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Sierra de Gredos
The Sierra de Gredos is a mountain range in central Spain that spans the provinces of Ávila, Salamanca, Cáceres, Madrid, and Toledo. It is part of the much larger Central System of mountain ranges. Its highest point is Pico Almanzor, at 2,592 metres and it has been declared a natural park by the Autonomous Community of Castile and León. The Sierra de Gredos is one of the most extensive mountain ranges of the Central System, and it comprise 5 river valleys: the Alto Tormes, the Alto Alberche, the Tiétar Oriental, the Tiétar Occidental y la Vera, and the Valle del Ambroz. The first known inhabitants were the Vettones, a pre-Roman Celtic people. The central part of the range encomprises the Sierra de Gredos Regional Park.
==Geology==
The Sierra de Gredos comprises mainly granite, which is a common type of intrusive, felsic, igneous rock which is granular and phaneritic in texture. This rock consists mainly of quartz, mica, and feldspar. In some Gredos rocks the feldspar crystals are especially large, attaining a size of several centimeters in some cases. There is also some granodiorite and outcrops of metamorphic rocks.
During a large part of the Paleozoic Era, from 600 to 350 million years ago, the whole area was covered by the Tethys Ocean where horizontal layers or strata of sediments accumulated due to the process of erosion in the unflooded regions. These sediments were fractured and folded due to the actions of the Variscan Orogeny and extensive areas emerged from the sea. At the end of the Paleozoic molten magma rose up which turned into granite as it cooled. Erosion continued for a long time until between 40 and 2 million years ago, when another convulsion, known as the Alpine Orogeny, created the mountains that today comprise the Central System. The tectonic style of the Sierra de Gredos is the so-called Germanic style, i.e. with large upraised fault blocks, known as horst, bounded by graben.
The Sierra de Gredos is divided into three sectors: the Eastern sector up to the Puerto del Pico fault, the Central sector up to the Puerto de Tornavacas fault, and the Western sector which is the Sierra de Béjar.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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