felsic because its light coloured pumis rock froth

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: alls Clouds of pumice, fine-grained ash and acidic gases are propelled vertically, high into atmosphere. - felsic because it's LIGHT coloured - pumis = rock froth (soap = lava) Larger particles fall close to volcano, while finer particles settle farther away. - ash = respiratory probs, basically tiny pieces of glass - ash into plane engines, melt and gum up jets Consequences of ash Falls: Destruction of vegetation Surface water acidity Health = respiratory problems Aviation problems _________ Structural damage to buildings: settling on roof causes loading and subsequent collapse Primary Volcanic Hazards: Pyroclastic Flows Nuee ardente = “glowing cloud” of hot volcanic ash, boulders and gas - sucks up oxygen - hot enough, particles melted together (ash) Temperatures 100-600oC Travel >100 km/hr down slope. Obstructions knocked down or blown away suffocation is a major hazard _________ Ash can weld together in the heat = welded tuff 9 Historical Example of Volcanic Hazard: Eruption of Vesuvius Effects of ash fall and pyroclastic flow Vesuvius A.D. 79 - mount Vesuvius: intermediate to felsic magma - left with hollows (encaged in the ash) 4 cubic km of ash erupted in 19 hrs Nearby city of Pompeii buried under 3 metres of ash Rate of ash fall 12-15 cm/hr Followed by a Nuee Ardente City of Herculaneum buried under 23 metre-thick pyroclastic flow Killed 2000 people in a matter of minutes (plaster casts depicted people in last few seconds of life) - plaster casts of the ppl who died - the shock produces sumani Pliny the Younger reported earthquakes before eruption, details of the eruption itself and a tsunami generated by the explosion. Primary Volcanic Hazards: Poisonous Gas Lake Nyos, Cameroon A Killer Lake - carbon dioxide gass build up at bottom of lake - high winds, disturbance, gas escaped, flowed down side of volcano In 1986, carbon dioxide was suddenly released from the bottom of the lake (a volcanic crater) - turned orange from oxidized iron - was invisible even though not active Denser than air, the ___ carbon dioxide flowed downslope, killing more than 1700 people and livestock up to 25 km away More dangerous than carbon dioxide (which merely suffocates) are hydrogen sulphide (which legitima...
View Full Document

This document was uploaded on 02/25/2014.

Ask a homework question - tutors are online