Basalt

Basalt is a basic (SiO2 - poor ) volcanic rock. It consists mainly of a mixture of iron and magnesium silicates with pyroxene and calcium- rich feldspar ( plagioclase ) and usually also with olivine. Basalt is the volcanic equivalent of the gabbro ( plutonic ), which has the same chemical composition.

The controversy over the origin of the basalts in the late 18th century called over the origin of the earth, even basalt dispute, is in its humanities meaning almost synonymous with the controversy over heliocentrism image.

Word origin

The word basalt is narrated by Pliny and was used by Georgius Agricola in his work De Natura 1546 Fossilium again, but as a " fossil". Abraham Gottlob Werner uses this term in 1787 as a rock name in his description of the various kinds of rock, without making so that a precise definition about its mineral composition. Louis Cordier 1816 restricts the name to a composition of augite and labradorite with varying proportions of olivine one. Karl Heinrich Rose Bush in 1887 formulated a new definition.

The Etymological dictionary of the German language noted, the basalt was since the 18th century in the German detectable and was borrowed from the Latin basalt, which, in turn, a prescription of the Greek βασανίτης [ λίθος ] ( touchstone, very hard stone ), basanítēs [ líthos ], " touchstone " or βάσανος, BASANOS, " burin - stone " is. The word has its origin possibly in the Egyptian. The Petro graph Franz Loewinson - Lessing argues that basalt " one of the oldest petrographic descriptions is " and comes from the Ethiopian. Thus bselt or bsalt to denote cooked state. He also announced that, according to Pliny the Elder, the first used basalts from Ethiopia arrived.

As diabase and melaphyre geologically old basalts are known, which have also undergone a slight change in their structure and their mineral composition by metamorphism.

Formation

Basalt formed during the melting of the mantle, low-viscosity, low- SiO2 magma cools at the surface or in the ocean at the exit relatively quickly basalt. The magmas have when they leave usually temperatures between 900 ° C and 1200 ° C depending on their chemistry. The magma is usually not liquid at 100%, there often are also inclusions ( Xenocryst ) of minerals or whole rocks ( Xenolith ) with a higher melting point therein that are entrained during ascent.

Basalt is, considering both the continents and the bottom of the sea, the rock with the largest circulation. Of these, in turn, form, named after the village in the Saarland tholeiitic basalts Tholey the main part of the oceanic crust and of several occurrences of the continental crust.

Almost all deep ocean floors are made of basalt, which is there only covered by a more or less powerful ceiling younger sediments. Along the global mid-ocean ridge lava ascends and produced by the growing cold molten rock new ocean floor between tectonic plates apart soft. There are also other development areas for marine basalt. Depending on the point of origin is referred to as the basalt

• MORB (mid ocean ridge basalt at spreading zones between two oceanic plates ),
• CMB ( continental margin basalt, at subduction zones between oceanic and continental plate ),
• IAB ( Iceland arc basalt, at subduction zones between two oceanic plates ) or
• OIB (ocean Iceland basalt, at hot spots within a plate ).

The basalt types differ because of the different development processes in chemical composition.

Basalt is also widespread on the mainland before and is usually in tectonic zones of weakness such as grave breaches or occurring on the mainland Hot Spots bound. The rule is: a lot of basalt - rhyolite little.

Appearance

Basalt is dark gray to black usually. It consists largely of a fine-grained groundmass. Larger, with the naked eye to be recognized phenocrysts are relatively rare, but may occur more frequently in some Basaltvarietäten.

The appearance of basaltic lava cooled off is mainly dependent on two factors. Erupted lava cools very quickly into a cohesive rock fabric, which solidifies depending on temperature and gas content than pahoehoe lava or as Aa lava. Find the cooling but delayed instead, caused by the contraction often meter-long rectangular basalt columns ( columnar basalt ) that form perpendicular to the cooling surface, preferably with a hexagonal ( six-sided ) geometry. A rather infrequent manifestation of basalt basalt is the ball that it is preferable to place at the edges of basalt deposits.

Composition

All basalts have a basic composition, that is, they are low in SiO2. Predominant groups of minerals are plagioclase (usually labradorite ) and pyroxene, mainly as augite. Olivine and Foide occur in some basalt deposits; but they may also be missing. Also biotite and hornblende may occur. Alkali feldspar and quartz or only subordinate basalts come in before, however.

Alkaline basalts are characterized by the presence of normative nepheline and a higher content of alkalis (Na ) relative to Si and Al from subalkalische basalts, however, do not have normative nepheline, but may be expelled for normative quartz. The total content of potassium oxide ( K2O) and sodium oxide ( Na2O) is higher in alkaline basalts.

Overall, basalts prove by their chemical composition, as extremely variable rocks, which is in contradiction to their very uniform appearance. Depending on the origin zone ( see the following section ), the mineral composition vary greatly. One therefore distinguishes several subtypes according to their chemical composition:

• Tholeiitbasalt - plagioclase, augite and ( ortho ) pyroxene predominate. This group is named after the place Tholey Saarland, and these rocks are mainly in the Saar-Nahe region and near Bolzano and on ocean islands, not least in Hawaii before.
• Alkali basalt and Alkaliolivinbasalt - with olivine and clear Nephelingehalt. Alkali basalts occur in the Eifel, Rhön, the Lausitz / Silesia, northern Bohemia and in the Massif Central in France, especially in Central Europe.
• Olivinbasalt - with a clear Olivingehalt, no orthopyroxene.
• Feldspatbasalt - with feldspar phenocrysts as.
• As basanites is called with the basalt closely related rocks with very large levels of Foiden and olivine. They are therefore in a different field of Streckeisen diagram.

The following summary gives an indication of the chemical composition:

• 50% SiO2
• Al2O3 by 20 %
• FeO, CaO and MgO at 10 %
• K2O and Na2O by 5%
• TiO2 and sulfur compounds in small quantities.

Basalt on other celestial bodies

Basalt is also a common rock on all the terrestrial planets (Mercury, Venus, Mars) and the moon. Many meteorites have the same chemical composition as basalt. With their help one can draw conclusions about the formation of our solar system.

Use

Basalts are used for concrete structures, floor and stair coverings, cladding panels, and grave monuments and in the stone sculpture. In addition, basalt is used as a building material due to its pressure-and wear-resistant, difficult to work, but not too brittle character mainly for the substructure of roads and railway tracks use. Until the year 1950/1960 it was processed as a mosaic, small and large patch in the Path and road construction. To date, it is often used repeatedly in the garden and landscaping as a patch ( new / used ), the surface is due to abrasion but smooth and slippery when wet. One example is called the blue or hard basaltic ( lava - Foidit ).

In the vicinity of volcanoes also houses basaltic rocks are built, what the villages is a dark character, such as towns in the Eifel ( Mendig ) and Mount Etna in Sicily. Basaltbauten are very typical of the Hauran in southern Syria, which were built in the Bronze Age and because of the durability of the material often several centuries, in part, to this day, inhabited.

For centuries, basalt crosses are erected at waypoints. Many historically significant basalt crosses are mainly located in the room Mayen in the Eifel.

In the area of the eastern Bohemian Uplands ( České Středohoří ) and up to the Zittau mountains scattered buildings in villages and small towns present whose base masonry is composed of superimposed basalt columns of approximately equal length. The column heads thus form the outside of the base, if it is unrendered. In some rural settlements are also a few garden walls have received in this construction. It is worth noting that it is possible basalt columns split across only under very high effort.

A special form is represented by the so-called sun burner basalt, which breaks easily and is therefore unsuitable for many applications. The cause of the decay lies in its high content of analcime, which very easily weathered.

• Basalt as a cultural

Masonry: Paradise ( antechurch ) was founded in the Romanesque monastery Arnsburg with early Gothic windows forms

Basalt cross in the Eifel from 1751

Joseph Beuys planted 7000 oak trees, each with an accompanying basalt stone in Kassel.

The basalt dispute

The " basalt dispute" in the late 18th century was a debate about beliefs, worldviews and explaining the world. You should be evaluated as an important step in the processes that have led to our incurred " modern " world and the "modern" society. The basalt dispute was ostensibly a scientifically guided discussion, but arose from a theological question. On the side of the " Neptunists " Abraham Gottlob Werner leader, the discussion was long colored by the creation accounts of the Bible. Starting from the hullabaloo, Moses 1:1-2: In the beginning God created the heavens and the earth. And the earth was without form and void, and darkness was upon the deep; and the Spirit of God hovering over the waters. the formation of basalt from the primeval ocean was derived. The " Plutonists " leader James Hutton, put more aware of the biblical account now and could prevail eventually. Hutton's view of the world was by no means atheistic, but deistic - God had thus established the world according to his plan, but grabbed it no longer directly a. Johann Wolfgang Goethe theme of a dispute in different plants and one of the detained Eckermann discussions, and 1827 in the United States dedicated poem.

The United States America, you 're better off As our continent, the old, Did not ruined castles And no basalts. You will not interfere in the interior, For more alive time useless Remember And futile dispute. ...

Types of natural stone

• Londorfer basalt Hesse, Londorf
• Mayener basalt, a leucite tephrite ( Rhineland -Palatinate, GER)
• Basaltite, a leucite tephrite (Italy, Bolsena )

Amounts of basalt

Central Europe

• Baden-Wurttemberg Swabian Alb, in the area of the Swabian Volcano
• Hegau
• Odenwald, Katzenbuckel ( there is Basanit to )

• Gangolf mountain
• Kemnather basin
• Northern Stone Forest
• Imperial forest ( Fichtelgebirge)
• Park stone
• Rhön

• Vogelsberg; the largest contiguous basalt massif in Central Europe
• Hoher Meißner
• Nüsttal in the front Rhön
• Stoppelberg

• High Hagen Südniedersachsen
• Mountains Bramburg, Grefe castle and Backsberg to Adelebsen

• Desenberg, Warburger Borde

• Scheibenbergstraße ( Westerzgebirge )
• Baerenstein ( Westerzgebirge )
• Hirtstein ( Westerzgebirge )
• Pöhlberg ( Westerzgebirge )
• Geisingberg ( Erzgebirge )
• Wilisch (mountain ) ( Erzgebirge )
• Cottaer Spitzberg ( Erzgebirge )
• Castle Hill of Stolpen on the Elbe Sandstone Mountains
• Space mountain in the Elbe Sandstone Mountains
• Lusatian mountains Landeskrone
• Löbauer mountain
• Kottmar

• Gleichberge

• Druidenstein (border Winner Country / Westerwald)
• Area around Bad Marienberg (Westerwald ) with the Basalt Park and the Stöffel Park
• Unkelstein

• Styria ( market town Klöch )

• Prekmurje ( Goricko )

• Bohemian Highlands ( České Středohoří )
• Lusatian Mountains ( Luzicke hory)
• Doupov Mountains ( Doupovske hory)
• Nature reserve Ryžovna

• Celldömölk

• Bucium

Outside of Central Europe

• Giant's Causeway, Northern Ireland
• Staffa, Scotland

• France Ardèche, Cascade du Ray -Pic
• Massif Central

Basalt: Mansion rocks ( Panska scale) at Šenov / Steinschönau, Lusatian Mountains in the Czech Republic

Basalt columns on the park stone in Northeast Bavaria

Los Organos: Basalt columns on La Gomera, Canary Islands, Spain

Basalt columns in Namibia