OCTOBER 16
Aconcagua
El sólo mérito de su altura, hacen del Aconcagua
una singularidad geológica digna de figurar en esta sección…. y es que se trata
de la montaña más alta de América…
No sé si esto es decir mucho o poco, porque
ni siquiera alcanza los 7.000 metros y, aunque he conocido gente absolutamente
normal que se ha pagado un viaje de agencia hasta la cumbre, no es menos cierto
que la montaña a veces da sus zarpazos, y se lleva por delante la vida quizás
no de montañeros o alpinistas, pero sí de aventureros. Para eso, no hacen falta
de hecho montañas tan altas.
The only merit of its height, makes the Aconcagua a worthy geological uniqueness to include in this section .... and yet it is the highest mountain in America ... I do not know if this is a much to say or not, since it does not even reaches 7,000 meters and, although I have known quite normal people who paid a travel agency to take them to the summit, the fact remains that the mountain sometimes shows its claws, and takes its life tributes…
Geologically the Aconcagua region is a key area to analyze the geological evolution of the Main Andes, which constitutes its peak area. Its high elevation does not correspond to an active volcano, but is the result of tectonic uplift of the range, controlled by the subduction occurring off the Pacific coast of Chile ...
Geológicamente la región del Aconcagua constituye
un área clave para analizar la evolución geológica de la cordillera Principal
de los Andes, de la que constituye su punto culminante. Su gran elevación no
corresponde a un edificio volcánico activo, sino que es el resultado del
levantamiento tectónico de la cordillera, controlado por la subducción que se
produce frente a la costa pacífica de Chile… y en la que interactúan las placas
de Nazca y Sudamérica.
En vuelo a Santiago, no es difícil ver el Aconcagua por la ventanilla. Es inconfundible. Una mole de roca andesítica, oscura, parcheada de manchas blancas de la nieve aferrada a su cumbre y a sus laderas. Laderas escarpadas y desnudas, descarnadas y recubiertas también de pedreras.
The geological description of the Aconcagua region has followed, since the nineteenth century, a swing of controversial explanations of its origin. The first field observations described the top of the hill like sandstone, limestone and gypsum, whose layered nature could not correspond with a volcano. However both volcanic Mount Aconcagua and La Ramada rocks were wrongly assigned to a current volcanic edifice when they are actually allochthonous deposits.
On January 20, 1835, a British merchant observed from the port of Valparaiso an erupting volcano and assumed that it was the Aconcagua. Just at that time Charles Darwin was walking through the port, to whom he told the story. Darwin had observed an eruption of Osorno volcano from the boat when they were heading north to Valparaiso. On that basis, the scientist repeated on several occasions, circles and publications that Aconcagua was an active volcano. His fame and prestige avoided questioning the claim until much later.
German Walter Schiller can be considered the greatest architect of knowledge of the geology of Aconcagua and although his greatest contributions date back to the early twentieth century, his Tectonic revolutionary ideas would not be fully accepted until past half century. His masterful work published in 1912: "The High Cordillera of San Juan and Mendoza and part of the province of San Juan," was misinterpreted and his conclusions were rejected. His remarks were reinterpreted, tectonic repetitions where simplified and even the great thrusts that he described were questioned. Only in the 70s, the detailed study of the main ridge in the San Juan sector made return to Schiller's ideas regarding structures and landslides in the Andes at these latitudes.
On January 20, 1835, a British merchant observed from the port of Valparaiso an erupting volcano and assumed that it was the Aconcagua. Just at that time Charles Darwin was walking through the port, to whom he told the story. Darwin had observed an eruption of Osorno volcano from the boat when they were heading north to Valparaiso. On that basis, the scientist repeated on several occasions, circles and publications that Aconcagua was an active volcano. His fame and prestige avoided questioning the claim until much later.
German Walter Schiller can be considered the greatest architect of knowledge of the geology of Aconcagua and although his greatest contributions date back to the early twentieth century, his Tectonic revolutionary ideas would not be fully accepted until past half century. His masterful work published in 1912: "The High Cordillera of San Juan and Mendoza and part of the province of San Juan," was misinterpreted and his conclusions were rejected. His remarks were reinterpreted, tectonic repetitions where simplified and even the great thrusts that he described were questioned. Only in the 70s, the detailed study of the main ridge in the San Juan sector made return to Schiller's ideas regarding structures and landslides in the Andes at these latitudes.
El basamento de los Andes en la zona del Aconcagua presenta una historia
compleja de acreciones y colisiones entre diferentes terrenos. Los afloramientos
de depósitos y rocas comienzan con un basamento previo al Jurásico. En el
Mioceno, hace 20Ma, se emplaza un arco magmático que da origen al Complejo Volcánico Aconcagua, nombre con que se
conoce a las rocas volcánicas de este cerro. Los materiales eruptivos
de una serie de volcanes se depositan discordantes con las rocas de la cobertera
sedimentaria jurásica y cretácica previamente deformada. Posteriormente estos edificios volcánicos son erosionados hasta no quedar pista de ellos. Por último, hace unos 8Ma se produce el evento final de
la Cordillera Principal en estas latitudes, plegando y elevando las rocas
yacentes, y dando lugar al levan tamiento del cerro
Aconcagua hasta las alturas que conocemos hoy en día.
The basement of the Andes in the Aconcagua area has a complex history of collisions and accretions occurred between different terrains. Deposits and rocks outcrops begin with a pre-Jurassic basement. In the Miocene, 20Ma ago, a magmatic arc stablishes that gives rise to the Aconcagua Volcanic Complex, name by which are known the volcanic rocks of this mountain. Eruptive materials of a series of volcanoes are deposited in discordance with the previously deformed rocks of the Jurassic and Cretaceous sedimentary cover. Subsequently all these volcanic edifices are eroded so that no track of them remains today. Finally, approximately 8MA ago, the final event of the Principal Cordillera in those latitudes occurs, folding and raising the rocks. During this movement it is that the Aconcagua is lifted to the heights we know today.
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