Pica gap is a segment in the
Central Volcanic Zone of
Chile where volcanic activity is absent.[1] It is named after the Altos de Pica region.[2]
This segment is 100 kilometres (62 mi) long and extends between the volcanoes
Isluga in the north and
Irruputuncu in the south.[1] Volcanoes in the gap are old,
Miocene to
Pliocene in age and are heavily eroded. Examples include
Cerro Napa [
sv], Cerro Cariquima and Cerro Tatjachura.[3]
At the latitude of the Pica gap, an underwater rise known as the
Iquique rise is
subducted in the
Peru-Chile Trench. It is unclear if the subduction of this rise is the cause for the lack of recent volcanism in the Pica gap.[3] The lack of volcanism in the Pica gap appears to be due to unfavourable mantle flow patterns, which prevent the ascent of magma.[4]
Geologically, the Pica gap lies between two
crustal domains which are defined by their divergent
leadisotope ratios,[5] the northerly
Arequipa-Antofalla block of
Proterozoic age and the southern
Chileniaterrane of
Paleozoic age.[6] Other phenomena which coincide with the Pica gap are the absence of tectonic
horsts west of the Andes,[2] an area where a zone of high
electrical conductivity in the deep crust beneath the
forearc does not extend to the actual
volcanic arc (and thus may reflect the absence of molten magma),[7] the lack of a low
seismic velocity zone in the crust,[8] a symmetry plane of the
Andes, the
Salar de Uyuni basin behind the arc and the location of the actual bend in the Andes that is usually placed at the
Arica Bend. These phenomena may be unrelated to the Pica gap, however.[3]
^
abcPritchard, M. E.; Henderson, S. T.; Jay, J. A.; Soler, V.; Krzesni, D. A.; Button, N. E.; Welch, M. D.; Semple, A. G.; Glass, B. (2014-06-01). "Reconnaissance earthquake studies at nine volcanic areas of the central Andes with coincident satellite thermal and InSAR observations". Journal of Volcanology and Geothermal Research. 280: 96.
doi:
10.1016/j.jvolgeores.2014.05.004.
^Araya Vargas, J.; Sanhueza, J.; Yáñez, G. (November 2021). "The Role of Temperature in the Along‐Margin Distribution of Volcanism and Seismicity in Subduction Zones: Insights From 3‐D Thermomechanical Modeling of the Central Andean Margin". Tectonics. 40 (11).
doi:
10.1029/2021TC006879.
^de Silva, Shanaka L.; Davidson, Jon P.; Croudace, Ian W.; Escobar, Angel (1993). "Volcanological and petrological evolution of Volcan Tata Sabaya, SW Bolivia". Journal of Volcanology and Geothermal Research. 55 (3–4): 309.
doi:
10.1016/0377-0273(93)90043-q.
^Echternacht, Friedrich; Tauber, Sebastian; Eisel, Markus; Brasse, Heinrich; Schwarz, Gerhard; Haak, Volker (1997). "Electromagnetic study of the active continental margin in northern Chile". Physics of the Earth and Planetary Interiors. 102 (1–2): 85.
doi:
10.1016/s0031-9201(96)03261-x.