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Topic: Triple junction

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In the News (Sun 16 Jun 19)

  Triple junction - Wikipedia, the free encyclopedia
A triple junction is the point where the boundaries between three tectonic plates, and three plate margins, meet.
The junction of the Red Sea, the Gulf of Aden and the Great Rift Valley of East Africa centered in the Afar Triangle is often given as an example of a triple junction.
Another useful simplification is that the kinematics of triple junctions on a flat Earth are essentially the same as those on the surface of a sphere: despite describing plate motions as involving relative rotations about poles and plate motions on a flat surface being defined by vectors.
en.wikipedia.org /wiki/Triple_junction   (653 words)

 Main Heading Goes Here   (Site not responding. Last check: 2007-10-21)
The point that is at the junction between plates A, B and C  (junction of the trench and the two transform faults is a triple junction.
It is impossible to keep the triple junction on all three boundaries with time as can be shown when plotting the potential triple junction migration vectors of all boundaries on the hodograph as shown by the dotted lines in the following hodograph.
It is a transform-transform-subduction triple junction as the Mendocino fracture zone, the San Andreas fault and the subduction zone in the North meet.
www.uni-mainz.de /FB/Geo/Geologie/Geophysik/Lithosphere/Kinematics.htm   (717 words)

 AGU Web Site:Pulling the Rug out From Under California: Seismic Images of the Mendocino Triple Junction Region
Understanding the effects of triple junction migration on the structure of the crust and upper mantle in this region is therefore necessary for reconstructing the geologic evolution of the continental margin of California and accurately assessing seismic hazards associated with the San Andreas fault system and the Cascadia subduction zone.
North of the triple junction (Figure 2a), the new data indicate that the crust of the Gorda plate lies above both layers of seismicity: it is about 10 km beneath the deformation front and dips about 7° to the east beneath the continental margin.
South of the triple junction (Figure 2b), the lower crust is anomalously reflective in the region where the slabless window is predicted by other investigative methods.
www.agu.org /sci_soc/trehu.html   (2816 words)

 Pulling the Rug Out from under California   (Site not responding. Last check: 2007-10-21)
South of the triple junction (figure 2b, figure 2b_gif), the lower crust is anomalously reflective in the region where the slabless window is predicted by other observations.
The thickest crust is found in the triple junction region (figure 2c, figure 2c_gif), as previously noted by Verdonck and Zandt (1994) based on local earthquake tomography.
South of the triple junction, Franciscan rocks are underlain by the material that generates the high-amplitude reflections discussed in the previous paragraph.
quakes.oce.orst.edu /papers/mendocino.eos/eos.html   (3214 words)

 GEOL C15-0 Supplementary Material
If the the triple junction can be characterized by a velocity, as a discrete entity, it must be characterized by a point in the velocity triangle diagram common to velocities of all three of its component parts.
Thus, the velocity of the triple junction is represented by the intersection of the three lines representing the velocities of the three plate boundaries.
Hence, this triple junction is stable, with the velocity given by the point marked J.
tlacaelel.igeofcu.unam.mx /~GeoD/estudiantes/rosa/puntriple/puntri.html   (984 words)

 triple - Search Results - MSN Encarta
Triple Entente, name given to the diplomatic and military alliance that developed between Britain, France, and Russia in the late 19th and early...
Triple Time, in music, a meter in which the bar may be divided into three beats, as in 3/4 and 9/8.
Rarely, a group of three plates, or a combination of plates, faults, and trenches, meet at a point called a triple junction.
encarta.msn.com /encnet/refpages/searchdetail.aspx?q=triple&pg=1&grp=art   (336 words)

 Seismicity 1980-86: Mendocino Triple Junction
North of this triple junction, oblique subduction dominates, with the eastern margin of the Gorda plate (the southernmost section of the Juan de Fuca plate) slipping beneath the North American plate north-northeastward at a rate of 30 to 50 mm/yr (Wilson, 1986).
South of the triple junction, the Pacific plate is moving past the North American plate along the San Andreas transform boundary on a heading of 35°-38° W. of N. at a rate of approximately 50 mm/yr (DeMets and others, 1987).
The three-dimensional aspects of this triple junction seismicity are illustrated by four cross sections (Figure 5.5B and Figure 5.5C).
www.johnmartin.com /earthquakes/eqsafs/safs_515.htm   (1007 words)

 Triple Plate Junction :: Gold and Mineral Exploration in Vietnam and Papua New Guinea
Triple Plate Junction Plc (AIM : TPJ), is pleased to announce that further exploration at its Otibanda discovery in PNG has revealed another major structure 2 kilometres south of and parallel to the initial Otibanda structure where the Company has already reported consistently high gold and silver values in reconnaissance work.
Triple Plate Junction Plc (AIM : TPJ), is pleased to announce that new rock-chip assays received from first-phase reconnaissance work at the Company’s Otibanda prospect in PNG have produced widespread, consistently high gold values from outcropping quartz veins within strong structural shear zones.
Triple Plate Junction Plc (AIM : TPJ), is pleased to announce that it has secured for a limited royalty payment two small scale copper mining leases in the Zambian copper belt through its new subsidiary, Triple Plate Junction (Africa) Limited The contract is subject to regulatory approval in Zambia.
www.tpjunction.com   (286 words)

 SOPAC - Southern Pacific Tectonics, USGS WCMG   (Site not responding. Last check: 2007-10-21)
The Chile triple junction region is one of only two presently active examples of a ridge/trench collision, an event that has occurred numerous times around the convergent margins of the Pacific basin, most notably along the California continental margin between about 24 million years ago and the present.
This difference is the result of active subduction accretion south of the triple junction and active subduction erosion at and north of the triple junction.
The Chile Margin triple junction is the best modern example of the subduction of an active spreading ridge at a continental subduction zone, and thus is as close as the modern world offers to what happened along the west coast of North America over the last 20 million years of so.
walrus.wr.usgs.gov /research/sopac.html   (2433 words)

 The Mendocino Triple Junction, webpage by Scot Bilbro
In the area that the junction passed 10 million years ago the heat flow and thickness of crust are more normal; this trend continues: the further south, the more normal.
According to the geometry of the interacting plates at the triple junction, whenever the junction migrates north a section of the North American plate that was previously on top of the subducting Juan de Fuca plate slides off, leaving a window without an underlying slab(or plate).
This would account for the high heat flow and shallowness of the area behind the triple junction, but not for the thickness of crust north of the junction or the decreasing trend in the abnormalities further south.
www.coloradocollege.edu /Dept/GY/faculty/wphillips/ScotBilbro.htm   (913 words)

 Heat flow signature key to understanding triple junction dynamics
Recent seismic studies indicated that the crust at the Mendocino Triple Junction was nearly twice as thick as that north and south of the area.
According to the researchers, near the triple junction and north of it, there are heat flows that are quite low.
With the crustal conveyor model, thinning south of the triple junction produces a rise in heat flow because with thinning, the hot areas are closer to the surface.
www.eurekalert.org /pub_releases/2002-01/ps-hfs011002.php   (781 words)

 Gravity and Magnetic data: MENDOCINO TRIPLE JUNCTION
Our general model for the history of this triple junction is one of successive eastward jumps, with sustained periods at each position while significant strike-slip motion occurred on the various transform fault systems, including the San Andreas fault.
The triple junction is interpreted to have been subsequently situated at the north end of the proposed Pilarcitos fault extension and then to have jumped eastward a minimum of about 100 km to the present San Andreas fault trace at what is now approximately lat 38°20' N. on the North American plate.
The eastward jump of the triple junction appears to be associated with a change in stress orientations in this region.
www.johnmartin.com /earthquakes/eqsafs/safs_936.htm   (1677 words)

 geodynamics of mendocino triple junction   (Site not responding. Last check: 2007-10-21)
As the North American crust interacts with the Migrating Mendocino Triple Junction, the crust is first significantly thickened and then equivalently thinned over a distance of a few hundred kilometers (within a time frame of 5 Ma or less).
This process of ephemeral crustal thickening is proposed to result from viscous coupling between the northward migrating Gorda (Juan de Fuca) slab and the base of North America south of the triple junction.
South of triple junction asthenospheric mantle upwells to fill space vacated by migrating Gorda Slab.
www.geodyn.psu.edu /research/americas/egs99/background.html   (213 words)

The data painted a clear picture of the stresses in the region of the triple junction, which are dominated by the motions of the Gorda plate, Schwartz found.
Toward the triple junction, where the Pacific plate ends, the Gorda plate dives under both the North American plate and a corner of the Pacific plate.
At the triple junction (*), the Gorda plate subducts beneath both the North American plate (overlying, not shown) and a corner of the Pacific plate.
www.ucsc.edu /news_events/press_releases/archive/94-95/12-94/12294-Aftershocks_expose_p.html   (1067 words)

 On Shaky Ground 2 Why
Geologists and seismologists find this region of special interest because of the Mendocino triple junction, a place where three plates, the Gorda, the North American and the Pacific, are in contact.
South of the triple junction, the Pacific plate moves northwest relative to the North American plate.
North of the triple junction, the Gorda plate and its northern extension, the Juan de Fuca plate, move eastward on a collision course with the North American plate.
www.humboldt.edu /~geology/earthquakes/shaky2_why.html   (846 words)

 OceanDocs: Item 1834/740
The Rodriguez Triple Junction (RTJ) is a junction connecting three mid-ocean ridges in the Indian Ocean: the Southwest Indian Ridge (SWIR), the Central Indian Ridge (CIR) and the Southeast Indian Ridge (SEIR).
The evolution of the RTJ has been studied extensively for the past 10 Ma and the triple junction is believed to be largely a ridge-ridge-ridge (RRR) triple junction.
Because the RRR triple junction is the most stable configuration that is possible, it is suggested that the configuration of the RTJ has been largely RRR triple junction since its formation.
iodeweb1.vliz.be /odin/handle/1834/740   (237 words)

Uni-Solar is immune from this problem because the amount of SGS or solar grade silicon used in Uni-Solar triple junction is miniscule compared to old fashioned crystal silicon PV panels.
The secret is glass free construction and United Solar Systems patented Triple Junction Technology which combines three separate tuned PV layers for red,green and blue light.
Triple Junction Technology provides the most solar power per purchased watt in the PV industry.
smartroofsystems.com /index.html   (1321 words)

 Triple Junctions (via CobWeb/3.1 planetlab2.tamu.edu)   (Site not responding. Last check: 2007-10-21)
A triple junction is a point which lies at the intersection of three plate boundaries
To discuss what happens at triple junctions, we will consider a flat Earth; such an approximation is justified if we limit ourselves to the area adjacent to the triple junction.
A triple junction is said to be stable when the relative motions of the three plates and the azimuth of their boundaries are such that the configuration of the junction does not change with time.
wwwrses.anu.edu.au.cob-web.org:8888 /~jean/GEOL3005/PlateTectonics/Triple.html   (346 words)

 LiveScience.com - Some Good Earthquake News: Fault Mellows with Age
The Triple Junction is where the Juan de Fuca plate, the North American plate and the Pacific plate converge in an area off the Pacific Northwest coast from Oregon to Vancouver Island.
But the junction's newfound reorganization could indicate that the "subduction," or sinking under, of the Juan de Fuca plate beneath the North American Plate is slowing down or eventually cease all together, the researchers say.
The Triple Junction's transition from a subduction zone to one of slips could reduce the chances that huge earthquakes of magnitude 9.0 or higher will occur in the region, Dziak said.
www.livescience.com /forcesofnature/060417_triple_junction.html   (513 words)

 Rewritten geological history alters view of California earthquakes
The Mendocino Triple Junction is where the North American, Pacific and Gorda plates come together.
According to Furlong, that may be because the thickening and thinning process obscure the end and the fault is only clearly seen in areas where the triple junction has already passed.
North and south of the area immediately affected by the triple junction, the rivers flow north and south respectively, but between the two raised areas, rivers tend to meander and turn back on themselves, complicating flood prediction and protection.
www.eurekalert.org /pub_releases/1999-12/PS-Rgha-141299.php   (876 words)

 Triple Junction Motion for Faceted Interfaces
In the absence of triple junctions, the quantity to be minimized in the time-stepping procedure outlined in equation 19 becomes
coming into the triple junction has its other endpoint at another triple junction, then the motion of the three segments is decoupled from that of all the other segments but coupled to each other.
In case the surface energy functions for all the interfaces do satisfy that particular relationship, then this variational formulation is inadequate to determine the triple junction position.
www.ctcms.nist.gov /~wcraig/variational/node13.html   (1205 words)

 Atna Resources Ltd. - Dixie Fork - Triple Junction - Fri Dec 8, 2006
Atna's Triple Junction and Dixie Fork projects are Carlin type sediment-hosted prospects located at the south end of the prolific Carlin Trend.
The Triple Junction property is in a structural and geological setting similar to the Rain deposit.
The mineralized area is characterized by strong argillic and silica alteration, enriched in arsenic and barite and cut by felsic dikes typical of Carlin-type deposits.
www.atna.com /s/DixieFork.asp   (384 words)

 d09 Rift valleys and triple junctions (via CobWeb/3.1 planetlab2.tamu.edu)   (Site not responding. Last check: 2007-10-21)
This results in three rift valleys and associated ridges, which radiate with a T or a Y map pattern from the common point (triple junction).
The triple junction, unlike a hotspot, is not fixed but moves in the direction of nearest subduction.
In the case of a triple junction in a continental plate, two branches widen to form oceanic plates and one branch becomes a graben (but does not separate enough to open a deep ocean).
geowords.com.cob-web.org:8888 /histbooknetscape/d09.htm   (553 words)

 Integrated Engineering
In the sample case to the left the "triple junction" is a dielectric (left), air (right) and an electrode (bottom).
You cannot ask what is the direction of the field at the junction - that depends on the direction from which you approach it.
The spatial resolution of E in both cases is approximately the local size of the elements.
www.integratedsoft.com /papers/benchmark/triple_junction   (1031 words)

 Plate Tectonics: GEOLOGY LAB
A number of triple junction diagrams are shown below.
Your job is to determine the type of triple junction that is shown.
Unless otherwise noted, all images and graphics contained within are the property of Richard Harwood and may only be reproduced with permission from the author.
facweb.bhc.edu /academics/science/harwoodr/Geol101/labs/PlateTectonics2/index.htm   (126 words)

 junction - Search Results - MSN Encarta
Junction City, city, seat of Geary County, north central Kansas.
Its name derives from its location at the junction of the Republican and Smoky Hill...
Grand Junction, city, seat of Mesa County, western Colorado, at the junction of the Gunnison and Colorado rivers (hence its name); settled 1881,...
encarta.msn.com /encnet/refpages/search.aspx?q=junction   (160 words)

 Triple Junction Stability   (Site not responding. Last check: 2007-10-21)
It contains analyses of the Indian Ocean triple junction and the Gulf of California triple junctions.
Some scientists think the Eurasian--North American plate boundary is west of its location on the map in MICRODEM (for instance Map of the plates), and that this triple junction is actually Philippine--Pacific--North America.
Is the triple junction stable, and if so, will it be migrating.
www.usna.edu /Users/oceano/pguth/website/so461web/triple_junctions.htm   (364 words)

 Tectonics of the Azores (via CobWeb/3.1 planetlab2.tamu.edu)   (Site not responding. Last check: 2007-10-21)
The Azores are shown as hot spot volcanoes on some maps but physical and chemical evidence shows they are associated with a spreading center.
Searle (1980) presented an excellent study on the history of the Azores triple junction, the area where the North American (shown as N.A. Plate), Eurasian, and African plates meet at a point.
Triple junctions can have any shapes but "T" or "Y" shapes are most common.
volcano.und.nodak.edu.cob-web.org:8888 /vwdocs/volc_images/africa/azores/tectonics.html   (263 words)

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