Igneous Structures and Field Relations-CH4

Central pumice cone 6600 bp is in left center big

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: w looking south. South rim of caldera is marked by steep cliff above the flow. • Big Obsidian flow (~1,400 BP) is in the foreground [images: Cascades Volcano Observatory - www.vulcan.wr.usgs.gov/Volcanoes/Newberry/Hazards/framework.html] 28 Pyroclastic deposits formed by accumulation of fragments of volcanic rock (pyroclasts) scattered by volcanic ejection into air: when P is release volatiles escape with explosive force, ejecting and farcturing magma formed from gas rich silicas Ash Eruption, Etna Volcano (2002), Italy Image source: www.photovolcanica.com 29 Pyroclastic deposits types of deposits classified according to size of fragments a) ash - <2mm, rock, mineral, glass fragments b) volcanic bombs Ash Eruption, Etna Volcano (2002), Italy Image source: www.photovolcanica.com 30 image source:Hamblin and Christiansen (2001) 10 8/27/2012 Pyroclastic deposits c) volcanic breccias - mixture of large and small angular material d) pyroclastic flows - also nuee ardente or glowing avalanche Mt Pelee, pyroclastic flow Types of pyroclastic flow deposits image source: Winter (2010) 31 Pyroclastic deposits (d) Pyroclastic flows – example - Mt. Pelee (1902) d) pyroclastic flows - Photograph of remains of St. Pierre (Martinique), 1902 Images: Volcano World site: http://volcano.und.nodak.edu/vwdocs/volc_images/img_mt_pelee.html]] 32 Pyroclastic deposits (d) Pyroclastic flows – example - Mt. Pelee (1902) Photograph of remains of St. Pierre (Martinique), 1902 33 11 8/27/2012 Pyroclastic deposits (d) Pyroclastic flows – Extent/character of pyroclastic deposits Areal extent of ash fall of 6950 YBP eruption of Crater Lake (Mt Mazama) d) pyroclastic flows - extent/ Areal extent of Bishop ash fall 700,000 YBP from Long Valley eruption image source: Winter (2010) 34 Pyroclastic deposits c) lahars - mud flows of wet volcanic material typically pyroclastic Broad summit of Nevado del Ruiz. Explosive eruption from Ruiz's summit crater on November 13, 1985, at 9:08 p.m. generated an eruption column and sent a series of pyroclastic flows and...
View Full Document

This document was uploaded on 07/18/2013.

Ask a homework question - tutors are online