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Topic: Pyroclastic rock

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	Pyroclastic flow - Wikipedia, the free encyclopedia
		Hot pyroclastic surges may form ahead of flows, for example during the eruption of Mount Pelée 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).
		Frothing at the mouth of the vent during degassing of the erupted lava at the mouth.
	en.wikipedia.org /wiki/Pyroclastic_flow (636 words)

	Amateur Geologist Structured Geological Glossary: Igneous Rocks
		Rocks are made of different kinds of mineral, or broken pieces of crystal, or broken pieces of rocks.
		The unsorted, angular, and un-rounded texture of the fragments in a pyroclastic rock.
		Sedimentary rock undergoes metamorphism at greater depths or is uplifted and exposed to erosion.
	www.amateurgeologist.com /content/glossary/rock/igneous.html (4089 words)

	Wikipedia: Pyroclastic flow
		Flows usually consist of two parts - the basal flow hugs the ground and contains larger, coarse boulders and rock fragments, whilst an ash cloud rises above it because of the turbulence between the flow and the overlying air.
		Another name for a pyroclastic flow is a nuée ardente (French for "fiery cloud"), which was first used to describe the 1902 Martinique eruption.
		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)

	Vic Camp - Tephra and Pyroclastic Rocks
		Pea- to walnut-size pyroclasts (2 to 64 mm).
		Pyroclastic airfall deposits (tephra) contain pyroclasts that are coarser near the vent (bomb and lapilli size) and become increasingly finer grained away from the vent (lapilli to ash size).
		Dark pyroclasts of basaltic scoria are typical of Strombolian airfall accumulations, whereas light colored pyroclasts of felsic pumice and ash are typical of Plinian airfall accumulations.
	www.geology.sdsu.edu /how_volcanoes_work/Tephra.html (610 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)

	Amateur Geologist Geological Glossary - V
		Elements that are soluble in magma at elevated pressure and temperature that exsolve as gas from magmas during ascent and eruption at the earth's surface.
		Arc rocks are mostly volcanic rock from the volcanoes and sedimentary rocks made up of eroded debris from the volcanoes.
		Melted rock in the deeper plumbing of the arc which may crystallizes at depth to become an arc root pluton.
	www.amateurgeologist.com /content/glossary/glossary_v.html (868 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.
		With rock fragments ranging in size from ash to boulders traveling across the ground at speeds typically greater than 80 km per hour, pyroclastic flows knock down, shatter, bury or carry away nearly all objects and structures in their way.
		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.
	volcanoes.usgs.gov /Hazards/What/PF/pcflows.html (429 words)

	Vocab3Teacher
		Angular pieces of pyroclastic rock that is exploded from a volcano during an eruption.
		Pyroclastic rock that is in a semi-plastic state as it is shot through the air.
		This rock moves from the lower reaches of the mantle to the surface of the Earth causing the formation of volcanoes.
	volcano.und.nodak.edu /vwdocs/vwlessons/lessons/Ch3CM/Vocab3Teacher.html (1032 words)

	Eastern Mojave Vegetation - A
		The rock is chiefly a fine grained rhyolitic tuff formed mainly of glass particles (shards) in which crystals of feldspar, quartz, and occasionally hypersthene or hornblende are embedded.
		Pyroclastic ejecta, usually of basic composition, characterized by marked vesicularity, dark color, heaviness, and a texture that is partly glassy and partly crystalline.
		The loose fragments of minerals and rocks which are transported by the wind, rivers, and glaciers as well as currents in lakes and the ocean.
	ucjeps.berkeley.edu /Alexander/glossaryA.html (2824 words)

	Pyroclastic Flows (Site not responding. Last check: 2007-10-09)
		Therefore, pyroclastic is a term used for broken pieces of rock associated with volcanic eruptions.
		Pyroclastic flows are also referred to as pyroclastic clouds, and as "nuee ardentes" - a French term which means "glowing cloud." They are hot and fast, moving at speeds up to several hundred miles per hour and at temperatures of several hundred degrees Celsius.
		Pyroclastics are common to intermediate volcanoes such as are associated with subduction of the crust.
	jersey.uoregon.edu /~mstrick/AskGeoMan/geoQuerry33.html (268 words)

	Glossary V (Site not responding. Last check: 2007-10-09)
		: A rock that exhibits the effects of sandblasting or "snowblasting" on its surfaces, which become flat with sharp edges in between.
		: A volcanic sediment of rock fragments, usually glass, less than 2 mm in diameter, that is formed when escaping gases force out a fine spray of magma.
		: A consolidated rock composed of pyroclastic rock fragments and fine volcanic ash welded together by their own heat.
	www.whfreeman.com /presssiever/content/glossary/glossaryV.html (252 words)

	CVO Website - Pyroclastic Flows and Surges
		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 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.
	vulcan.wr.usgs.gov /Glossary/PyroFlows/description_pyro_flows.html (1503 words)

	Mineral Resources Data System
		Volcanic Rock (Aphanitic) > Pyroclastic Rock > Tuff > Ash-Flow Tuff
		Volcanic Rock (Aphanitic) > Mafic Volcanic Rock > Basalt > Tholeiite
		A schistose metamorphic rock derived by metamorphism of an argillaceous or a fine-grained alluminous sediment.
	tin.er.usgs.gov /metadata/mrds.faq.html (6865 words)

	Groundwater Res. of Sonoma Co. v.1
		Rock formed from the solidification of molten magma, either at depth or on the ground surface.
		In sedimentary rock, primary openings are usually the result of the arrangement and nature of the original sediment.
		As applied to a rock or soil unit, it is the ratio of (1) the volume of water which, after being saturated, it will yield by gravity to (2) its own volume.
	www.sonoma.edu /users/n/norwick/document/Ford/gwsappb.html (2660 words)

	Petrology (Site not responding. Last check: 2007-10-09)
		Pyroclastic rocks are formed of fragmented material ejected into the atmosphere by disruptive volcanic eruption.
		Pyroclastic flow is a rapidly moving mass of lava buoyed up by gases released near the vent.
		Agglomerate is a rock formed by the consolidation of angular fragments (blocks) in an ash matrix, and formed from explosive volcanic activity.
	www.burdon.demon.co.uk /g7-2.htm (1447 words)

	Introduction & Textures & Structures of Igneous Rocks
		A magma consists mostly of liquid rock matter, but may contain crystals of various minerals, and may contain a gas phase that may be dissolved in the liquid or may be present as a separate gas phase.
		Intrusions that intrude rocks at shallow levels of the crust are termed hypabyssal intrusions.
		Very little pyroclastic material is found within a shield volcano, except near the eruptive vents, where small amounts of pyroclastic material accumulate as a result of fire fountaining events.
	www.ntnu.no /~krill/mineralogee/petrologee/1.htm (3896 words)

	MASSIVE COLLAPSE OF CERRO QUEMADO 1200 YEARS AGO
		The sequence of events during this episode of volcanism was: shallow intrusion or extrusion and cooling of magma, disruption and failure of the edifice, laterally-directed explosions due to disruption and fragmentation of hot dome rock, pyroclastic flows derived from secondary flow of hot lateral blast deposits down steep slopes, and subsequent rain-induced lahars.
		These vesicular juvenile rocks and charred stems indicate that the fines-poor pyroclastic flow was hot, and its wide distribution and the absence of fine ash suggests it was energetic and highly inflated.
		The pyroclastic flow deposit forms a discontinuous sheet, extending from the south end of the valley to the lower north-central end, and is thickest where it abuts Siete Orejas.
	www.geo.mtu.edu /volcanoes/quemado/collapse4.html (1365 words)

	Open University S260 Thin Rock Sections. Selected Image Gallery.
		General: Dolerite is an igneous rock and is one of the varieties of basalt and coarse grained in texture.
		General: Amphibolite is a metamorphic rock and varies in grain size from coarse to fine, comprising mostly hornblende and plagioclase with smaller quantities of other minerals depending on location.
		General: Ignimbrite is an igneous rock [Latin: 'fire cloud'] these rocks start off as hot fragments thrown out of volcanoes, reaching the ground still in a molten state, they build up and fuse together to create a compact rock also known as pyroclastic rock.
	www.microscopy-uk.org.uk /mag/artfeb04/iwouslides2.html (627 words)

	Igneous Rocks (Site not responding. Last check: 2007-10-09)
		List the different igneous rock textures (aphanitic, phaneritic, porphyritic, pegmatitic, vesicular, glass, and pyroclastic) and explain their origins.
		Igneous rocks are classified on their texture and their composition.
		May also resemble a sedimentary conglomerate or breccia, except that rock fragments are all fine-grained igneous or vesicular.
	www.gpc.edu /~pgore/geology/geo101/igneous.htm (614 words)

	Geology 1 with Terry J. Boroughs: Volcanism and Weathering for Fri/Sat Section
		A rock composed primarily of hydrous aluminum oxides, formed by intense chemical weathering.
		A physical weathering process in which sheets of rock are fractured and detached from an outcrop.
		Large and relatively planar fractures in a rock across which there is no relative displacement of the two sides.
	www.arc.losrios.edu /~borougt/FSVolcanismWeatheringHomework.htm (1687 words)

	Mineral Resources Data System
		Volcanic Rock (Aphanitic) > Glassy Rock > Pumice A light-colored vesicular glassy rock commonly having the composition of rhyolite.
		Volcanic Rock (Aphanitic) > Mafic Volcanic Rock > Basalt > Alkaline Basalt A basalt with nepheline and/or acmite in the CIPW norm.
		Metamorphic Rock > Schist > Pelitic Schist A schistose metamorphic rock derived by metamorphism of an argillaceous or a fine-grained alluminous sediment.
	tin.er.usgs.gov /metadata/mrds.xml (6838 words)

	GLY 220 Physical Geology Notes
		Form by: Eruptions of (1) intermediate lava flows, which commonly perch near the volcano crater, and (2) pyroclasts (and pyroclastic flows) from explosive, ash-rich eruptions.
		Internals: piles of coarse pyroclasts, usually scoria, with larger bombs near the crater and smaller ones down the flanks.
		Pyroclastic — Rock made of pyroclasts: Tuff (ash) and breccia (coarser grained pyroclasts) are the common pyroclastic rocks.
	www.uky.edu /AS/Geology/howell/220/unit3b.html (1133 words)

	Volcanic ash and tuff
		Volcanic ash is a pyroclastic rock, composed of fine grains less than 2mm in diameter.
		Pyroclastic means ‘fire-broken’, a name for rocks that have been blown apart by exploding gases.
		Composition: ash-fall tuffs composed of a mixture of rock fragments, crystals and glass shards.
	www.es.ucl.ac.uk /schools/Glossary/tuff.htm (122 words)

	Volcano Terminology Pt. 4
		Pyroclastic Flow: A turbulent flow of pyroclastic material and hot gases.
		Scoria: Vesicular glassy lava rock composed of basalt and andesite which is expelled from a vent during an explosive eruption.
		Vesicle: A small air pocket, or cavity in volcanic rock, resulting from a the entrapment of a gas bubble during solidification.
	www.paricutin.com /volcano_terminology_004.htm (301 words)

	Igneous and Metamorphic Rocks
		The heated water reacts locally with the hot rock and carries a load of dissolved matter (rich in metals and sulfer) from the region of high heat into a region of cooler rock (or water).
		Also, parent rocks (protoliths) that tend to grow minerals that are not platey or elongated, will produce metamorphic rocks that have no foliation or lineation.
		Rocks melt when the temperatures, pressures, and/or water content are sufficient to bring the rock to the melting tempertare (duh).
	topex.ucsd.edu /es10/lectures/lecture16/lecture16.html (1809 words)

	[No title]
		Tuff is a pyroclastic (ejected) rock composed of ash-sized fragments.
		Pyroclastic flows are fluid and fast-moving because of their dissolved gas content.
		Tuff is a pyroclastic rock, and there is virtually no pyroclastic activity associated with spreading center vulcanism.
	www.usd.edu /exam/esci/igneous.txt (2427 words)

	Igneous Rocks
		The study of igneous rocks is important because as products of deep Earth processes such as melting of solid rock and crystallization of molten rock (magma), they provide us with important information regarding the mineralogical and chemical composition of the Earth's interior.
		So, through the study of igneous rocks we learn much about processes which occur within volcanoes, and the forces which power volcanic eruptions.
		Rock Cycle - The sequence of events in which rocks are formed, destroyed, altered and reformed by geologic processes.
	mtsu32.mtsu.edu:11407 /100igneous.html (888 words)

	Tephra - TheBestLinks.com - Greek language, Volcanic ash, Pyroclastic rock, Lapilli, ... (Site not responding. Last check: 2007-10-09)
		Once they have fallen to the ground they are still called tephra unless they are hot enough to fuse together into pyroclastic rock.
		The distribution of tephra following an eruption is usually such that the largest boulders fall to the ground quickest and therefore closest to the vent, whilst smaller fragments travel further - ash can often travel for thousands of miles as it can stay in the stratosphere for several weeks.
		Both tephra and pyroclast are derived from Greek.
	www.thebestlinks.com /Tephra.html (199 words)

	Chapter 6
		are rocks that solidified from a magma or lava
		is a mafic volcanic rock consisting primarily of plagioclase feldspar, pyroxene, and olivine
		xenolith is a fragment of rock that is enclosed in the solidified magma
	www2.hawaii.edu /~younggeo/GG101/Ch6.htm (1389 words)

	Volcanic Rocks: Review Sheet
		Enter relative crystal size (coarse, fine), cooling rate (slow, fast), and indicate whether the rock type is intrusive or extrusive
		Enter the names for extrusive and intrusive rock types corresponding to each of the three mineral assemblages
		Enter the names for each of the pyroclastic rock types.
	www.indiana.edu /~volcano/notes/VolcanicRocks.htm (50 words)

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