The volcanoes at the west end of the archipelago are in general, taller, younger, have well developed calderas, and are mostly composed of tholeiitic basalt, while those on the east are shorter, older, lack calderas, and have a more diverse composition. It is the circumferential fissures which give rise to stacks of short lava flows. The Galápagos's shape is due to the pattern of radial and circumferential fissure, radial on the flanks, but circumferential near the caldera summits. The shape of these volcanoes is that of an "overturned soup bowl" as opposed to the "overturned saucer plate" of the Hawaiian Islands. Overall, the 9 active volcanoes in the archipelago have erupted 24 times between 19. The neighboring islands of Santiago and Fernandina last erupted in 19, respectively. For instance, Isabela Island includes 6 major volcanoes, Ecuador, Wolf, Darwin, Alcedo, Sierra Negraa and Cerro Azul, with most recent eruptions ranging from 1813 to 2008. Additional characteristics of the Galápagos Archipelago are closer volcano spacing, smaller volcano sizes, and larger calderas. Alcedo on Isabela Island had an uplift of greater than 90 cm, most recent eruption in 1993. Sierra Negra on Isabela Island experienced a 240 cm uplift between 19, most recent eruption in 2005, while Fernandina on Fernandina Island indicated an uplift of 90 cm, most recent eruption in 2009. Lacking a well-defined rift zone, the islands have a high rate of inflation prior to eruption. Fernandina and Isabela in particular are aligned along these weaknesses. The GSC caused structural weaknesses in this thin lithosphere leading to eruptions forming the Galápagos Platform. The Galápagos Archipelago is characterized by numerous contemporaneous volcanoes, some with plume magma sources, others from the asthenosphere, possibly due to the young and thin oceanic crust. Furthermore, the Galápagos Hotspot is at the northern boundary of the Pacific Large Low Shear Velocity Province while the Easter Hotspot is on the southern boundary. This spreading center truncates into the East Pacific Rise on the west and is bounded by the Cocos Ridge and Carnegie Ridge in the east. Besides the Galápagos Archipelago, other key tectonic features in the region include the Northern Galápagos Volcanic Province between the archipelago and the Galápagos Spreading Center (GSC) 200 km to the north at the boundary of the Nazca Plate and the Cocos Plate. The mantle plume beneath the east-ward moving Nazca Plate (51 km/myr) has given rise to a 3-kilometre-thick platform under the island chain and seamounts. Volcanism has been continuous on the Galápagos Islands for at least 20 million years, and perhaps even longer. Administratively, Galapagos constitutes one of the provinces of Ecuador, made up of three cantons that bear the names of its most populated islands, namely: San Cristóbal, Santa Cruz and Isabela. The older names remained in use in English-language publications, including Herman Melville's The Encantadas of 1854. The newly independent Republic of Ecuador took the islands from Spanish ownership in 1832, and subsequently gave them official Spanish names. These names were used in the authoritative navigation charts of the islands prepared during the Beagle survey under captain Robert FitzRoy, and in Darwin's popular book The Voyage of the Beagle. The first crude map of the islands was made in 1684 by the buccaneer Ambrose Cowley, who named the individual islands after some of his fellow pirates or after British royalty and noblemen. The group of islands was shown and named "Insulae de los Galopegos" (Islands of the Tortoises) in Abraham Ortelius's atlas published in 1570. De Berlanga eventually returned to the Spanish Empire and described the conditions of the islands and the animals that inhabited them. The first recorded visit to the islands happened by chance in 1535, when Fray Tomás de Berlanga, the Bishop of Panamá, was surprised with this undiscovered land during a voyage to Peru to arbitrate in a dispute between Francisco Pizarro and Diego de Almagro. The islands have a population of slightly over 25,000. The principal language on the islands is Spanish. The Galápagos Islands and their surrounding waters form the Galápagos Province of Ecuador, the Galápagos National Park, and the Galápagos Marine Reserve. His observations and collections contributed to the inception of Darwin's theory of evolution by means of natural selection. Located 906 km (563 mi) west of continental Ecuador, the islands are known for their large number of endemic species that were studied by Charles Darwin during the second voyage of HMS Beagle. The Galápagos Islands (official name: Archipiélago de Colón, other Spanish name: Las Islas Galápagos, Spanish pronunciation: , local pronunciation: ), part of the Republic of Ecuador, are an archipelago of volcanic islands distributed on either side of the equator in the Pacific Ocean surrounding the centre of the Western Hemisphere.
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