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101-748: The Rhenohercynian Zone, named for the Rhine River and the Hercynian Forest of Antiquity, forms a narrow zone through western and central Europe, from Cornwall and Ireland in the west to the Harz mountains of central Germany in the east, including the Rhenish Massif ( Ardennes , Taunus , Eifel and Hunsrück ). The total length of this ancient basin (the Rhenohercynian Basin ) could have been more than 2500 km. In

202-423: A mantle wedge above the descending slab. The slab releases water vapor and other volatiles as it descends, which further lowers the melting point, further increasing the amount of decompression melting. Each tectonic setting produces basalt with its own distinctive characteristics. The mineralogy of basalt is characterized by a preponderance of calcic plagioclase feldspar and pyroxene . Olivine can also be

303-493: A basalt is diagnostic of how and where it erupted—for example, whether into the sea, in an explosive cinder eruption or as creeping pāhoehoe lava flows, the classic image of Hawaiian basalt eruptions. Basalt that erupts under open air (that is, subaerially ) forms three distinct types of lava or volcanic deposits: scoria ; ash or cinder ( breccia ); and lava flows. Basalt in the tops of subaerial lava flows and cinder cones will often be highly vesiculated , imparting

404-518: A deep foreland basin . This filled with the products of erosion in the Hercynian mountains and the contemporaneously uplifted London-Brabant Massif to the north. During the Westphalian, the basin was completely filled and rose above sea level. The Rhenohercynian basin was filled with Devonian and Carboniferous sediments. Sedimentation was often disrupted by tectonic phases , but nevertheless

505-442: A distinctive pillow shape, through which the hot lava breaks to form another pillow. This "pillow" texture is very common in underwater basaltic flows and is diagnostic of an underwater eruption environment when found in ancient rocks. Pillows typically consist of a fine-grained core with a glassy crust and have radial jointing. The size of individual pillows varies from 10 cm up to several metres. When pāhoehoe lava enters

606-413: A domestication that served goals such as reducing stagnant bogs that fostered waterborne diseases, making regions more habitable for human settlement, and reduce high frequency of floods. Not long before Tulla went to work on widening and straightening the river, heavy floods caused significant loss of life. Four diplomatic treaties were signed among German state governments and French regions dealing with

707-427: A flow can shrink in the vertical dimension without fracturing, it cannot easily accommodate shrinking in the horizontal direction unless cracks form; the extensive fracture network that develops results in the formation of columns . These structures, or basalt prisms , are predominantly hexagonal in cross-section, but polygons with three to twelve or more sides can be observed. The size of the columns depends loosely on

808-465: A high content of plagioclase; these are sometimes described as leucobasalts . It can be difficult to distinguish between lighter-colored basalt and andesite , so field researchers commonly use a rule of thumb for this purpose, classifying it as basalt if it has a color index of 35 or greater. The physical properties of basalt result from its relatively low silica content and typically high iron and magnesium content. The average density of basalt

909-621: A lightweight "frothy" texture to the rock. Basaltic cinders are often red, coloured by oxidized iron from weathered iron-rich minerals such as pyroxene . ʻAʻā types of blocky cinder and breccia flows of thick, viscous basaltic lava are common in Hawaiʻi. Pāhoehoe is a highly fluid, hot form of basalt which tends to form thin aprons of molten lava which fill up hollows and sometimes forms lava lakes . Lava tubes are common features of pāhoehoe eruptions. Basaltic tuff or pyroclastic rocks are less common than basaltic lava flows. Usually basalt

1010-623: A lower total content of alkali oxides than trachybasalt and most basanites and tephrites. Basalt generally has a composition of 45–52 wt% SiO 2 , 2–5 wt% total alkalis, 0.5–2.0 wt% TiO 2 , 5–14 wt% FeO and 14 wt% or more Al 2 O 3 . Contents of CaO are commonly near 10 wt%, those of MgO commonly in the range 5 to 12 wt%. High-alumina basalts have aluminium contents of 17–19 wt% Al 2 O 3 ; boninites have magnesium (MgO) contents of up to 15 percent. Rare feldspathoid -rich mafic rocks, akin to alkali basalts, may have Na 2 O + K 2 O contents of 12% or more. The abundances of

1111-947: A mostly northerly direction through the German Rhineland . Finally in Germany, the Rhine turns into a predominantly westerly direction and flows into the Netherlands where it eventually empties into the North Sea . It drains an area of 9,973 km . Its name derives from the Celtic Rēnos . There are two German states named after the river, North Rhine-Westphalia and Rhineland-Palatinate , in addition to several districts (e.g. Rhein-Sieg ). The departments of Bas-Rhin and Haut-Rhin in Alsace (France) are also named after

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1212-507: A phenocryst, and when present, may have rims of pigeonite. The groundmass contains interstitial quartz or tridymite or cristobalite . Olivine tholeiitic basalt has augite and orthopyroxene or pigeonite with abundant olivine, but olivine may have rims of pyroxene and is unlikely to be present in the groundmass . Alkali basalts typically have mineral assemblages that lack orthopyroxene but contain olivine. Feldspar phenocrysts typically are labradorite to andesine in composition. Augite

1313-523: A significant constituent. Accessory minerals present in relatively minor amounts include iron oxides and iron-titanium oxides, such as magnetite , ulvöspinel , and ilmenite . Because of the presence of such oxide minerals, basalt can acquire strong magnetic signatures as it cools, and paleomagnetic studies have made extensive use of basalt. In tholeiitic basalt , pyroxene ( augite and orthopyroxene or pigeonite ) and calcium -rich plagioclase are common phenocryst minerals. Olivine may also be

1414-588: A waterway in the Holy Roman Empire . Among the largest and most important cities on the Rhine are Cologne , Rotterdam , Düsseldorf , Duisburg , Strasbourg , Arnhem , and Basel . The variants of the name of the Rhine (Latin Rhenus; French Rhin, Italian Reno, Romansh Rain or Rein, Dutch Rijn, Alemannic Ry, Ripuarian Rhing) in modern languages are all derived from the Gaulish name Rēnos , which

1515-427: Is 2.9 g/cm , compared, for example, to granite ’s typical density of 2.7 g/cm . The viscosity of basaltic magma is relatively low—around 10 to 10 cP —similar to the viscosity of ketchup , but that is still several orders of magnitude higher than the viscosity of water, which is about 1 cP). Basalt is often porphyritic , containing larger crystals ( phenocrysts ) that formed before the extrusion event that brought

1616-747: Is a Central German development of the early modern period , with the Alemannic name R(n) keeping the older vocalism. In Alemannic, the deletion of the ending -n in pausa is a recent development; the form Rn is largely preserved in Lucernese dialects. Rhing in Ripuarian is diphthongized, as is Rhei, Rhoi in Palatine . While Spanish has adopted the Germanic vocalism Rin- , Italian, Occitan, and Portuguese have retained

1717-401: Is also produced by some subglacial volcanic eruptions. Basalt is the most common volcanic rock type on Earth, making up over 90% of all volcanic rock on the planet. The crustal portions of oceanic tectonic plates are composed predominantly of basalt, produced from upwelling mantle below the ocean ridges . Basalt is also the principal volcanic rock in many oceanic islands , including

1818-417: Is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low- viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon . More than 90% of all volcanic rock on Earth is basalt. Rapid-cooling, fine-grained basalt is chemically equivalent to slow-cooling, coarse-grained gabbro . The eruption of basalt lava

1919-761: Is considered a key to understanding plate tectonics , its compositions have been much studied. Although MORB compositions are distinctive relative to average compositions of basalts erupted in other environments, they are not uniform. For instance, compositions change with position along the Mid-Atlantic Ridge , and the compositions also define different ranges in different ocean basins. Mid-ocean ridge basalts have been subdivided into varieties such as normal (NMORB) and those slightly more enriched in incompatible elements (EMORB). Isotope ratios of elements such as strontium , neodymium , lead , hafnium , and osmium in basalts have been much studied to learn about

2020-481: Is defined as volcanic rock with a content of between 45% and 52% silica and no more than 5% alkali metal oxides. This places basalt in the B field of the TAS diagram. Such a composition is described as mafic . Basalt is usually dark grey to black in colour, due to a high content of augite or other dark-coloured pyroxene minerals, but can exhibit a wide range of shading. Some basalts are quite light-coloured due to

2121-803: Is not well understood, because in many places the Devonian and Carboniferous rock strata are covered with younger deposits. Parts of the basin have their own names, like the Cornwall basin in Cornwall, the Munster basin in Ireland or the Rhenisch basin in Belgium and Germany. The Rhenohercynian Zone is a part of the northern foreland of the Hercynian orogeny. It has a lower grade of metamorphism than

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2222-753: Is observed by geologists at about 20 volcanoes per year. Basalt is also an important rock type on other planetary bodies in the Solar System . For example, the bulk of the plains of Venus , which cover ~80% of the surface, are basaltic; the lunar maria are plains of flood-basaltic lava flows ; and basalt is a common rock on the surface of Mars . Molten basalt lava has a low viscosity due to its relatively low silica content (between 45% and 52%), resulting in rapidly moving lava flows that can spread over great areas before cooling and solidifying. Flood basalts are thick sequences of many such flows that can cover hundreds of thousands of square kilometres and constitute

2323-583: Is rich in titanium compared to augite in tholeiitic basalt. Minerals such as alkali feldspar , leucite , nepheline , sodalite , phlogopite mica, and apatite may be present in the groundmass. Basalt has high liquidus and solidus temperatures—values at the Earth's surface are near or above 1200 °C (liquidus) and near or below 1000 °C (solidus); these values are higher than those of other common igneous rocks. The majority of tholeiitic basalts are formed at approximately 50–100 km depth within

2424-597: Is significantly shortened from its natural course due to a number of canal projects completed in the 19th and 20th century. The "total length of the Rhine", to the inclusion of Lake Constance and the Alpine Rhine is more difficult to measure objectively; it was cited as 1,232 kilometers (766 miles) by the Dutch Rijkswaterstaat in 2010. Its course is conventionally divided as follows: The Rhine carries its name without distinctive accessories only from

2525-784: Is sometimes called Rhinesee ("Lake Rhine"). Besides the Seerhein , the Radolfzeller Aach is the main tributary of Untersee . It adds large amounts of water from the Danube system to the Untersee via the Danube Sinkhole . Reichenau Island was formed at the same time as the Seerhein, when the water level fell to its current level. Lake Untersee is part of the border between Switzerland and Germany , with Germany on

2626-402: Is suppressed. Above this depth, submarine eruptions are often explosive, tending to produce pyroclastic rock rather than basalt flows. These eruptions, described as Surtseyan, are characterised by large quantities of steam and gas and the creation of large amounts of pumice . When basalt erupts underwater or flows into the sea, contact with the water quenches the surface and the lava forms

2727-643: Is the second-longest river in Central and Western Europe (after the Danube ), at about 1,230 km (760 mi), with an average discharge of about 2,900 m /s (100,000 cu ft/s). The Rhine and the Danube comprised much of the Roman Empire 's northern inland boundary , and the Rhine has been a vital navigable waterway bringing trade and goods deep inland since those days. The various castles and defenses built along it attest to its prominence as

2828-440: Is too hot and fluid to build up sufficient pressure to form explosive lava eruptions but occasionally this will happen by trapping of the lava within the volcanic throat and buildup of volcanic gases . Hawaiʻi's Mauna Loa volcano erupted in this way in the 19th century, as did Mount Tarawera , New Zealand in its violent 1886 eruption. Maar volcanoes are typical of small basalt tuffs, formed by explosive eruption of basalt through

2929-455: Is ultimately derived from Late Latin basaltes , a misspelling of Latin basanites "very hard stone", which was imported from Ancient Greek βασανίτης ( basanites ), from βάσανος ( basanos , " touchstone "). The modern petrological term basalt , describing a particular composition of lava -derived rock, became standard because of its use by Georgius Agricola in 1546, in his work De Natura Fossilium . Agricola applied

3030-526: The Aare . The Aare more than doubles the Rhine's water discharge, to an average of slightly more than 1,000 m /s (35,000 cu ft/s), and provides more than a fifth of the discharge at the Dutch border. The Aare also contains the waters from the 4,274 m (14,022 ft) summit of Finsteraarhorn , the highest point of the Rhine basin . Between Eglisau and Basel , the vast majority of its length,

3131-665: The Anterior Rhine and the Posterior Rhine join and form the Alpine Rhine. The river makes a distinctive turn to the north near Chur . This section is nearly 86 km long, and descends from a height of 599 meters to 396 meters. It flows through a wide glacial Alpine valley known as the Rhine Valley ( German : Rheintal ). Near Sargan a natural dam, only a few meters high, prevents it from flowing into

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3232-719: The Belgian coal measures . Rhine River The Rhine ( / r aɪ n / RYNE ) is one of the major European rivers . The river begins in the Swiss canton of Graubünden in the southeastern Swiss Alps . It forms the Swiss-Liechtenstein border and partly the Swiss-Austrian and Swiss-German borders. After that the Rhine defines much of the Franco-German border , after which it flows in

3333-539: The Clementine mission demonstrate that the lunar maria possess a continuum of titanium concentrations, and that the highest concentrations are the least abundant. Lunar basalts show exotic textures and mineralogy, particularly shock metamorphism , lack of the oxidation typical of terrestrial basalts, and a complete lack of hydration . Most of the Moon 's basalts erupted between about 3 and 3.5 billion years ago, but

3434-815: The Neckar in Mannheim and the Main across from Mainz. In Mainz, the Rhine leaves the Upper Rhine Valley and flows through the Mainz Basin. The southern half of the Upper Rhine forms the border between France ( Alsace ) and Germany (Baden-Württemberg). The northern part forms the border between the German states of Rhineland-Palatinate in the west on the one hand, and Baden-Württemberg and Hesse on

3535-457: The Obersee with the 30 cm lower Untersee . Distance markers along the Rhine measure the distance from the bridge in the old city center of Konstanz. For most of its length, the Seerhein forms the border between Germany and Switzerland. The exception is the old city center of Konstanz, on the Swiss side of the river. The Seerhein emerged in the last thousands of years, when erosion caused

3636-1228: The Paraná Traps in Brazil, the Siberian Traps in Russia , the Karoo flood basalt province in South Africa, and the Columbia River Plateau of Washington and Oregon . Basalt is also prevalent across extensive regions of the Eastern Galilee , Golan , and Bashan in Israel and Syria . Basalt also is common around volcanic arcs, specially those on thin crust . Ancient Precambrian basalts are usually only found in fold and thrust belts, and are often heavily metamorphosed. These are known as greenstone belts , because low-grade metamorphism of basalt produces chlorite , actinolite , epidote and other green minerals. As well as forming large parts of

3737-701: The Rhine knee , a major bend, where the overall direction of the Rhine changes from west to north. Here the High Rhine ends. Legally, the Central Bridge is the boundary between High and Upper Rhine. The river now flows north as Upper Rhine through the Upper Rhine Plain , which is about 300 km long and up to 40 km wide. The most important tributaries in this area are the Ill below of Strasbourg,

3838-400: The Rhine knee , the river turns north and leaves Switzerland altogether. The High Rhine is characterized by numerous dams. On the few remaining natural sections, there are still several rapids . Over its entire course from Lake Constance to the Swiss border at Basel the river descends from 395 m to 252 m. In the center of Basel, the first major city in the course of the stream, is

3939-701: The Saxothuringian Zone to the south, meaning its rocks have generally been at smaller depths and under lower temperatures. The Subvariscan Zone north of the Rhenohercynian Zone was untouched by Hercynian metamorphism. During the Hercynian orogeny, the Rhenohercynian zone was folded and thrust internally. It was thrust over the foreland to the north (the London-Brabant Massif and other Avalonian terranes ). From

4040-750: The canton of Ticino is drained by the Reno di Medel , which crosses the geomorphologic Alpine main ridge from the south. All streams in the source area are partially, sometimes completely, captured and sent to storage reservoirs for the local hydro-electric power plants. The culminating point of the Anterior Rhine's drainage basin is the Piz Russein of the Tödi massif of the Glarus Alps at 3,613 meters (11,854 ft) above sea level. It starts with

4141-680: The confluence of the Rein Anteriur/Vorderrhein and Rein Posteriur/Hinterrhein next to Reichenau in Tamins . Above this point is the extensive catchment area of the headwaters of the Rhine. This area belongs almost exclusively to the Swiss canton of Grisons ( Graubünden ), ranging from Saint-Gotthard Massif in the west via one valley lying in the canton of Ticino and Sondrio ( Lombardy , Italy) in

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4242-715: The folded sequences of Cornwall, the Ardennes , the Eifel and the Harz. From the Frasnian age (380 million years ago) the mafic volcanism ended, and the basin came locally under compressional stress , which led to folding and thrusting in the sedimentary rocks. Somewhere near the end of the Devonian, a subduction zone developed under the Mid-German/Normannian highs and Rhenohercynian crust began to subduct. This

4343-524: The hypabyssal and plutonic equivalents of basalt. During the Hadean , Archean , and early Proterozoic eons of Earth's history, the chemistry of erupted magmas was significantly different from what it is today, due to immature crustal and asthenosphere differentiation. The resulting ultramafic volcanic rocks, with silica (SiO 2 ) contents below 45% and high magnesium oxide (MgO) content, are usually classified as komatiites . The word "basalt"

4444-524: The lanthanide or rare-earth elements (REE) can be a useful diagnostic tool to help explain the history of mineral crystallisation as the melt cooled. In particular, the relative abundance of europium compared to the other REE is often markedly higher or lower, and called the europium anomaly . It arises because Eu can substitute for Ca in plagioclase feldspar, unlike any of the other lanthanides, which tend to only form cations . Mid-ocean ridge basalts (MORB) and their intrusive equivalents, gabbros, are

4545-516: The 19th century. While it was slightly modified during the Roman occupation, it was not until the emergence of engineers such as Johann Gottfried Tulla that significant modernization efforts changed the shape of the river. Earlier work under Frederick the Great surrounded efforts to ease shipping and construct dams to serve coal transportation. Tulla is considered to have domesticated the Upper Rhine,

4646-424: The Anterior Rhine and the Rhine as a whole. The Posterior Rhine rises in the Rheinwald below the Rheinwaldhorn . The source of the river is generally considered north of Lai da Tuma/Tomasee on Rein Anteriur/Vorderrhein , although its southern tributary Rein da Medel is actually longer before its confluence with the Anterior Rhine near Disentis . The Anterior Rhine arises from numerous source streams in

4747-401: The Austrian state of Vorarlberg , and the Swiss cantons of Thurgau and St. Gallen . The Rhine flows into it from the south following the Swiss-Austrian border. It is located at approximately 47°39′N 9°19′E  /  47.650°N 9.317°E  / 47.650; 9.317 . The flow of cold, grey mountain water continues for some distance into the lake. The cold water flows near

4848-402: The Earth's crust, basalt also occurs in other parts of the Solar System. Basalt commonly erupts on Io (the third largest moon of Jupiter ), and has also formed on the Moon , Mars , Venus , and the asteroid Vesta . The dark areas visible on Earth's moon , the lunar maria , are plains of flood basaltic lava flows. These rocks were sampled both by the crewed American Apollo program and

4949-420: The High Rhine forms the border between Germany and Switzerland . Only for brief distances at its extremities does the river run entirely within Switzerland; at the eastern end it separates the bulk of the canton of Schaffhausen and the German exclave of Büsingen am Hochrhein on the northern bank from cantons of Zürich and Thurgau , while at the western end it bisects the canton of Basel-Stadt . Here, at

5050-454: The Latin Ren- . The Gaulish name Rēnos ( Proto-Celtic or pre-Celtic *Reinos ) belongs to a class of river names built from the PIE root *rei- "to move, flow, run", also found in other names such as the Reno in Italy. The grammatical gender of the Celtic name (as well as of its Greek and Latin adaptation) is masculine, and the name remains masculine in German, Dutch, French, Spanish and Italian. The Old English river name

5151-410: The Ligerian cordillera. In the Siegenian/Pragian and Emsian the Rhenohercynic basin was a back-arc basin behind this cordillera. Tectonic subsidence in a system of horsts and grabens together with basaltic volcanism resulted in the creation of new oceanic lithosphere . In the Middle Devonian a second basin, the Saxothuringian / Armorican basin , developed south of the Rhenohercynian basin. To

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5252-471: The Posterior Rhine is joined by the Albula , from the east, from the Albula Pass region. The Albula draws its water mainly from the Landwasser with the Dischmabach as the largest source stream, but almost as much from the Gelgia , which comes down from the Julier Pass . Numerous larger and smaller tributary rivers bear the name of the Rhine or equivalent in various Romansh idioms, including Rein or Ragn , including: Next to Reichenau in Tamins

5353-453: The Rhine into Lake Constance forms an inland delta . The delta is delimited in the west by the Alter Rhein and in the east by the modern canalized section of the Alpine Rhine ( Fußacher Durchstich ). Most of the delta is a nature reserve and bird sanctuary . It includes the Austrian towns of Gaißau , Höchst and Fußach . The natural Rhine originally branched into at least two arms and formed small islands by precipitating sediments. In

5454-442: The area around the river was made more habitable for humans on flood plains as the rate of flooding decreased sharply. On the French side, the Grand Canal d'Alsace was dug, which carries a significant part of the river water, and all of the traffic. In some places, there are large compensation pools, for example, the huge Bassin de compensation de Plobsheim in Alsace. The Upper Rhine has undergone significant human change since

5555-429: The basalt/andesite field of the QAPF diagram. Basalt is further distinguished from andesite by its silica content of under 52%. It is often not practical to determine the mineral composition of volcanic rocks, due to their very small grain size, in which case geologists instead classify the rocks chemically, with particular emphasis on the total content of alkali metal oxides and silica ( TAS ); in that context, basalt

5656-404: The canalized Rhine into the lake. Its water has a darker color than the Rhine; the latter's lighter suspended load comes from higher up the mountains. It is expected that the continuous input of sediment into the lake will silt up the lake. This has already happened to the former Lake Tuggenersee . The cut-off Old Rhine at first formed a swamp landscape. Later an artificial ditch of about two km

5757-420: The centers Basel, Strasbourg and Mannheim-Ludwigshafen. Strasbourg is the seat of the European Parliament , and so one of the three European capitals is located on the Upper Rhine. The Upper Rhine region was changed significantly by a Rhine straightening program in the 19th century. The rate of flow was increased and the ground water level fell significantly. Dead branches were removed by construction workers and

5858-603: The changes proposed along the Rhine, one was "the Treaty for the Rectification of the Rhine flow from Neuberg to Dettenheim"(1817), which surrounded states such as Bourbon France and the Bavarian Palatinate . Loops, oxbows , branches and islands were removed along the Upper Rhine so that there would be uniformity to the river. The engineering of the Rhine was not without protest, farmers and fishermen had grave concerns about valuable fishing areas and farmland being lost. While some areas lost ground, other areas saw swamps and bogs be drained and turned into arable land. Johann Tulla had

5959-429: The characteristic igneous rocks formed at mid-ocean ridges. They are tholeiitic basalts particularly low in total alkalis and in incompatible trace elements, and they have relatively flat REE patterns normalized to mantle or chondrite values. In contrast, alkali basalts have normalized patterns highly enriched in the light REE, and with greater abundances of the REE and of other incompatible elements. Because MORB basalt

6060-418: The continental margin. It separated the London-Brabant Massif to the north from the Normannian and Mid-German Highs to the south. In the Middle Devonian (from 390 million years ago) a subduction zone existed south of Laurussia, where oceanic lithosphere of the Rheic Ocean subducted beneath the Mid-German/Normannian highs. Volcanism above the subduction zone created a cordillera -type mountain chain,

6161-403: The continents of Laurussia (north) and Gondwana (south) from the Silurian onwards. The southern margin of Laurussia was formed during the Caledonian orogeny of the Silurian period, about 420 million years ago . In the Gedinnian/Lochkovian (Early Devonian) the southern part of the Caledonian mountain belt became a region of north–south extension . An elongated basin was formed parallel to

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6262-477: The country alongside the industrial revolution. For the German state, making the river more predictable was to ensure development projects could easily commence. The section of the Upper Rhine downstream from Mainz is also known as the "Island Rhine". Here a number of river islands occur, locally known as "Rheinauen". Basalt Basalt ( UK : / ˈ b æ s ɔː l t , - əl t / ; US : / b ə ˈ s ɔː l t , ˈ b eɪ s ɔː l t / )

6363-415: The creek Aua da Russein (lit.: "Water of the Russein"). In its lower course, the Anterior Rhine flows through a gorge named Ruinaulta (Flims Rockslide). The whole stretch of the Anterior Rhine to the Alpine Rhine confluence next to Reichenau in Tamins is accompanied by a long-distance hiking trail called Senda Sursilvana . The Posterior Rhine flows first east-northeast, then north. It flows through

6464-447: The crust, forming an apron of mixed basalt and wall rock breccia and a fan of basalt tuff further out from the volcano. Amygdaloidal structure is common in relict vesicles and beautifully crystallized species of zeolites , quartz or calcite are frequently found. During the cooling of a thick lava flow, contractional joints or fractures form. If a flow cools relatively rapidly, significant contraction forces build up. While

6565-410: The destruction of the last oceanic crust of the basin. Its sedimentary fill was, however, not (totally) subducted but instead thrust northward. During the later part of the Carboniferous period ( Westphalian and Stephanian ) the Rhenohercynian zone formed the foreland of a relatively fast-developing Hercynian mountainbelt to the south. Isostatic subsidence of the foreland resulted in the development of

6666-414: The east the basin merges with the East-Silesian basin of southern Poland . The sedimentary rocks that were laid down in the basin are often weakly metamorphic ( greenschist facies ). Most geologists consider the South-Portuguese zone to be a continuation of the zone to the west. Whether the Rhenohercynian Basin was a continuous feature or rather a string of temporaneously interconnected smaller basins

6767-494: The evolution of the Earth's mantle . Isotopic ratios of noble gases , such as He / He, are also of great value: for instance, ratios for basalts range from 6 to 10 for mid-ocean ridge tholeiitic basalt (normalized to atmospheric values), but to 15–24 and more for ocean-island basalts thought to be derived from mantle plumes . Source rocks for the partial melts that produce basaltic magma probably include both peridotite and pyroxenite . The shape, structure and texture of

6868-444: The flow is diverted off the island of Mainau into Lake Überlingen. Most of the water flows via the Constance hopper into the Rheinrinne ("Rhine Gutter") and Seerhein. Depending on the water level, this flow of the Rhine water is clearly visible along the entire length of the lake. The Rhine carries very large amounts of debris into the lake – over three million cubic meters (110,000,000 cu ft) annually. In

6969-416: The goal of shortening and straightening the Upper Rhine. Early engineering projects the Upper Rhine also had issues, with Tulla's project at one part of the river creating rapids, after the Rhine cut down from erosion to sheer rock. Engineering along the Rhine eased flooding and made transportation along the river less cumbersome. These state projects were part of the advanced and technical progress going on in

7070-437: The islands of Hawaiʻi , the Faroe Islands , and Réunion . The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Basalt is the rock most typical of large igneous provinces . These include continental flood basalts , the most voluminous basalts found on land. Examples of continental flood basalts included the Deccan Traps in India , the Chilcotin Group in British Columbia , Canada ,

7171-418: The lake level to be lowered by about 10 meters. Previously, the two lakes formed a single lake, as the name still suggests. Like in the Obersee, the flow the Rhine can be traced in the Untersee. Here, too, the river water is hardly mixed with the lake water. The northern parts of the Untersee (Lake Zell and Gnadensee) remain virtually unaffected by the flow. The river traverses the southern, which, in isolation,

7272-482: The local Alemannic dialect, the singular is pronounced "Isel" and this is also the local pronunciation of Esel (" Donkey "). Many local fields have an official name containing this element. A regulation of the Rhine was called for, with an upper canal near Diepoldsau and a lower canal at Fußach, in order to counteract the constant flooding and strong sedimentation in the western Rhine Delta. The Dornbirner Ach had to be diverted, too, and it now flows parallel to

7373-604: The magma as it decompresses during its approach to the surface; the erupted lava then solidifies before the gases can escape. When vesicles make up a substantial fraction of the volume of the rock, the rock is described as scoria . The term basalt is at times applied to shallow intrusive rocks with a composition typical of basalt, but rocks of this composition with a phaneritic (coarser) groundmass are more properly referred to either as diabase (also called dolerite) or—when they are more coarse-grained (having crystals over 2 mm across)—as gabbro . Diabase and gabbro are thus

7474-416: The magma to the surface, embedded in a finer-grained matrix . These phenocrysts are usually made of augite, olivine , or a calcium-rich plagioclase, which have the highest melting temperatures of any of the minerals that can typically crystallize from the melt, and which are therefore the first to form solid crystals. Basalt often contains vesicles ; they are formed when dissolved gases bubble out of

7575-710: The mantle. Many alkali basalts may be formed at greater depths, perhaps as deep as 150–200 km. The origin of high-alumina basalt continues to be controversial, with disagreement over whether it is a primary melt or derived from other basalt types by fractionation. Relative to most common igneous rocks, basalt compositions are rich in MgO and CaO and low in SiO 2 and the alkali oxides, i.e., Na 2 O + K 2 O , consistent with their TAS classification . Basalt contains more silica than picrobasalt and most basanites and tephrites but less than basaltic andesite . Basalt has

7676-457: The most voluminous of all volcanic formations. Basaltic magmas within Earth are thought to originate from the upper mantle . The chemistry of basalts thus provides clues to processes deep in Earth's interior . Basalt is composed mostly of oxides of silicon, iron, magnesium, potassium, aluminum, titanium, and calcium. Geologists classify igneous rock by its mineral content whenever possible;

7777-499: The mouth region, it is therefore necessary to permanently remove gravel by dredging. The large sediment loads are partly due to the extensive land improvements upstream. Three countries border the Obersee, namely Switzerland in the south, Austria in the southeast and the German states of Bavaria in the northeast and Baden-Württemberg in the north and northwest. The Seerhein is only 4 kilometers (2.5 mi) long. It connects

7878-683: The north bank and Switzerland on the south, except both sides are Swiss in Stein am Rhein , where the High Rhine flows out of the lake. The High Rhine ( Hochrhein ) begins in Stein am Rhein at the western end of the Untersee. Now flowing generally westwards, it passes over the Rhine Falls ( Rheinfall ) below Schaffhausen before being joined – near Koblenz in the canton of Aargau  – by its major tributary,

7979-410: The oldest samples are 4.2 billion years old, and the youngest flows, based on the age dating method of crater counting , are estimated to have erupted only 1.2 billion years ago. From 1972 to 1985, five Venera and two VEGA landers successfully reached the surface of Venus and carried out geochemical measurements using X-ray fluorescence and gamma-ray analysis. These returned results consistent with

8080-506: The open Sztal valley and then through Lake Walen and Lake Zurich into the Aare . The Alpine Rhine begins in the westernmost part of the Swiss canton of Graubünden , and later forms the border between Switzerland to the west and Liechtenstein and later Austria to the east. As an effect of human work, it empties into Lake Constance on Austrian territory and not on the border that follows its old natural river bed called Alter Rhein ( lit.   ' Old Rhine ' ). The mouth of

8181-547: The other hand, in the east and north. A curiosity of this border line is that the parts of the city of Mainz on the right bank of the Rhine were given to Hesse by the occupying forces in 1945. The Upper Rhine was a significant cultural landscape in Central Europe already in antiquity and during the Middle Ages . Today, the Upper Rhine area hosts many important manufacturing and service industries, particularly in

8282-475: The rate of cooling; very rapid cooling may result in very small (<1 cm diameter) columns, while slow cooling is more likely to produce large columns. The character of submarine basalt eruptions is largely determined by depth of water, since increased pressure restricts the release of volatile gases and results in effusive eruptions. It has been estimated that at depths greater than 500 metres (1,600 ft), explosive activity associated with basaltic magma

8383-411: The relative volume percentages of quartz (crystalline silica (SiO 2 )), alkali feldspar , plagioclase , and feldspathoid ( QAPF ) are particularly important. An aphanitic (fine-grained) igneous rock is classified as basalt when its QAPF fraction is composed of less than 10% feldspathoid and less than 20% quartz, and plagioclase makes up at least 65% of its feldspar content. This places basalt in

8484-523: The river. Some adjacent towns are named after it, such as Rheinau , Rheineck , Rheinfelden (CH) and Rheinfelden (D). The International Commission for the Hydrology of the Rhine Basin (CHR) and EUWID contend that the river could experience a massive decrease in volume, or even dry up completely in case of drought, within the next 30 to 80 years, as a result of the climate crisis . The Rhine

8585-595: The robotic Russian Luna program , and are represented among the lunar meteorites . Lunar basalts differ from their Earth counterparts principally in their high iron contents, which typically range from about 17 to 22 wt% FeO. They also possess a wide range of titanium concentrations (present in the mineral ilmenite ), ranging from less than 1 wt% TiO 2 , to about 13 wt.%. Traditionally, lunar basalts have been classified according to their titanium content, with classes being named high-Ti, low-Ti, and very-low-Ti. Nevertheless, global geochemical maps of titanium obtained from

8686-403: The rock at the landing sites being basalts, including both tholeiitic and highly alkaline basalts. The landers are thought to have landed on plains whose radar signature is that of basaltic lava flows. These constitute about 80% of the surface of Venus. Some locations show high reflectivity consistent with unweathered basalt, indicating basaltic volcanism within the last 2.5 million years. Basalt

8787-462: The sea it usually forms pillow basalts. However, when ʻaʻā enters the ocean it forms a littoral cone , a small cone-shaped accumulation of tuffaceous debris formed when the blocky ʻaʻā lava enters the water and explodes from built-up steam. The island of Surtsey in the Atlantic Ocean is a basalt volcano which breached the ocean surface in 1963. The initial phase of Surtsey's eruption

8888-769: The south it was overthrust by the Mid-German Crystalline High , part of the Saxothuringian Zone. The metamorphic grade or degree of metamorphism increases towards the south or southeast. The southern edge of the Rhenish Massif lies in the Northern Phyllite Zone , which has a higher grade than other parts of the zone. The Rhenohercynian basin was situated north of the Rheic Ocean , the ocean that spread between

8989-673: The south to the Flüela Pass in the east. The Rhine is one of four major rivers taking their source in the Gotthard region, along with the Ticino (drainage basin of the Po ), Rhône and Reuss (Rhine basin). The Witenwasserenstock is the triple watershed between the Rhine, Rhône and Po. Traditionally, Lake Toma near the Oberalp Pass in the Gotthard region is seen as the source of

9090-412: The surface and at first does not mix with the warmer, green waters of Upper Lake. But then, at the so-called Rheinbrech , the Rhine water abruptly falls into the depths because of the greater density of cold water. The flow reappears on the surface at the northern (German) shore of the lake, off the island of Lindau . The water then follows the northern shore until Hagnau am Bodensee . A small fraction of

9191-670: The term "basalt" to the volcanic black rock beneath the Bishop of Meissen's Stolpen castle , believing it to be the same as the "basaniten" described by Pliny the Elder in AD ;77 in Naturalis Historiae . On Earth, most basalt is formed by decompression melting of the mantle . The high pressure in the upper mantle (due to the weight of the overlying rock ) raises the melting point of mantle rock, so that almost all of

9292-619: The three valleys named Rheinwald , Schams and Domleschg - Heinzenberg . The valleys are separated by the Rofla Gorge and Viamala Gorge. Its sources are located in the Adula Alps ( Rheinwaldhorn , Rheinquellhorn , and Güferhorn ). The Avers Rhine joins from the south. One of its headwaters, the Reno di Lei (stowed in the Lago di Lei ), is partially located in Italy. Near Sils

9393-410: The total thickness of the sediments can in some places be more than several kilometers. When a foreland basin was formed in the Rhenohercynian zone, this was filled with upper Carboniferous ( Pennsylvanian ) flysch and molasse sediments. The Namurian is characterized by flysch, in the Westphalian this gradually grades into molasse and other continental deposits, among which the thick coal layers of

9494-499: The upper Surselva and flows in an easterly direction. One source is Lai da Tuma (2,345 m (7,694 ft)) with the Rein da Tuma , which is usually indicated as source of the Rhine, flowing through it. Into it flow tributaries from the south, some longer, some equal in length, such as the Rein da Medel , the Rein da Maighels , and the Rein da Curnera . The Cadlimo Valley in

9595-580: The upper mantle is solid. However, mantle rock is ductile (the solid rock slowly deforms under high stress). When tectonic forces cause hot mantle rock to creep upwards, pressure on the ascending rock decreases, and this can lower its melting point enough for the rock to partially melt , producing basaltic magma. Decompression melting can occur in a variety of tectonic settings, including in continental rift zones, at mid-ocean ridges , above geological hotspots , and in back-arc basins . Basalt also forms in subduction zones , where mantle rock rises into

9696-727: The west some crustal convergence took place, and the Normannian High was partly thrust over the sedimentary basin fill of the Rhenohercynian basin. The Rhenohercynian basin disappeared when the continent Gondwana collided with Laurussia in the course of the Carboniferous period (the Hercynian orogeny ). The sedimentary rocks in the basin were thrust in a series of piggyback basins over the northern foreland (the London-Brabant Massif). These rocks now form

9797-1038: Was adapted in Roman-era geography (1st century BC) as Latin Rhenus , and as Greek Ῥῆνος ( Rhēnos ). The spelling with Rh- in English Rhine as well as in German Rhein and French Rhin is due to the influence of Greek orthography, while the vocalization -i- is due to the Proto-Germanic adoption of the Gaulish name as * Rīnaz , via Old Frankish giving Old English Rín , Old High German Rīn , early Middle Dutch ( c.  1200 ) Rijn (then also spelled Ryn or Rin ). The modern German diphthong Rhein (also used in Romansh ) Rein, Rain

9898-468: Was dug. It was made navigable to the Swiss town of Rheineck . Lake Constance consists of three bodies of water: the Obersee ("upper lake"), the Untersee ("lower lake"), and a connecting stretch of the Rhine, called the Seerhein ("Lake Rhine"). The lake is situated in Germany, Switzerland and Austria near the Alps. Specifically, its shorelines lie in the German states of Bavaria and Baden-Württemberg ,

9999-400: Was highly explosive, as the magma was quite fluid, causing the rock to be blown apart by the boiling steam to form a tuff and cinder cone. This has subsequently moved to a typical pāhoehoe-type behaviour. Volcanic glass may be present, particularly as rinds on rapidly chilled surfaces of lava flows, and is commonly (but not exclusively) associated with underwater eruptions. Pillow basalt

10100-705: Was the short Bretonnic phase of the Hercynian orogeny. It was followed, from the Tournaisian (early Carboniferous, 355 million years ago) till the end of the Visean by a new period of extension. During the Sudetic (main) phase of the Hercynian orogeny (330-320 million years ago, Late-Visean and Namurian / Serpukhovian ) compressional tectonics had the upper hand again. In the Namurian age full-scale continental collision between Laurussia and Gondwana resulted in

10201-465: Was variously inflected as masculine or feminine; and its Old Icelandic adoption was inflected as feminine. The length of the Rhine is conventionally measured in "Rhine-kilometers" ( Rheinkilometer ), a scale introduced in 1939 which runs from the 0 km datum at Old Rhine Bridge in the city of Konstanz , at the western end of Lake Constance , to the Hook of Holland at 1,036.20 km. The river

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