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 (at Piquinho) there is an area of permanent degasification characterized by the emission of water vapour at a temperature of between 50 °C to 75 °C. In addition, other vents also exist between and 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. Observatory Mount Pico's long topographic isolation and low altitude marine boundary layer makes it an ideal place for the study of aerosol particles. In 1998, an observatory station (PICO-NARE) was placed on the summit caldera at altitude. The observatory was founded and is operated by the University of the Azores, with the cooperation of the Michigan Technological University, the Institute of Arctic and Alpine Research, and the University of Colorado Boulder, along with other international scientists, and is designed to study the impacts that air pollutants emitted in North America and Europe have on the atmosphere over the North Atlantic Ocean. See also List of European ultra prominent peaks Mons Pico References Notes Sources External links Photographic chronicle of a climb to the top of the Pico volcano. Pico - A Ilha Montanha Atlantica - Flickr Group Photo Gallery Recent pictures of a climb to the top of Pico volcano. Mountains of Portugal Extreme points of Portugal Stratovolcanoes of Portugal Pico Island Two-thousanders of Portugal Geology of the Azores Highest points of countries Holocene stratovolcanoes