Igneous Structures and Field Relations-CH4

M generated an eruption column and sent a series of

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: surges across volcano's broad icecovered summit. formed when flow meets heavy rain, ice melt, rivers extremely dangerous Río Lagunillas, former location of Armero. Within 4 hours of beginning of eruption, lahars had traveled 100 km: more than 23,000 people killed, about 5,000 injured, and more than 5,000 homes destroyed . Images: USGS volcanoes hazards site: http://volcanoes.usgs.gov/Hazards/What/Lahars/RuizLahars.html 35 Pyroclastic deposits – types of lithified rocks i. volcanic tuff - rock composed of pyroclastic fragments and ash a. welded tuff - fragments melt together on deposition Image source: Hamblin and Christiansen (2001) b. ash flow tuff - tuffs from ash flowing across surface c. air fall tuff - tuff from ash settling from atmosphere Piton del Teide (Canary Islands) - thick pumice layers (white in this image) interbedded with more locally-derived dark basaltic ash. image -Volcano World site: http://volcano.und.nodak.edu/vwdocs/volc_images/africa/piton_teide2.html] 36 12 8/27/2012 Pyroclastic deposits – types of lithified rocks ii. Volcanic Breccia Volcanic breccia (view is 0.3 m) [image source: Press and Siever, 2001] Volcanic breccia. Notice angular rock fragments consisting of flow-banded rhyolite. image source: http://www.maine.gov/doc/nrimc/mgs/explore/bedrock/site s/mar98-2.htm 37 Intrusive (plutonic) processes and bodies difficult to observe crystallizing intrusive body but infer shape and size 1. Tabular intrusive bodies Sill - tab intrusive that are concordant (along bedding plane) image source: Winter (2010) 38 Intrusive (plutonic) processes and bodies Dike - tab intrusive discordant Sills Salsbury Crags, Teschenite Sill (Edinburgh) Dolerite sill from Ross Sea, Antarctica Image source: www.rosssea.info/geology.html Sill from Big Bend, Texas 39 13 8/27/2012 Intrusive (plutonic) processes and bodies dike - tabular intrusive that is discordant i.e. cut across bedding/layering of country rock Dike cutting shales in the lower Grand Canyon Radial dike around volcanic neck at Spanish Peaks, CO Types of dikes cutting stratal features: (a) simple dilation and injection of magma (b) no dilation, but replacing or stoping. image source: Winter (2010) 40 Intrusive (plutonic) processes and bodies Veins - de...
View Full Document

This document was uploaded on 07/18/2013.

Ask a homework question - tutors are online