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45-686: Euripus or Euripo ( s ) can refer to: Euripus Strait in Central Greece, between Euboea and the main Greek peninsula Chalcis , a town located on that strait, also known in the Middle Ages as Euripus Euripus (Acarnania) , an ancient city in Acarnania, Greece Euripus (genus) a genus of butterflies Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with

90-547: A Veronese or Venetian joke, or folk-etymological corruption or re-interpretation in reference to the old bridge across the channel.) In 1395, Nicola di Martoni came to Negropont during the return from his pilgrimage to Egypt and Palestine. He is clear that the main shipping channel in the Venetian period was on the side of the Boeotian mainland, and mentions the mills on the narrower channel, which he says were sometimes broken in

135-438: A central volcano or intrusion. Though they appear to originate in the central intrusion, the dikes often have a different age and composition from the intrusion. These radial swarms may have formed over the intrusion and were later cut by the rising body of magma, or the crust was already experiencing regional tension and the intrusion triggered formation of the fissures. In rock of the oceanic crust, pillow lava erupted onto

180-460: A curtain of fire where lava erupts along the entire length of a fissure several kilometers long. However, the length of erupting fissure diminishes over time, becoming focused on a short segment of less than half a kilometer. The minimum possible width of a dike is determined by the balance between magma movement and cooling. There may be more than one injection of magma along a given fissure. When multiple injections are all of similar composition,

225-413: A dike or dyke is a sheet of rock that is formed in a fracture of a pre-existing rock body. Dikes can be either magmatic or sedimentary in origin. Magmatic dikes form when magma flows into a crack then solidifies as a sheet intrusion , either cutting across layers of rock or through a contiguous mass of rock. Clastic dikes are formed when sediment fills a pre-existing crack. A magmatic dike

270-534: A rotating one in 1896. The existing, originally wooden bridge was built in 1962 and was extensively refurbished in 1998. The Euripus was closed by a dike of coarse sediment until about 6000 years ago, when it was opened by an (unrecorded) earthquake. Herodotus mentions the strait during his description of the Battle of Artemisium (480 BC), with the account implying that it was navigable by large fleets of triremes . Diodorus Siculus reports that in 411 BC

315-489: A sill is a sheet intrusion that forms within and parallel to the bedding. Mafic magma (fluid magma low in silica) usually reaches the surface through fissures, forming dikes. At the shallowest depths, dikes form when magma rises into an existing fissure. In the young, shallow dikes of the Hawaiian Islands, there is no indication of forceful intrusion of magma. For example, there is little penetration of magma into

360-425: A consequence of the direction of minimum principal stress changing as the magma ascends from deep to shallow levels in the crust. An en echelon dike set may evolve into single dike with bridges connecting the formerly separate segments and horns showing former segment overlaps. In ancient dikes in deformed rock, the bridges and horns are used by geologists to determine the direction of magma flow. Where there

405-581: A dike is much smaller than its other two dimensions, and the opposite walls are roughly parallel, so that a dike is more or less constant in thickness. The thickness of different dikes can range from a few millimeters to hundreds of meters, but is most typically from about a meter to a few tens of meters. The lateral extent can be tens of kilometers, and dikes with a thickness of a few tens of meters or more commonly extend for over 100 km. Most dikes are steeply dipping; in other words, they are oriented nearly vertically. Subsequent tectonic deformation may rotate

450-473: A galley to pass through at some time in the late 16th century, and was still just barely wide enough at the time of his visit in 1668 for a galley to squeeze through, even though the old shipping channel had been abandoned. By the end of the 18th century it was well on its way to being the width of the modern channel. 38°27′46″N 23°35′22″E  /  38.46278°N 23.58944°E  / 38.46278; 23.58944 Dike (geology) In geology ,

495-598: A line extending for 250 km. Individual segments overlap, with the overlapping portions thinner, so that the combined thickness of the two overlapped portions is about the same as the thickness of a single segment. Other examples of en echelon dikes are the Inyo dike of Long Valley, California , US; the Jagged Rocks complex, Arizona , US; and the dikes of oceanic spreading centers . Dikes range in composition from basaltic to rhyolitic , but most are basaltic. The texture

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540-583: A new narrower cleft to the east of it, so narrow that it could be crossed with a single plank of wood. This later stream was later widened to make the present shipping channel. At the time when Procopius wrote, the name of the fortress on the Euripus was probably "Euripus," which had become "Egripos" by 1204, and was adopted and slightly altered to "Nigriponte" by the Latins who occupied the place in 1205. (The name has nothing to do with any sort of "Black Bridge," except as

585-533: A ring fracture. Magma rising into the ring fracture produces a ring dike. Good examples of ring dikes and cone sheets are found in the Ardnamurchan peninsula of Scotland. A feeder dike is a dike that acted as a conduit for magma moving from a magma chamber to a localized intrusion . For example, the Muskox intrusion in arctic Canada was fed by a large dike, with a thickness of 150 meters. A sole injection

630-411: A shallow magma chamber. Cone sheets form when magma is injected into a shallow magma chamber, which lifts and fractures the rock beds above it. The fractures take the form of a set of concentric cones dipping at a relatively shallow angle into the magma chamber. When the caldera is subsequently emptied by explosive volcanic activity, the roof of the magma chamber collapses as a plug of rock surrounded by

675-474: A single ship. There is no mention of the closure of the strait in either Thucydides ' History of the Peloponnesian War or Xenophon 's Hellenica . Strabo wrote that at an unspecified later date the strait was crossed by a bridge two plethra long (approximately 50 m (160 ft), which is probably an exaggeration ). Some vestiges of the artificial dike probably remained, so the gap spanned by

720-441: Is 160 m (525 ft) wide at this point. The bridge is accessible via a fork on the main road at Aulis . The "Old" or "Low" or "Sliding" Bridge lies across midtown, and can slide away to allow shipping traffic. It is located at the narrowest point of the strait, where it is only 38 m (125 ft) wide. It accommodates two lanes of vehicular traffic. It was originally built as a retractable bridge in 1858, replaced by

765-474: Is a sheet of igneous rock that cuts across older rock beds. It is formed when magma fills a fracture in the older beds and then cools and solidifies. The dike rock is usually more resistant to weathering than the surrounding rock, so that erosion exposes the dike as a natural wall or ridge. It is from these natural walls that dikes get their name. Dikes preserve a record of the fissures through which most mafic magma (fluid magma low in silica) reaches

810-457: Is concentrated on the tip of the propagating fracture. In effect, the magma wedges apart the brittle rock in a process called hydraulic fracture . At greater depths, where the rock is hotter and less brittle, the magma forces the rock aside along brittle shear planes oriented 35 degrees to the sides of the dock. This bulldozer-like action produces a blunter dike tip. At the greatest depths, the shear planes become ductile faults, angled 45 degree from

855-593: Is even more precarious because of vortex formation. The Swiss scholar François-Alphonse Forel contributed to an understanding of the enigmatic phenomenon by his study of limnology and the discovery of seiche , where layers of water of differing temperature oscillate in thickness in a confined body of water. But the problem was solved completely only by D. Eginitis, director of the Athens Observatory, who published his conclusions in 1929. From Ancient Greek εὔριπος (eúrīpos, "any strait or narrow sea, where

900-408: Is rapid flow of molten magma through a fissure, the magma tends to erode the walls, either by melting the wall rock or by tearing off fragments of wall rock. This widens the fissure and increases flow. Where flow is less rapid, the magma may solidify next to the wall, narrowing the fissure and decreasing flow. This causes flow to become concentrated at a few points. At Hawaii, eruptions often begin with

945-465: Is subject to strong tidal currents which reverse direction approximately four times a day. Tidal flows are very weak in the Eastern Mediterranean , but the strait is a remarkable exception. Water flow peaks at about 12 kilometres per hour (7.5 mph; 6.5 kn), either northwards or southwards, and lesser vessels are often incapable of sailing against it. When nearing flow reversal, sailing

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990-555: Is the Mackenzie dike swarm in the Northwest Territories , Canada. Dike swarms (also called dike complexes ) are exposed in the eroded rift zones of Hawaiian volcanoes. As with most other magmatic dikes, these were fissures through which lava reached the surface. The swarms are typically 2.5 to 5 km in width, with individual dikes about a meter in width. The dike swarms extend radially out from volcano summits and parallel to

1035-691: Is the P-wave velocity of the host rock (essentially, the speed of sound in the rock). This formula predicts that dikes will be longer and narrower at greater depths below the surface. The ratio of thickness to length is around 0.01 to 0.001 near the surface, but at depth it ranges from 0.001 to 0.0001. A surface dike 10 meters in thickness will extend about 3 km, while a dike of similar thickness at depth will extend about 30 km. This tendency of intruding magma to form shorter fissures at shallower depths has been put forward as an explanation of en echelon dikes. However, en echelon dikes have also been explained as

1080-415: Is the thickness of the dike; b {\displaystyle b} is its lateral extent; P e x {\displaystyle P_{ex}} is the excess pressure in the magma relative to the host rock; ρ h o s t {\displaystyle \rho _{host}} is the density of the host rock; and V P {\displaystyle V_{P}}

1125-483: Is typically slightly coarser than basalt erupted at the surface, forming a rock type called diabase . The grain size varies systematically across the dike, with the coarsest grains normally at the center of the dike. Dikes formed at shallow depth commonly have a glassy or fine-grained chilled margin 1 to 5 cm thick, formed where the magma was rapidly cooled by contact with the cold surrounding rock. Shallow dikes also typically show columnar jointing perpendicular to

1170-416: Is usually dense, with almost no vesicles (frozen bubbles), but vesicles may be seen in the shallowest part of a dike. When vesicles are present, they tend to form bands parallel to walls and are elongated in direction of flow. Likewise, phenocrysts (larger crystals) on the margins of the dike show an alignment in the direction of flow. In contrast to dikes, which cut across the bedding of layered rock,

1215-457: The Euboeans closed the strait by mostly rebuilding the dike, with the goal of making themselves part of Boeotia, therefore not an island subject to Athenian hegemony. Diodorus states that gaps had to be left in the dike to allow the Euripus tides to flow through; the narrowness of the remaining passage made the current much more intense. Only a single passage was left navigable , just wide enough for

1260-426: The bridge could have been narrower than the channel that existed before 411 BC. Ancient historians do not record the depth of the channel; even the passage under Strabo's bridge may have been scoured by the tides to a depth sufficient for ancient shipping. Procopius reports that during the reign of Emperor Justinian I (527 to 565 AD) there were two channels in the Euripus, the large original channel and

1305-685: The center of the dike. If the previous dike rock has cooled significantly, the subsequent injection can be characterized by fracturing of the old dike rock and the formation of chilled margins on the new injection. Sometimes dikes appear in swarms, consisting of several to hundreds of dikes emplaced more or less contemporaneously during a single intrusive event. Dike swarms are almost always composed of diabase and most often are associated with flood basalts of large igneous provinces . They are characteristic of divergent plate boundaries . For example, Jurassic dike swarms in New England and Paleogene swarms in

1350-476: The center of the rift zone before abruptly dropping to very few dikes. It is likely that the number of dikes must increase with depth, reaching a typical value of 300 to 350 per kilometer at the level of the ocean floor. In some respects, these dike swarms resemble those of western Scotland associated with the flood eruptions that preceded the opening of the Atlantic Ocean. Dikes often form as radial swarms from

1395-438: The dike is described as a multiple dike . However, subsequent injections are sometimes quite different in composition, and then the dike is described as a composite dike . The range of compositions in a composite dike can go all the way from diabase to granite , as is observed in some dikes of Scotland and northern Ireland. After the initial formation of a dike, subsequent injections of magma are most likely to take place along

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1440-507: The flux and reflux is violent"); from εὖ (eû, "well") + ῥιπή (rhipḗ, “swing or force with which anything is thrown”), from ῥίπτω (rhíptō, "to throw"). There are two road bridges across the strait, both at Chalcis. One is the Euripus Bridge or Chalcis Bridge, a two-pylon, cable-suspended bridge built south of town in 1992, and commonly called the "New" or "High" bridge, with a span of about 215 m (705 ft). The strait

1485-415: The long axis of the volcanic shield. Sills and stocks are occasionally present in the complexes. They are abruptly truncated at the margins of summit calderas. Typically, there are about 50 to 100 dikes per kilometer at the center of the rift zone, though the density can be as high as 500 per kilometer and the dikes then make up half the volume of the rock. The density drops to 5 to 50 per kilometer away from

1530-688: The magma fractured and disintegrated the rock at its advancing tip rather than prying the rock apart. Other dikes may have formed by metasomatism , in which fluids moving along a narrow fissure changed the chemical composition of the rock closest to the fissure. There is an approximate relationship between the width of a dike and its maximum extent, expressed by the formula: 2 w 2 b = 2.25 P e x ρ h o s t V P 2 {\displaystyle {\frac {2w}{2b}}={\frac {2.25P_{ex}}{\rho _{host}V_{P}^{2}}}} Here w {\displaystyle w}

1575-401: The margins. Here the dike rock fractures into columns as it cools and contracts. These are usually 5- to 6-sided, but 3- to 4-sided columns are also common. These are fairly uniform in size within a single dike, but range from a few centimeters to over 0.3 meters across in different dikes, tending to be thicker in wider dikes. Larger columns are likely a consequence of slower cooling. Dike rock

1620-431: The rock, always opening a path along a plane normal to the minimum principal stress . This is the direction in which the crust is under the weakest compression and so requires the least work to fracture. At shallow depths, where the rock is brittle, the pressurized magma progressively fractures the rock as it advances upwards. Even if the magma is only slightly pressurized compared with the surrounding rock, tremendous stress

1665-429: The sea floor is underlain by sheeted dike complexes that preserve the conduits through which magma reached the ocean floor at mid-ocean ridges . These sheeted dikes characteristically show a chilled margin on only one side, indicating that each dike was split in half by a subsequent eruption of magma. Ring dikes and cone sheets are special types of dikes associated with caldera volcanism. These are distributed around

1710-527: The sequence of strata through which the dike propagates so that the dike becomes horizontal. It is common for a set of dikes, each a few kilometers long, to form en echelon . This pattern is seen in the Higganum dike set of New England. This dike set consists of individual dikes that are typically four kilometers in length at the surface and up to 60 meters wide. These short segments form longer groups extending for around 10 km. The entire set of dikes forms

1755-560: The sides of the dike. At depths where the rock is completely plastic, a diapir (a rising plug of magma) forms instead of a dike. The walls of dikes often fit closely back together, providing strong evidence that the dike formed by dilatation of a fissure. However, a few large dikes, such as the 120-meter-thick Medford dike in Maine, US, or the 500-meter-thick Gardar dike in Greenland, show no dilatation. These may have formed by stoping , in which

1800-562: The speed and turbulence of the flow there. We have further information about the shipping channel and its single wooden bridge from various documents in the archives of the Venetian Empire . In 1408, the formation of a reef under the bridge severely affected shipping ( http://www.archiviodistatovenezia.it/divenire/collezioni.htm Archived 2016-01-27 at the Wayback Machine Senato, Deliberazioni, Misti . 48,43v) and in 1439 there

1845-465: The surface. They are studied by geologists for the clues they provide on volcanic plumbing systems . They also record ancient episodes of extension of the Earth's crust , since large numbers of dikes ( dike swarms ) are formed when the crust is pulled apart by tectonic forces. The dikes show the direction of extension, since they form at right angles to the direction of maximum extension. The thickness of

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1890-496: The title Euripus . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Euripus&oldid=875548014 " Categories : Disambiguation pages Place name disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Euripus Strait The strait

1935-400: The walls of dikes even when the walls consist of highly porous volcanic clinker, and little wall material breaks off into the molten magma. These fissures likely open as a result of bulging of the rock beds above a magma chamber that is being filled with magma from deeper in the crust. However, open fractures can exist only near the surface. Magma deeper in the crust must force its way through

1980-488: The west of Scotland and running into northern England record the early opening of the Atlantic Ocean. Dike swarms are forming in the present day along the divergent plate boundary running through Iceland. Dike swarms often have a great cumulative thickness: Dikes in Iceland average 3 to 5 meters in width, but one 53-kilometer stretch of coast has about 1000 dikes with total thickness of 3 kilometers. The world's largest dike swarm

2025-403: Was concern over the tendency of the current to erode the surroundings of the pilings that supported the bridge ( http://www.archiviodistatovenezia.it/divenire/collezioni.htm Archived 2016-01-27 at the Wayback Machine Senato, Deliberazioni, Misti . 60,140r–42r). Evliya Çelebi , in his Travel Journal (SN VIII250a27, ff.), tells us that the narrow channel was first opened out enough for

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