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Geología, S. Rosas

The plumbing system of a Volcano. Magma, which originates in the

partially molten asthenosphere, rises through the lithosphere to erupt on the surfaceas lava (from Press & Siever 2000). Geología, S. Rosas

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Geología, S. Rosas

Geología, S. Rosas(de Breitkreuz 2006)

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Geología, S. Rosas

Geología, S. Rosas

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Geología, S. RosasPillow Lavas, Cyprus (Akaki Canyon)

Mt. St. Helens, USA

Geología, S. Rosas

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Geología, S. RosasErupción del Monte Spurr en 1981 (de Viramonte 2006)

Geología, S. RosasErupción del Monte Redoubt (Alaska) en 1985 (de Viramonte 2006)

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Geología, S. Rosas(de Viramonte 2006)

Geología, S. Rosas

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Geología, S. Rosas

Volcán Pucón(Chile)

Stages in the evolution of a caldera. (a) Fresh magma fills a magma chamber and

triggers a volcanic eruption of lava and columns of incandescent ash. (b) Eruption of lava and pyroclastic flows continue, and the magma chamber becomes partly depleted. (c) A caldera results from the collapse of the mountain summit into the empty chamber. Largepyroclastic flows ejected from fractures accompany the collapse, blanketing the caldera andthe surrounding area. (d) A lake can form in the caldera. As the residual magma in thechambers cools, minor eruptive activity continues, with hot springs and gas emissions, anda small volcanic cone forms in the caldera (from Press & Siever 2000).

(a) (b)

(c) (d)

Geología, S. Rosas

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Geología, S. Rosas

A shield volcano is built up by the accumulation of thousands of thin basaltic

lava flows that spread widely and cool as gently sloping sheets. Each layer in this diagram represents an accumulation of many hundreds of thin lava flows. Magma can find alternate routes to the surface and erupt on the flanks of a volcano (from Press &Siever 2000).

Geología, S. Rosas

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Volcanic domes are bulbous masses of felsic lava, which are so viscous that,

instead of flowing, they pile up over the vent. Shown here is a growing dome within the crater of Mount St. Helens after the eruption (from Press & Siever 2000).

Geología, S. Rosas

In a cinder cone, ejected material is deposited as layers that dip away from

the crater at the summit. The vent beneath the crater is filled with fragmental debris(from Press & Siever 2000).

Geología, S. Rosas

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Geología, S. Rosas

A composite volcano is built up of alternating layers of pyroclastic material

and lava flows. Lava that has solidified in fissures forms riblike dikes that strengthen the cone (from Press & Siever 2000).

In a fissure eruption of highly fluid basalt, lava rapidly flows away from

fissures and forms widespread layers, rather than building up into volcanic mountain(from Press & Siever 2000).

Geología, S. Rosas

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Geología, S. RosasLahar de Armero, Colombia, en 1985 (de Alvarado 2006)

Geología, S. Rosas

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The active volcanoes of the world are not distributed randomly on

Earth’s surface. About 80 percent occur at boundaries where plates collide, 15 percent where plates separate, and the remaining few at intraplate hot spots. Convergent boundaries are shown in blue, divergent boundaries in orange. Black lines are transform faults. Active volcanoes are marked by red dots (from Press &Siever 2000). Geología, S. Rosas

A cross section of the East Pacific Rise in the South Pacific extending 400 kilometers from the ridge axis into Pacific Plate on the west and into the Nazca Plate on the east. Zone of partial melting is shown in orange. The asymmetry, with more melt coming from the Pacific Plate, has yet to be explained. Black arrows show convective flow and upwelling in the mantle that drive plates apart and direct the percolation of magmas into the gap between the separating plates (from Press & Siever 2000).

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