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Topic: Volcanic plug

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	USGS Photo Glossary: Lava dome
		Volcanic domes are rounded, steep-sided mounds built by very viscous magma, usually either dacite or rhyolite.
		Volcanic domes are also referred to as lava domes.
		The volcanic dome in the Cascades is Lassen Peak in northern California.
	volcanoes.usgs.gov /Products/Pglossary/LavaDome.html (393 words)

	The Dirty Rag - The International Volcanic Abatement Treaty - Sheldon Wimpfen
		Plugs of a size easily transported by the largest helicopters would be manufactured in large quantities.
		As plug size would be limited by the lifting capacity of the helicopters and balloons involved, they are not expected to have dimensions greater that 20x20x20 feet.
		Subsequently an International Volcanic Abatement Treaty (IVAT) should be forthcoming so that the entire world may act in concert towards the reduction and eventual elimination of volcanoes as a source of greenhouse gases and damaging particulates.
	www.thedirtyrag.com /articles/sw_volcano.php (1118 words)

	The Nature of Volcanoes
		As the cone is stripped away, the hardened magma filling the conduit (the volcanic plug) and fissures (the dikes) becomes exposed, and it too is slowly reduced by erosion.
		Enormous volumes of volcanic ash and dust were expelled and swept down the slopes as ash flows and avalanches.
		Volcanic or lava domes are formed by relatively small, bulbous masses of lava too viscous to flow any great distance; consequently, on extrusion, the lava piles over and around its vent.
	www.solarviews.com /eng/tervolc3.htm (1257 words)

	Volcanic and Geologic Terms
		Dacite: Volcanic rock (or lava) that characteristically is light in color and contains 62% to 69% silica and moderate a mounts of sodium and potassium.
		Hot Spot: A volcanic center, 60 to 120 miles (100 to 200 km) across and persistent for at least a few tens of million of years, that is thought to be the surface expression of a persistent rising plume of hot mantle material.
		Plug Dome: The steep-sided, rounded mound formed when viscous lava wells up into a crater and is too stiff to flow away.
	volcano.und.nodak.edu /vwdocs/glossary.html (4560 words)

	Volcanic Processes (Site not responding. Last check: 2007-10-22)
		Abundant volcanism (most of it actually) does of course occur along the mid-oceanic ridges, but because these are covered with water we don't have much opportunity to see it.
		Additional volcanic activity is found in zones of crustal extension (continental rifts) where faulting provides a conduit for magma to reach the surface.
		Volcanic debris is transported onto the surrounding area through direct eruption, wind and water, and landslides from the flanks of the volcano.
	www.indiana.edu /~geol105/images/gaia_chapter_5/volcanic_processes.htm (1074 words)

	Ukvolc
		Volcanism, is thought to have started to the west of Britain in the Late Jurassic and local sites in the North Sea Basin were active through the Late Jurassic into the Early Cretaceous.
		Volcanic ash would have been blown clear of the vent, but coarser lava or agglomerate, comprising pebbles, cobble or boulder sized blocks of rock would have remained within the confines of the crater, which may have been several kilometres in width.
		The volcanic pipe, which was the conduit through which the lava was erupted, forms the bulk of Arthur's Seat itself, and the lava flows which form the flanks of the volcano are exposed on the eastern side of the park (left hand side of the ilustration above, which is looking South).
	www.geologyshop.co.uk /ukvolc.htm (4372 words)

	ROCK LANDFORMS of Australia & NZ - IGNEOUS LANDFORMS - Case Study (A)
		Volcanic rocks are igneous rocks that have cooled at or near the Earth's surface from lava, ash, and/or other materials associated with volcanic activity.
		Crater Bluff is a 'classic' volcanic plug (or neck) of hard trachyte and its faces are used regularly for rock climbing.
		The resistant plug is prominent now as adjacent softer materials (tuff and breccias) have been removed by erosion, leaving the plug surrounded by a bowl-shaped depression.
	www.vnc.qld.edu.au /enviro/landform/landf-ic.htm (647 words)

	Stark's Knob - Geological Origins
		Volcanic rock is of two main types-1) Mount St. Helen's- or east Pacific-type andesites, which result from explosive eruptions of stiff, silica-rich lava (i.e., liquid rock), and 2) the Hawaiian Island- or Icelandic-type that feature flows of very hot basalt lava from deep in the earth.
		As the volcanic arc was pushed west into Vermont and eastern New York and the continent buckled in front of it, cracks opened in the earth's crust.
		It has been described at length in the reports of the Geological Survey as a volcano or volcanic plug and as such is the only geological phenomenon of this kind known to occur in the State of New York.
	www.nysm.nysed.gov /services/starks/starktwo.html (679 words)

	WEAVER'S NEEDLE OR PICACHO
		The rock in a volcanic plug is quite consistent after the cessation of an eruption.
		A classic example of a volcanic plug exposed to the elements is Shiprock located on the Navajo Indian Reservation in northwestern New Mexico.
		Weaver's Needle is composed of alternating layers of ash and basalt.
	www.ajpl.org /aj/superstition/1eedle.htm (743 words)

	Volcanic plug - Wikipedia, the free encyclopedia
		A volcanic plug, also called a volcanic neck or lava neck, is a volcanic landform created when lava hardens within a vent on an active volcano.
		If a plug is preserved, erosion may remove the surrounding rock while the erosion-resistant plug remains, producing a distinctive landform.
		The only example of a volcanic plug in the eastern USA is the highly eroded Stark's Knob basaltic structure located along the Hudson River near Saratoga Springs, New York.
	en.wikipedia.org /wiki/Volcanic_plug (235 words)

	Lassen Volcanic National Park, Lassen Park History
		Volcanic eruptions are linked to the slow grinding of the continent-sized plates drifting across the surface of our planet which float on top of a softer underlying mantle.
		The Dittmar Volcanic Center, the oldest of the three centers, is located in Warner Valley in the southeast corner of the park.
		Lassen Peak is a lava dome or plug dome volcano that formed on the flank of its ancestral Mt. Tehama.
	www.shastahome.com /lassen-volcanic/volcanic_history.htm (1020 words)

	Geo112 Volcanos lecture
		Volcanic topography is built by the extrusion onto the earth's surface of molten material called lava.
		More volcanic rock is extruded each year by fissure eruptions along seafloor spreading centers than by any other type of volcanism.
		Volcanic material from the landslide traveled 75 miles and buried parts of the countryside to depths of 650 feet.
	www.geology.wisc.edu /courses/g112/volcano.html (1977 words)

	Types of Volcanoes — FactMonster.com
		Finally, all that remains is the plug and dike complex projecting above the land surface—a telltale remnant of the vanished volcano.
		Volcanic domes commonly occur within the craters or on the flanks of large composite volcanoes.
		Volcanic Eruptions - Volcanic Eruptions A volcanic eruption occurs when molten rock, ash and steam pour through a vent...
	www.factmonster.com /ipka/A0862596.html (1345 words)

	Goemmer Butte vicinity (Site not responding. Last check: 2007-10-22)
		Goemmer Butte is considered by some to be a "volcanic plug" in which magma vented to the surface (Penn and Lindsey 1996).
		The evidence for this volcanic interpretation is the breccia pipe that partly surrounds the butte's core.
		Breccia is associated with explosive volcanic eruptions in which pre-existing rocks are broken, mixed, and violently ejected by high-pressure gas/steam explosions.
	academic.emporia.edu /aberjame/field/rocky_mt/goemmer.htm (574 words)

	[No title]
		The present outcrop belt of volcanics is the remnant of a once extensive sheet that was extruded on to a surface of moderate relief and with a northwest drainage direction (Gee, 1971).
		It is a flat topped, more or less circular volcanic plug of dolerite containing olivine, titanaugite, labradorite, sanidine, analcite, and rare nepheline.
		In Chambers Bay, immediately west of the volcanic neck, a layer 18m thick of scoriaceous and amygdaloidal lava underlies the main pile of lavas.
	www.chez.com /mineralzine/ancien/info5-1-b.htm (727 words)

	Lassen Volcanic National Park - Wikipedia, the free encyclopedia
		The source of heat for volcanism in the Lassen area was, and still is, subduction off the Northern California coast of the Gorda Plate diving below the North American Plate.
		Lassen Volcanic National Park is one of the few areas in the world where all four types of volcano can be found (plug dome, shield, cinder cone, and strato).
		It was made of roughly alternating layers of andesitic lavas and tephra (volcanic ash, breccia, and pumice) with increasing amounts of tephra with elevation.
	en.wikipedia.org /wiki/Lassen_Volcanic_National_Park (2164 words)

	Geoscience - The Earth - Australian Landforms - Mt. Warning
		Mt. Warning is Australia's most prominent volcanic plug.
		It is all that is left of the eroded core of the Tweed Shield Volcano, Australia's largest central volcano, which formed about 22 million years ago and straddles the New South Wales-Queensland border.
		The trachyandesite plug (with minor plugs and radiating dykes) which is the central part of Mt. Warning rises to 1156 m, penetrating the volcano's outer ring dykes of syenite, as well as the surrounding gabbro and monzonite intrusion (itself intruded by the syenite) that now forms the plug's outer slope.
	www.amonline.net.au /geoscience/earth/warning.htm (219 words)

	NPS Publications: The Geology of Devils Tower National Monument
		The occurrence of these trachytic peaks appears like a great postular outbreak on the surface of the northern end of the Black Hills, whereby the deep-seated igneous forces were relieved, or like the appearance of bubbles on the surface of a kettle of boiling tar.
		Carpenter (1888) interpreted Devils Tower to represent a volcanic plug, being the duct through which the subterranean magmas passed to higher level in the earth's crust.
		The mechanics of the jointing of igneous rocks forbids such a supposition, and we must believe that it represents only a still uneroded fragment whose vertical walls are produced by the columnar structure of a mass which formerly was of much greater lateral extension and possibly of laccolithic form".
	www.cr.nps.gov /history/online_books/berkeley/effinger1/effinger1h.htm (705 words)

	ScienceDaily: Pinatubo Volcano Research Boosts Case For Human-Caused Global Warming
		According to Robock, the eruption on Luzon Island in the Philippines on June 15, 1991 produced the largest volcanic cloud of the 20th century and caused changes in worldwide climate and weather that were felt for years.
		Volcanic Signatures Persist In Oceans (February 9, 2006) -- Ocean temperatures may have risen even higher during the last century if it weren't for volcanoes that spewed ashes and aerosols into the upper atmosphere.
		Stratovolcano -- A stratovolcano is a tall, conical volcano composed of one layer of hardened lava, tephra, and volcanic ash.
	www.sciencedaily.com /releases/2002/02/020220075850.htm (1973 words)

	Volcanic History of the Mono Basin
		…there is a range of volcanic cones that attract the eye, not only on account of their height and the symmetry of their curving slopes of light gray lapilli, but also because they form so striking an exception to the prevailing mountain forms in view.
		So perfect are their shapes and so fresh is their appearance that the eye lingers about their summits in half expectation of seeing wreaths of vapor or the lurid light of molten lava ascending from their throats.
		This volcanic chain stretching ten miles north to south and topping 9,000 ft. may be the youngest volcanic mountain range in North America.
	www.monolake.org /naturalhistory/volcanic.htm (526 words)

	NSSH Part 629 - Glossary, N-R \| NRCS Soils (Site not responding. Last check: 2007-10-22)
		It has a gentle slope away from the river and toward the surrounding floodplain, and its highest elevation is closest to the river bank.
		plug [volcanic] - A consolidated crater-filling of lava, the surrounding material of which has been largely removed by erosion leaving an isolated hill or knob.
		Along shores they are lower (< 10 m tall) and contribute to the temporary or permanent formation of a beach berm or a rim of boulders and stones.
	soils.usda.gov /technical/handbook/contents/part629glossary4.html (6313 words)

	History of Piha
		The Waitakere Ranges were formed around 20 million years ago caused by a violent volcanic upheaval under the sea.
		These massive segments of volcanic rock have eroded to become today a dissected volcanic plateau, the eastern most slopes of which are the Waitakere Ranges as we know them today.
		The Waitakeres are home to a few well known geological formations such as the pillow lavas at Maori Bay in Muriwai, Mercer Bay with the highest cliffs in Auckland standing at 300m and Lion Rock of Piha which is a remnant of a volcanic plug.
	www.awoladventures.co.nz /history_of_piha.htm (570 words)

	University of the West Indies - Seismic Research Unit
		They represent the steep inner core ("volcanic plug") of two lava domes after almost all the loose rubbly material that normally aprons lava domes has been removed by efficient erosion due to the wind and the sea.
		Given the complicated volcanic history of southern Saint Lucia and lack of age data it is impossible to predict with certainty when the next magmatic eruption at the Soufrière Volcanic Centre will occur.
		However, prior to the onset of a volcanic eruption there will be precursor signs of activity, such as an increase in the number and intensity of shallow earthquakes.
	www.uwiseismic.com /Islandprof/St.Lucia/ip_slu_faqs.html (814 words)

	[No title]
		A volcanic plug is formed when a volcano becomes extinct and the molten rock in tube that carried the magma from deep in the earth to the crater of the mountain cools and becomes solid igneous rock.
		Usually the rock in the tube is much tougher than the rest of the mountain and as the wind, rain and snow erode the mountain away, the plug becomes exposed.
		One well-known example of a volcanic plug is Ship Rock in New Mexico which towers 1,700 feet above the surrounding plain.
	www.unmuseum.org /devtowergeo.htm (844 words)

	Goemmer Butte - A latite plug
		Breccia, composed of fragments of Cuchara sandstone and latite, is exposed on the south and west sides of the plug where it had erupted from a central fissure or diatreme (Lindsey, 1995).
		Thin dikes of latite extend from the plug and intrude the breccia.
		The dark rock in front of the Spanish Peaks is Goemmer Butte (pronounced "Gimmer"), a volcanic plug that intruded into the Cuchara Formation as part of the Spanish Peak intrusives.
	home.att.net /~sgeoveatch/Goemmer/Goemmer.html (1073 words)

	Preserve Calavera - Calavera Info
		The 513-ft. Mount Calavera is not really a mountain at all but rather a 22 million-year-old volcanic plug.
		A volcanic plug is a mass of volcanic rock that solidified in it's vent and feeding system millions of years ago.
		When the volcano becomes extinct and starts to erode away, the "plug" is all that is left behind.
	www.preservecalavera.org /calavera.html (484 words)

	Mineral Resources - Minfact 27 (Site not responding. Last check: 2007-10-22)
		The Bindook Volcanic Complex is comprised mostly of ancient volcanic ash.
		Towards the end of the Devonian period, after volcanic activity had ceased and the mineral ores had been laid down, the land subsided and was covered by water.
		The outline of the volcanic crater at Yerranderie has not been completely destroyed by erosion and traces of an ancient rim can be seen on aerial photographs of the area.
	www.minerals.nsw.gov.au /prodServices/minfacts/minfact_27 (1717 words)

	Dive Vanuatu (Site not responding. Last check: 2007-10-22)
		This distinctive sombrero shaped island is and ancient volcanic plug.
		Uninhabited but for the ghosts of King Roymata and those who were buried alive with him, the underwater terrain is a mix of drop-offs, sheer cuttings, fantasy caverns and swim-throughs.
		Hat Island is, of course, shaped like a hat, a large sombrero in fact, this because it is an old volcanic plug.
	www.webspin.org /sailawayshared/hat.html (610 words)

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