User:Thought22Potato/Central America Volcanic Arc

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The Central American Volcanic Arc (often abbreviated to CAVA) is a chain of volcanoes which extends parallel to the Pacific coastline of the Central American Isthmus, from Mexico to Panama. ''This volcanic arc, which has a length of 1,100 kilometers (680 mi) (Rose, 1999; Whattam, 2015) is formed by an active subduction zone, with the Cocos Plate subducting underneath the Caribbean Plate (Alvarez-Gomez 2008). Numerous volcanoes are spread throughout various Central American countries; many have been active in geologic past, some more so than others.''

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''The Cocos tectonic plate is along the western edge of Central America. The latter is along the western edge of the Caribbean tectonic plate and can be split into two distinct regimes (Alvarez-Gomez 2008). These regimes are demarcated roughly by the Costa Rican-Nicaraguan border and can be differentiated by the different tectonic histories of each respective area. The southern portion is part of a magmatic arc, while the northern one is associated with several active margins (Alvarez-Gomez 2008). Different types of faults also exist within each regime (Alvarez-Gomez 2008) and further serve to differentiate the northern and southern regions’ geologic and tectonic histories from one another.''

''This Caribbean-Cocos tectonic plate interaction can further explain the volcanism and geologic history of the region. While previous literature has shown a wide range of ages for the subduction of the Cocos plate (Abratis 1998, DeBoer et al. 1995, Grafe 1998, Colins et al. 1995, Lonsdale and Klitgord 1978), it is now believed that this subduction began between 2 Ma and 3 Ma (MacMillen 2004; Morel 2012), though the area has been geologically active since at least 12 Ma, as evidenced by plate and plate boundary movements, as well as scarp subduction (MacMillen 2004) in the area. A gap in volcanism in Central America between 12 Ma and 5 Ma (MacMillen et al 2004; Morel 2012) is understood to have occurred as well.''

''Furthermore, the subduction of the Cocos tectonic plate itself is not thought to be what caused some of the changes in volcanism associated with the Central American Volcanic Arc; while the subduction of the Cocos Ridge is a continual event that has influenced volcanism in Central America, the subduction of the Coiba Ridge—a microplate in the region-- is thought to be the triggering event (MacMillen 2004) that instigated changes in volcanic activity in the geologic past. In short, the interaction of numerous tectonic plates—namely the Cocos, Caribbean, North American, and Coiba (Alvarez-Gomez 2008; MacMillen 2004; Morell 2012) plates—over the past several million years has helped facilitate the continual existence of the Central American Volcanic Arc, influencing the tectonic and broad geologic history of the area.''

''The Central American Volcanic Arc consists of hundreds of volcanic formations, including stratovolcanoes, composite volcanos, calderas, and lava domes. From a depositional standpoint, ash falls, ash flows, and deposits of tephra are prevalent throughout the region (Rose, 1999; Williams, 1983). Carbon and argon isotope dating has been used to date these deposits to the Quaternary (Rose, 1999), and it is suspected that several of these volcanos have been sporadically active for much of the past 200,000 years (Rose, 1999).''

''Some volcanos in the area have even produced large explosive eruptions in the recent past, including the October 25, 1902, eruption of the Santa Maria volcano in Guatemala (Williams, 1983). This Plinian eruption spewed upwards of twenty cubic kilometers of ash almost thirty kilometers into the sky (Williams, 1983). Much of this ash was fine-grained, averaging less than 2 millimeters in size (Williams, 1983).''

''Similarly, Cerro Negro, a 250-meter-tall volcano in northwest Nicaragua, erupted in 1971, 1992, and 1995 (Roggensack, 1997). The two latter eruptions, occurring in the 1990’s, had similar magmatic compositions to one another, both broadly basaltic. However, as the water and carbon dioxide contents of each eruption were different—with the earlier eruption having higher levels of carbon dioxide and water vapor, and the later eruption degassing many of its volatiles (Roggensack, 1997)-- markedly different styles of eruption occurred, with the 1992 eruption of Cerro Negro much more explosive than its 1995 counterpart.''

''Other volcanos in Central America include the Salvadorian Santa Ana, Izalco, and San Salvador volcanoes, the Nicaraguan Masaya volcano, and the Costa Rican Miravalles, Irazú, and Poás volcanoes (Melian, 2005). Many remain sporadically active to this day, and likely will continue to be active into the future, as geologic and tectonic processes continue to shape the region.''