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Topic: Volcanic dike

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	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.
		A mixture of volcanic ash and gases that moves downhill as a density current in the atmosphere.
		Volcanic necks (also called plug) are usually more resistant to erosion than the material making up the surrounding cone and may remain standing as a solitary pinnacle when the rest of the original structure has eroded away.
	www.amateurgeologist.com /content/glossary/glossary_v.html (868 words)

	Dike (geology) - Wikipedia, the free encyclopedia
		Dikes are usually high angle to near vertical in orientation, but subsequent tectonic deformation may rotate the sequence of strata through which the dike lies so that the latter becomes horizontal.
		Dikes often form as either radial or concentric swarms around plutonic intrusives or around volcanic necks or feeder vents in volcanic cones.
		Pegmatite dikes are extremely coarsely crystalline granitic rocks often associated with late stage granite intrusions or metamorphic segregations.
	en.wikipedia.org /wiki/Dike_(geology) (248 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.
		Dike: A sheetlike body of igneous rock that cuts across layering or contacts in the rock into which it intrudes.
		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.
	volcano.und.nodak.edu /vwdocs/glossary.html (4560 words)

	40Ar/39Ar and K-Ar Geochronology and Tectonic Significance of the Late Cretaceous Adel Mountain Volcanics and Spatially ...
		Unambiguously post-tectonic dikes (47.5 Ma) that cut all deformed rocks and structures in the area indicate that disturbed belt deformation had clearly ceased by the early Middle Eocene prior to the onset of widespread crustal extension in this part of the northern Cordillera.
		The dikes commonly are resistant to erosion and form prominent linear ridges.
		The dike forms a pronounced topographic ridge and may be a feeder for one of the small laccoliths present east and northeast of the field.
	mason.gmu.edu /~sharlan/adelmountainvolcanics.htm (678 words)

	McHone&Puffer SignificancePaper
		Dikes and basalts across the initial Pangaean rift zone are correlated by radiometric dates near 200 Ma, stratigraphy of associated basin sediments, and chemical characteristics.
		Because diabase dikes and sills are locally prominent in Triassic strata that underlie the basin basalts, stratigraphic and tectonic models have commonly assumed that the basaltic lavas originated from vents within each basin.
		Diabase dikes of the Mesozoic basins are also members of large dike swarms that are characterized by particular orientations and/or magma types, which are found across regions widely separated from the modern basins.
	www.auburn.edu /academic/science_math/res_area/geology/camp/McHone_Puffer.html (5991 words)

	EVALUATION OF THE THREAT OF MEGA TSUNAMI GENERATION FROM POSTULATED MASSIVE SLOPE FAILURES OF ISLAND STRATOVOLCANOES ON ...
		Dike and cryptodome intrusion, as well as hydrothermal alteration in the crater area, probably weakened and further triggered the flank collapse of the Roque Nublo stratovolcano on Gran Canaria Island during the Pliocene period (Mehl and Schmincke, 1999).
		In all cases, forced injection of dikes and kryptodomes - and the concurrent development of mechanical and thermal pore fluid pressures - appear to result in seaward movement of the volcanic flank and may eventually result in partial failures of larger scales.
		Slope failures from the volcanic explosions of Krakatau in 1883 and Santorin in 1490 B.C. : The violent colossal and super-collosal, Plinian and Ultra-Plinian, volcanic explosions of Krakatau in 1883 and of Santorin in 1490 B.C. resulted in large caldera and flank collapses.
	www.drgeorgepc.com /TsunamiMegaEvaluation.html (11982 words)

	HA 730-N Hawaii Oahu regional aquifer system text
		The surface of the Waianae Volcanics consists of soil, saprolite, and pyroclastic material of low permeability that separates the two volcanic-rock aquifers and causes a discontinuity in ground-water levels between the aquifers.
		Likewise, northeast-trending dikes within the southeastern Oahu area create a barrier that causes water levels to be about 7 to 8 feet higher in the western part of the area than in the eastern part (fig.
		The Waianae Volcanics forms the principal aquifer in the area; locally, consolidated sedimentary deposits are minor aquifers, but, for the most part, these deposits have low permeability and confine water in the underlying volcanic-rock aquifer near the coast.
	capp.water.usgs.gov /gwa/ch_n/N-HItext3.html (2670 words)

	Molten Core Model for Hawaiian Rift Zones
		Dike intrusion slowed during the 1983-91 Pu'u O'o eruption sequence, because inflation of the magmatic system -- the engine of intrusion and flank slip processes -- was retarded by continuous magma loss via the molten ERZ core to a low-elevation vent site.
		Thus both the deep and shallow dikes are intruded subvertically from the molten core into regions less favorable to dike intrusion, corresponding to the limbs of the dike-trapping stress curve (Fig.
		A dike injection event of either type will remove magma from the rift-zone core and summit reservoir, lowering the pressure of the magmatic system and, hence, diminishing the likelihood of another event until pressure is restored by mantle resupply.
	www.volcanic.com /library/jvgr/jvgr.html (5117 words)

	What is the difference between a volcanic pipe and a volcanic dike? (Site not responding. Last check: )
		What is the difference between a volcanic pipe and a volcanic dike?
		A pipe refers to magma that cooled in the circular vent (throat) of a volcano.
		A dike is a tabular body (shaped like a book) of magma or rock that cuts across pre-existing rock.
	volcano.und.edu /vwdocs/frequent_questions/grp9/question2489.html (58 words)

	Gulf of Guinea Islands Biodiversity Project
		Although technically not an island, the volcanic peak of Mt. Cameroon along the West African coast is a geological and biological part of this island group.
		The high volcanic peaks of Mt. Cameroon, Bioko, and Sao Tome contain some of the largest areas of this temperate climate in West Africa, and yet the plants and animals are relatively unknown.
		A volcanic dike on Sao Tome which created this distinctive landform when the softer surrounding rock was worn away.
	www.calacademy.org /research/guinea_islands (1575 words)

	[No title]
		Age determinations for individual volcanic vents are used to estimate temporal recurrence rates of volcanism, sometimes referred to as the intensity of volcanic activity, and to correlate rates of volcanic activity with other factors, such as plate motion, rates of crustal extension, and changes in petrology.
		These alignments and their related structures are used to infer the presence and orientation of subsurface dikes and dike sets, as indicators of crustal stress orientation, and to infer mechanisms of shallow dike injection in active volcanic areas (Figure 7).
		Faults and dikes are further interrelated because faulting and dike injection play a similar role in accommodating crustal stress, by slip in the case of faults and increased total crustal volume in the case of dikes.
	www.cas.usf.edu /~cconnor/hazards/art4/art4.html (4263 words)

	IODP Expeditions 309 and 312 Scientific Prospectus
		The dike–gabbro transition and the uppermost plutonic rocks are assumed to be the frozen axial melt lens and the fossil thermal boundary layer between magma chambers and vigorous hydrothermal circulation.
		Drilling the sheeted dike complex at Site 1256 will enable evaluation of whether such faulting and fracturing in tectonic exposures are representative of oceanic crust or whether they may be related to their tectonic setting.
		Most dikes in sheeted dike complexes in tectonic exposures of crust generated at intermediate and fast spreading rates and in Hole 504B in intermediate-rate crust generally dip away from the spreading axis, suggesting tectonic rotation of crustal blocks (Karson, 2002).
	iodp.tamu.edu /publications/SP/309312SP/prosp6.html (1241 words)

	Main Section 4.3.2 to 4.6.2
		Although scientists cannot predict future volcanic activity with total certainty, the resulting data provide a comprehensive basis for estimating the probability of future volcanic activity and for determining the effects on people and the environment if volcanic activity were to disrupt the potential repository (CRWMS MandO 2000f, Section 3.1).
		Basaltic volcanism began during the latter part of the caldera-forming phase, as rates of extension of the earth's crust waned; small-volume basaltic volcanism continued in the Quaternary Period (the past approximately 2 million years).
		Indirect effects that result from volcanic activity outside the repository (e.g., changes to the hydrologic and mineralogical properties of the rock or alteration of water flow and transport) have such low consequences that they are not evaluated further (CRWMS MandO 2000ex).
	www.ocrwm.doe.gov /documents/ser_b/main4c.htm (18824 words)

	Field Trip to Mars - Types of Volcanoes
		A caldera is a large volcanic depression, commonly circular or elliptical when seen from above, caused by a volcano collapsing into itself.
		The eruption of Mount St. Helens in 1980 was caused in part by a lava dome shifting to allow explosive gas and steam to escape from inside the mountain.
		A vent that releases volcanic gases and steam.
	www.kidscosmos.org /kid-stuff/mars-trip-volcanoes-types.html (741 words)

	PRR-03276 dike (Site not responding. Last check: )
		dike, fl, fine grained, slightly silicic, quartz porphyry, slightly epidotized in places
		Irregular dike intruding dacite parallel to shear zone.
		Dike is related to volcanics, not Cretaceous plutons.
	www-bprc.mps.ohio-state.edu /rr/samples/exhibit1/e15128a.htm (62 words)

	[No title]
		Six dikes radiate from a point just west of the central intrusion, the three largest are 9, 4, and 3 km in length and trend S12 degrees E, N80 degrees W, and N55 degrees E respectively.
		Each dike segment is oriented somewhat differently from adjacent dike segments, and the pattern as a whole is not strictly en echélon.
		As is common with breccias within many volcanic necks, the mixture of comminuted sandy host material and juvenile material is some extreme in the breccias that it is often difficult to distinguish sedimentary and volcanic materials on a hand specimen basis.
	www.nmmnh-abq.mus.nm.us /nmmnh/volcanoes/Shiprock.html (794 words)

	CVO Menu - America's Volcanic Past - Connecticut
		The Higganum dike at Exit 9, Route 9 is the root of a huge volcanic fissure eruption that produced a flood basalt 200 million years ago.
		This transition of rock types is due to a dike, which is a sheetlike body of igneous rock that cuts across layering or contacts in the rock into which it intrudes.
		This particular dike is composed of diabase, a fine-grained igneous rock that cooled rapidly near the earth's surface.
	vulcan.wr.usgs.gov /LivingWith/VolcanicPast/Places/volcanic_past_connecticut.html (5081 words)

	Technique may help predict volcanic activity: 11/99
		Geophysicists have been able to construct a moving image of a molten-rock-filled dike buried off the coast of Japan -- a technique that could prove better than current methods for predicting volcanic eruptions.
		No volcanic eruption reached the surface of the sea floor, but lava flowed into the dike at a peak rate of almost 2 million cubic meters per day, Segall said.
		Volcanic dikes, however, proved to be the first practical use.
	www.stanford.edu /dept/news/report/news/1999/november3/magmaimage-113.html (543 words)

	IGNEOUS ROCKS AND VOLCANOES
		The steepness of slopes on a volcanic mountain is determined primarily by:
		Volcanic or extrusive igneous rocks form by the cooling and crystallization of lava flows and the
		Volcanic ash has nothing to do with burning; it is nothing more than pulverized rock.
	www.uwgb.edu /dutchs/Exams/202EXAMS/volcign1.htm (1833 words)

	William Stavast (Site not responding. Last check: )
		Magmatic sulfides concentrations in dikes from the Tintic and Bingham districts were up to 2000 ppm in quenched margins and relatively low (<20 ppm) in the dike centers.
		Volcanic rocks and larger plutons have magmatic sulfides of up to 20 ppm.
		The unusually high concentration in dike margins is attributed to the quenching of the margins allowing for the preservation of magmatic sulfides.
	www.geo.arizona.edu /~wstavast (243 words)

	VOLCANOES
		dikes are mostly of gabbro, sills are diorite
		It was swept away by a volcanic sea wave.
		Although volcanic ash is most widely mentioned in news reports, the most significant global effects of volcanic eruptions are actually produced by:
	www.uwgb.edu /dutchs/Exams/EarthSC102Exams/102Volcano.HTM (1236 words)

	Ocean Drilling Program: Leg 206 Preliminary Report
		Samples of basalt, dikes, gabbros, and peridotites have been retrieved by dredging and from shallow drill holes from most of the ocean basins, but the geological context of these samples is rarely established.
		A second objective is to understand the interactions between magmatic and alteration processes, including the relationships between extrusive volcanics, the feeder sheeted dikes, and the underlying gabbroic rocks from the melt lens and subjacent sills/intrusions.
		The lowermost dikes and upper gabbros have been identified as both the conductive boundary layer between the magma chambers and the axial high-temperature hydrothermal systems and the subsurface reaction zone where downwelling fluids acquire fl-smoker chemistries (Alt et al., 1996; Vanko and Laverne, 1998).
	www-odp.tamu.edu /publications/prelim/206_prel/prel5.html (2288 words)

	BSSA, Volume 87:3 (Site not responding. Last check: )
		This zone has been identified as the site of a seafloor volcanic eruption, dike injection, and large-scale hydrothermal venting or ``megaplume'' event that occurred during 1986 and 1987.
		A possible mechanism for earthquake production might be tectonic release of stress acquired during the dike injection, either along the dike zone or along the bounding faults of the rift valley.
		A fourth event was located southeast of the linear hydrothermal venting and dike injection zone, at a depth coincident with the spreading center crustal melt zone.
	www.seismosoc.org /publications/BSSA_html/bssa_87-3/96067.html (291 words)

	Vic Camp - fissure eruptions
		Dikes are tabular in shape, and they cut discordantly across adjacent rock layers.
		Dikes are often recognized by glassy selvages that develop along their margins where they cool rapidly against the rocks that they intrude, and by contractural cooling joints that generate columnar jointing parallel to their cooling surface, as demonstrated by the two dikes shown here from the Deccan flood basalt province.
		The dike is one of a swarm of E-W to ENE-WSW dikes in the central Deccan flood basalt province.
	www.geology.sdsu.edu /how_volcanoes_work/Fissure.html (940 words)

	Mars Odyssey Mission THEMIS: Feature Image: Galaxias Fossae: The Fire Below
		They were cut by flowing water released in the wake of gigantic flows of ash and lava, while Galaxias appears to have been born in a different way.
		A dike is the name geologists give to a ribbon of molten rock that forces its way into a vertical crack in the crust and widens it.
		If this theory is right, Galaxias reflects the volcanic activity of Elysium, but it illustrates a different eruptive style than most of the region does.
	themis.asu.edu /features/galaxiasfossae (838 words)

	Crater Lake NP: Historic Resource Study (Site not responding. Last check: )
		Examination shows the layers of volcanic conglomerate and lava of which, like layers of brick and stone, the great structure was built.
		A dike formed by molten lava that squeezed into cracks and then solidified, it has been left standing by the erosion of the surrounding material.
		The "sails" are remnants of a volcanic dike from a smaller mountain pre-dating Mazama, making this the oldest lava exposed in the caldera.
	www.nps.gov /crla/hrs/hrs5b.htm (1301 words)

	300 Igneous Activity (Site not responding. Last check: )
		Dike - a sheet-like, cooled intrusion that while hot was injected into a crack that cut across the layering in the surrounding rocks.
		Volcanic neck - a pipe-like, cooled intrusion that while hot was injected into a cylindrical vent leading to a volcano.
		Volcanic bombs - Formed from molten lava that has been blown into the air by an explosive eruption and cooled into a spindle shape while in flight.
	www.csun.edu /geology/Class_Notes/ES300/300ignact.html (1074 words)

	Working Models Relating Hydrothermalism to Volcanic and Tectonic Activity
		Dike injections and fissure eruptions from the melt lens have two important effects.
		In this scenario, cycling between volcanic, tectonic and hydrothermal processes is rapid, and the hydrothermal activity is dominated more by volcanic, than by tectonic, processes.
		Volcanic eruptions are intermittent and widely dispersed, and are coupled in time to injection events of magma from the mantle.
	www.agu.org /revgeophys/humphr01/node6.html (536 words)

	Makushin - Bibliography
		Fault and volcanic dike orientations of the Makushin Volcano region of the Aleutian arc 2496
		Reeder, J. W., 1984, Fault and volcanic dike orientations of the Makushin Volcano region of the Aleutian arc [abs.]: in International Symposium on Recent Crustal Movements of the Pacific Region, Wellington, New Zealand, p.
		Roach, A. L., 1997, Crystal clots in the flank vents and lavas of the Makushin volcanic field: implications for cumulate entrainment: University of Alaska Fairbanks unpublished M.S. thesis, 126 p.
	www.avo.alaska.edu /volcanoes/volcbib.php?volcname=Makushin&sort=date (9725 words)

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