intensity level of VII on the Mercalli scale; some homes were damaged and possessions were buffeted. Other violent earthquakes which have affected the island include: the 1957-58 seismic events associated with the eruption of the Capelinhos volcano (on Faial), the February 1964 earthquake on the island of São Jorge, and the 1926 earthquake, whose epicenter was registered in the Faial-Pico Channel.

Azores junipers showing their response to the humid climate in the central reserve of the island, near Lagoa do Capitão (Captain's Lagoon)

Due to its topographic variation, the island has dramatic temperature and precipitation fluctuations.

At lower elevations, where most of the population resides, Pico has a humid subtropical climate (Köppen: Cfa) with very mild, rainy winters and warm, noticeably drier summers, although generally not dry enough to be classified as Mediterranean. It has an average temperature of 17.5–18 °C (63.5–64.4 °F) and around 1,000 mm (39 in) of precipitation falls each year though it can reach values as high as 2,000 mm (79 in) on the northeast coast (mainly on Prainha and Santo Amaro).[9] Because of its high relative humidity (around 80%), summers can feel slightly warmer than they really are.[10][11]

At higher elevations, temperatures are cooler and precipitation increases, it therefore transitions into an oceanic climate, average relative humidity stays around 90%.[10] Places such as the Caiado and Paul lagoons receive, respectively, 4,698 and 3,357 millimetres (185.0 and 132.2 in)[12] of precipitation each year though Mount Pico is recognized as receiving the largest annual rainfall in Portugal (over 6,250 mm (246 in) per year at the base of the volcano).

As altitude reaches 1,500 metres (4,900 ft) and exceeds the planetary boundary layer, both precipitation and humidity levels decrease reaching the top of the volcano which averages only around 500 millimetres (20 in) of precipitation. Temperatures at the peak of the stratovolcano (2,300 metres (7,500 ft) a.s.l.) average 4 °C (39 °F) and snow can be occasionally seen in the cooler months, one of the few places in the archipelago where this phenomenon is possible.[9] The climate at this altitude is now subpolar oceanic (Cfc).

The main settlements are Madalena, São Roque do Pico and Lajes do Pico; the total population is 15,761 inhabitants (as of 2007).

• 
  The village of Madalena at the western base of Mount Pico, as seen from the Faial-Pico Channel
• 
  Lajes do Pico, along the south-central coast, with Mount Pico in the distance
• 
  The port and historic centre of the civil parish of São Roque, showing the whaling museum, and former rendering factory along the coast

• Scarth, Alwyn; Tanguy, Jean-Claude (2001), Volcanoes of Europe, Oxford University Press, p. 243, ISBN 0-19-521754-3
• Nunes, J.C. (1999), A actividade vulcânica na ilha do Pico do Plistocénio Superior ao Holocénio: Mecanismo eruptivo e hazard vulcânico. Tese de doutoramento no ramo de Geologia, especialidade de Vulcanologia, Ponta Delgada: University of the Azores, p. 357
• Madeira, José Eduardo de Oliveira (1998), Estudos de neotectónica nas ilhas do Faial, Pico e S. Jorge: uma contribuição para o conhecimento geodinâmico da junção tripla dos Açores. Tese de Doutoramento no ramo de Geologia, especialidade em Geodinâmica Interna, Lisbon: Faculty of Sciences, University of Lisbon, p. 428
• Madeira, José Eduardo de Oliveira; António Brum da Silveira (October 2003), Active tectonics and first paleoseismological results in Faial, Pico and S. Jorge islands (Azores, Portugal), 5, 46, Lisbon: Annals of Geophysics, pp. 733–761
• Senos, M.L.; Gaspar, João Luís; Ferreira, Teresa; Cruz, L.; Nunes, J.C.; Pacheco, J. (1998), O terramoto do Faial de 9 de Julho de 1998, Proceedings do 1º Simpósio de Meterologia e Geofísica da AMPG, pp. 61–68