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Topic: Pyroclastic flow

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	Pyroclastic flow - Wikipedia, the free encyclopedia
		Pyroclastic flows are a common and devastating result of some volcanic eruptions.
		Flows containing a high proportion of gas to rock are known as pyroclastic surges.
		A pyroclastic flow is a type of gravity current; in scientific literature they are sometimes abbreviated to PDC (pyroclastic density current).
	en.wikipedia.org /wiki/Pyroclastic_flow (637 words)

	Wikipedia: Pyroclastic flow
		Another name for a pyroclastic flow is a nuée ardente (French for "fiery cloud"), which was first used to describe the 1902 Martinique eruption.
		Hot pyroclastic surges may form ahead of flows, for example during the eruption of Mount Pelee in 1902 a surge overwhelmed the city of Saint-Pierre and killed nearly 30,000 people.
		A pyroclastic flow is a type of gravity current; in scientific literature they are sometimes abbreviated to PDC - pyroclastic density current.
	www.factbook.org /wikipedia/en/p/py/pyroclastic_flow.html (592 words)

	Pyroclastic rock - Wikipedia, the free encyclopedia
		Pyroclastic rocks (tuff) are pyroclastic deposits which have been lithified.
		Pyroclasts are then entrained in a buoyant eruption plume which can rise several kilometres into the air and cause aviation hazards.
		Pyroclastic density currents, which are referred to as 'flows' or 'surges' depending on particle concentration and the level turbulence, are sometimes called 'glowing avalanches'.
	en.wikipedia.org /wiki/Pyroclastic (262 words)

	Lamington - Eruption Feature
		Pyroclastic flow is the term used to describe a combination of volcanic gases and fine ash particles that move down slope on the volcano flanks rather than rising like smoke as the ash cloud usually does.
		Pyroclastic flows move at speeds of 80 to 240 km/hour (50 to 150 mi/hour), although nuées ardentes may travel at twice that speed.
		Other types of pyroclastic flows include those in which the vent is open and a part of the ascending ash cloud collapses and flows down the sides of the volcano.
	www.ngdc.noaa.gov /seg/hazard/stratoguide/lamfeat.html (368 words)

	[No title]
		Pyroclastic flow deposits composed of mixtures of non-vesicular to partially or wholly vesicular, fine- to coarse-grained juvenile lithic particles, are known as block-and-ash flow deposits.
		Pyroclastic surges can override the sides of a valley and their deposits may mantle topography similar to fallout tephra, but unlike fallout tephra they are traceable into thicker pyroclastic flow deposits in valleys.
		The collapse of vertical eruption columns to form pyroclastic flows was recognized at the 1929 eruption of Komagatake, Japan (Kozu, 1934) and postulated from sedimentological data at St. Vincent, B.W.I. by Hay (1959).
	volcanology.geol.ucsb.edu /deposits.htm (2545 words)

	MSH Pyroclastic flow [USGS]
		Pyroclastic flows commonly are produced either by the fallback and downslope movement of fragments from an eruption column or by the direct frothing over at the vent of magma undergoing rapid gas loss.
		Pyroclastic flows originated in both ways at Mount St. Helens on May 18, but flows of mappable volume were of the latter type.
		Pyroclastic flows were first directly observed shortly after noon, although they probably began to form a short time after the lateral blast.
	pubs.usgs.gov /gip/msh/pyroclastic.html (488 words)

	CVO Website - Pyroclastic Flows and Surges
		Pyroclastic flows are high-density mixtures of hot, dry rock fragments and hot gases that move away from their source vents at high speeds.
		Pyroclastic flows may also result from a laterally directed explosion, or the fall of hot rock debris from a dome or thick lava flow.
		Pumiceous pyroclastic flows with volumes of 1-10 cubic kilometers can reach distances of several tens of kilometers from a vent and travel downslope at speeds of 50 to more than 150 kilometers per hour, their velocity depending largely on their volume and on the steepness of slopes over which they travel.
	vulcan.wr.usgs.gov /Glossary/PyroFlows/description_pyro_flows.html (1503 words)

	Volcanic Hazards: pyroclastic flows and surges
		Pyroclastic flows are high-density mixtures of hot, dry rock fragments and hot gases that move away from the vent that erupted them at high speeds.
		Pyroclastic flows generally follow valleys or other low-lying areas and, depending on the volume of rock debris carried by the flow, they can deposit layers of loose rock fragments to depths ranging from less than one meter to more than 200 m.
		Hot pyroclastic flows and surges can also directly generate lahars by eroding and mixing with snow and ice on a volcano's flanks, thereby sending a sudden torrent of water surging down adjacent valleys (see case study from Nevado del Ruiz volcano, Colombia).
	volcanoes.usgs.gov /Hazards/What/PF/pcflows.html (429 words)

	[No title]
		Pyroclastic flows are heavier-than-air gas-particle emulsions that travel across the ground at velocities ranging from 10 m/sec to 300 m/sec.
		The term "pyroclastic surge" is a synonym for "dilute pyroclastic flow." As shown by lateral facies transitions in pyroclastic flow deposits, pyroclastic flows and surges commonly develop simultaneously from the same flow and evolve one from the other.
		The collapse of vertical eruption columns to form pyroclastic flows was recognized at the 1929 eruption of Komagatake, Japan (Kozu,1934) and postulated from sedimentological data at St. Vincent, B.W.I. by Hay (1959).
	volcanology.geol.ucsb.edu /pfs.htm (1108 words)

	Vic Camp - Pyroclastic flows
		The extraordinary velocity of a pyroclastic flow is partly attributed to its fluidization.
		The expanding gas component is derived from a combination of (1) the constant exsolution of volcanic gas emitted by the hot pyroclasts, and (2) from the ingestion, heating, and rapid expansion air during movement of the flow.
		Pumice flows are pumice-rich pyroclastic flows derived from the collapse of an eruption column.
	www.geology.sdsu.edu /how_volcanoes_work/Pyroflows.html (1105 words)

	USGS Photo Glossary:
		A pyroclastic flow is a ground-hugging avalanche of hot ash, pumice, rock fragments, and volcanic gas that rushes down the side of a volcano as fast as 100 km/hour or more.
		Pyroclastic flow sweeps down the side of Mayon Volcano, Philippines, during an explosive eruption on 15 September 1984.
		Note the ground-hugging cloud of ash (lower left) that is billowing from the pyroclastic flow and the eruption column rising from the top of the volcano.
	volcanoes.usgs.gov /Products/Pglossary/PyroFlow.html (148 words)

	Pyroclastic Flow (Site not responding. Last check: 2007-11-07)
		Pyroclastic flow is composed mainly of volcanic rock and dense ash material and is ejected from an exploding volcano.
		Also, it is thought that past pyroclastic flows have mixed with snow, ice and other debris and changed into lahars.
		The pyroclastic flow could turn into a lahar, and lahars are a greater threat.
	www.uccs.edu /~geogenvs/ges199/rainier/pyroclas.htm (176 words)

	Pyroclastic Flow - John Seach (Site not responding. Last check: 2007-11-07)
		Pyroclastic Flows and Nuée ardentes are the most dangerous of all the volcanic eruption styles.
		Pyroclastic flows are clouds of hot gas, ash, and clasts which move down hill under the action of gravity.
		Pyroclastic flows are driven by gravity and are channeled into valleys.
	www.volcanolive.com /pyroclastic.html (102 words)

	The Structural Effects of Pyroclastic Flow
		The effects of the pyroclastic flow were thoroughly investigated and documented by G.A Taylor [1958], and his observations provide valuable insights into the behavior of pyroclastic phenomena.
		Taylor identified an inner zone of total destruction, where the kinetic force and temperature of the nueée destroyed nearly everything in the region, surrounded by a region of partial destruction, where the velocity of the nueée had reduced and the damage was primarily due to temperature [1958, p.
		Like the pyroclastic surges of the 1902 eruption of Mt. Pelée, the zone of devastation extended approximately 10-12 km from the crater, and was strongly influenced by topography, which directed flows more strongly toward the west and south at Pelée, and toward the northeast at Lamington, due to the geometry of the crater.
	urban.arch.virginia.edu /struct/pompeii/pyroclastic-5.html (1120 words)

	Mount St. Helens Erupts a Pyroclastic Flow
		The vertical eruption column of ash and pumice rises directly from the crater, whereas the ash cloud rising through the white clouds in the background rises from a pyroclastic flow that is rushing down the north flank of the volcano.
		The pyroclastic flow was generated by the collapse of a "fountain" of erupting magma.
		Viewed from the southeast, the pyroclastic flow is clearly separate from the darker vertical eruption column.
	www.solarviews.com /cap/volc/helens1.htm (191 words)

	Pyroclastic Flows (Site not responding. Last check: 2007-11-07)
		Pyroclastic flows are fluidized masses of rock fragments and gases that move rapidly in response to gravity.
		The flow is fluidized because it contains water and gas from the eruption, water vapor from melted snow and ice, and air from the flow overriding air as it moves downslope (Scott, 1989).
		Pyroclastic flows and lahars are the greatest volcanic hazards.
	www.geo.mtu.edu /volcanoes/hazards/primer/pyro.html (664 words)

	W.E. Scott
		We infer that pyroclastic flows were generated by either quasicontinuous, low-level collapse of portions of a sustained plinian column or by repeated brief collapse of the entire column.
		Pyroclastic flow, as used in this report, is a general term for hot, gravity-driven density currents of gas and particles that range from dense flows, whose flow regime is thought to be dominantly laminar, to turbulent flows having a lower particle concentration.
		Pyroclastic flows crossed the 200- to 400-m-high ridge 3 km northeast of the former summit of Pinatubo and flowed down the east tributaries of the O'Donnell River (Bangat and several unnamed streams between the Bangat and main O'Donnell) and the Malago River (western tributary of the Marimla River).
	pubs.usgs.gov /pinatubo/wescott (11778 words)

	Mount St. Helens, During the Eruption, Pyroclastic Flow (Site not responding. Last check: 2007-11-07)
		North of the volcano, these flows deposited pumice and ash in layers as thick as 60 feet.
		Pyroclastic flow deposits are easily eroded by wind and water because they are made of loose ash and pumice.
		North of the volcano and directly in front of the crater is a fan-shaped deposit area known as the Pumice Plain, because it is covered with pyroclastic flow deposits.
	volcano.und.nodak.edu /vwdocs/msh/ov/ovd/ovdpf.html (148 words)

	Pyroclastic flow evident at WTC? (Site not responding. Last check: 2007-11-07)
		In the raw footage, there is clear evidence of these ‘clouds flowing down the street’ and into the harbor in an almost identical fashion as those pyroclastic flows observed during volcanic activity.
		Pyroclastic flows are a very specific and not widely understood physical phenomenon that played an prominent role in the in the physical appearance of the WTC collapses.
		Pyroclastic flows can only occur when a dense slurry of fine dust is suspended in air or volcanic gasses and is concentrated in a defined area.
	www.gnn.tv /threads/11223/Pyroclastic_flow_evident_at_WTC (3705 words)

	pyroclastic flow - Article and Reference from OnPedia.com
		pyroclastic flow - Article and Reference from OnPedia.com
		Flows usually consist of two parts - the basal flow hugs the ground and contains larger, coarse boulders and rock fragments, while an ash cloud rises above it because of the turbulence between the flow and the overlying air.
		Collapse of a volcanic dome and its subsequent flow down a steep slope (e.g.
	www.onpedia.com /encyclopedia/pyroclastic-flow (590 words)

	The Structural Effects of Pyroclastic Flow
		The figure below shows a map of the region surrounding Mt. Pelée, where a heavy line marks the "zone of devastation" for the 8 May eruption (the May 20 eruption did not surpass this boundary) and a dotted line marking the increase in the zone resulting from the eruption of 30 August.
		The isopach map reveals that the dense deposits of pyroclastic flow are limited to the valley surrounding a river that ran south-west from the crater, while the ash deposits of pyroclastic flow are much more widespread because of the greater motility of the less-dense surge clouds.
		Although the city of St. Pierre was near the fringe of the surge area affected by the 8 May and 20 May eruptions, with deposits ranging from 1 m (3.3 ft) to zero, it was nonetheless completely destroyed.
	urban.arch.virginia.edu /struct/pompeii/pyroclastic-2.html (532 words)

	Pyroclastic flow (Site not responding. Last check: 2007-11-07)
		Pyroclastic flows are produced when large portions of the dome collapse and disintegrate.
		Eruption columns from explosive magmatic eruptions may collapse to form pyroclastic flows.
		The jet of ash and gas erupting from the vent heats cold air in the atmosphere.
	www.bgs.ac.uk /education/montserrat/Pyroclasticflow.htm (230 words)

	4. Modelling erosion from pyroclastic flow deposits on Mount Pinatubo
		The rapid erosion or removal of the 1991 pyroclastic flow deposit is one of the major social and scientific concerns after the 1991 eruption of the Pinatubo Volcano as life threatening and destructive lahars of enormous magnitude are generated.
		To calculate the volume of the 1991 pyroclastic flow deposits and the yearly eroded sediment volumes, a DTM overlaying technique using GIS was applied.
		First the changes in the catchment sizes are calculated that are the result of the accumulation of the pyroclastic flow deposits.
	www.itc.nl /ilwis/applications/application04.asp (1033 words)

	MAJOR PYROCLASTIC FLOW DEPOSITS (Site not responding. Last check: 2007-11-07)
		The area SSW of Tacaná's summit, extending down to Córdova and Unión Júarez (Mexico) is interperted in the aerial photographs as a large-scale pumiceous pyroclastic flow.
		These flows will tend to be channelized to existing drainages, but they could break across the topographic barriers.
		Pumiceous pyroclastic flows are common from many Central American and Caribbean volcanoes, but have occurred much in historic eruptions.
	www.geo.mtu.edu /volcanoes/tacana/pyroflow.html (128 words)

	Pyroclastic Flow Map (Site not responding. Last check: 2007-11-07)
		This is a composite of the southern section of the tourist map and a much processed copy of a map of the extent of the pryroclastic flows that I saw hanging on the wall at the MVO.
		The overlay showing the extent of the pyroclastic flows is derived from one of several photos I took of a hand drawn map that I found hanging on the wall of the Montserrat Volcano Observatory.
		Once this was accomplished I overlaid the flow diagram onto the tourist map.
	mni.ms /pflowmap/index.shtml (262 words)

	Earth Science Picture of the Day (Site not responding. Last check: 2007-11-07)
		This pyroclastic flow deposit is located in Poseidon's Gardens, near Citara on the island of Ischia, Italy.
		This deposit indicates the violent nature of pyroclastic flows, and the turbulence and deformation possible within these volcanic features.
		These soft volcanic layers were deposited about 10,000 years ago, and deformed as the flow slid down the side of the mountain, or possibly as the soft sediments were covered by a more viscous lava flow during the same eruption.
	epod.usra.edu /archive/epodviewer.php3?oid=131680 (171 words)

	CVO Menu - Pyroclastic Flows and Surges
		Hazards: Pyroclastic Flows -- Excerpt from: Hoblitt, et.al., 1987, USGS Open File Report 87-297
		Pyroclastic Flows - Mount St. Helens, May 18, 1980 -- Excerpt from: Tilling, et.al., 1990
		Volcano Hazards Factsheet: Hazardous Phenomena at Volcanoes -- section on Pyroclastic Flows and Pyroclastic Surges -- Myers and Brantley, 1995, USGS Open-File Report 95-231
	vulcan.wr.usgs.gov /Glossary/PyroFlows/framework.html (258 words)

	Phonolitic pyroclastic flow, Pitigliano, Grosseto Province, Tuscany, Italy
		Phonolitic pyroclastic flow, Pitigliano, Grosseto Province, Tuscany, Italy
		Pegmatoid syenite ejectum in a phonolitic pyroclastic flow.
		The above list contains all mineral locality references listed on mindat.org.
	www.mindat.org /loc-68280.html (93 words)

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