What are some properties of basalt



  basalt is a basic (low-silica) effluent rock. It mainly consists of a mixture of iron and magnesium silicates with olivine and pyroxene as well as calcium-rich feldspar (plagioclase). Basalt is the volcanic equivalent of gabbro (plutonite), which has the same chemical composition.

Word origin

The word basalt has been traceable in German since the 18th century[1] and was derived from the lat. basaltēs borrowed, which in turn is a prescription of the Greek βασανίτης [λίθος], basanítēs [líthos], "Touchstone" or βάσανος, básanos, "Gravestone Stone" is; originally the word may come from[1] from Egyptian.

Geologically old basalts are referred to as diabase and melaphyr, which have also undergone a slight change in their structure and mineral composition through metamorphosis.

Emergence

Basalt is formed when thin, low-silica magma emerges from the surface of the earth and cools down relatively quickly to form basalt lava.

Look

Basalt is usually dark gray to black. For the most part, it consists of a fine-grained matrix. Larger insects that can be seen with the naked eye are relatively rare, but can be more common in some basalt varieties.

The appearance of cooled basaltic lava depends mainly on two factors. Erupted lava cools down very quickly to form a coherent rock structure that solidifies as pahoehoe lava or Aa lava, depending on the temperature and gas content. However, if the cooling takes place with a delay, the contraction often results in polygonal meter-long basalt columns that are perpendicular to the cooling surface. Here, hexagonal columns are preferably formed.

composition

All basalts have a basic composition, which means that they are poor in SiO2. The predominant mineral groups are plagioclase (mostly labradorite) and pyroxene, mostly as augite. Olivine and Foide occur in some basalt deposits; but they can also be absent. Biotite and hornblende can also occur. Alkali feldspar and quartz, on the other hand, do not occur in basalts or only to a minor extent.

Overall, basalts turn out to be extremely variable rocks in terms of their chemical composition, which contradicts their fairly uniform appearance. The mineral composition can vary greatly depending on the zone of origin (see section below). A distinction is therefore made between several sub-types according to their chemical composition:

  • Tholeiite basalt - plagioclase, augite and (ortho) pyroxene predominate
  • Olivine basalt - with a clear olivine content, no orthopyroxene
  • Alkali basalt and alkali olivin basalt - with olivine and significant nepheline content
  • as Basanites Basalt is used to denote rocks that are closely related and have very high contents of foids and olivine. They are therefore in a different field of the route iron diagram.

Zones of origin

Basalt is the most widely distributed rock, both on the continent and at the bottom of the ocean. Almost all deep ocean floors consist of basalt, which there is only covered by a more or less thick blanket of younger sediments. The lava rises along the global mid-ocean ridge and, as the rock melts, creates a new ocean floor between diverging tectonic plates. But there are also other areas where marine basalt is produced. Depending on the place of origin, the basalt is called

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

The basalt types differ in their chemical composition due to the different formation processes.

Basalt is also widespread on the mainland and is mostly tied to tectonic weak zones such as rift breaks or hot spots that occur on the mainland. The rule is: a lot of basalt - little rhyolite.

Basalt on other celestial bodies

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

Basalt as a building material

As a building material, basalt is mainly used for the substructure of roads and railroad tracks due to its pressure-resistant, difficult to work, but not too brittle character. Until 1950/1960 it was used as a mosaic, small and large pavement in path and road construction. To this day it is used again and again as a plaster (new / used) in gardening and landscaping. An example is the blue or hard basalt (foidite lava). Houses made of basaltic rock are also being built near volcanoes, which gives the villages a dark character. B. Localities in the Eifel (Mendig) and around Mount Etna in Sicily.

The so-called sunburner basalt is a special form, which disintegrates easily and is therefore unsuitable for many technical applications. The cause of the decay lies in its high content of analcime, which is extremely susceptible to weathering.

Types of natural stone

  • Basalt lava (Rhineland-Palatinate, Mayen)
  • Basaltite (Italy, Bolsena)

Occurrence of basalt

 

Central Europe

  • Baden-Wuerttemberg
    • Swabian Alb, in the area of ​​the Swabian volcano
    • Hegau
  • Bavaria
    • Gangolfsberg
    • Kemnather valley basin
    • Northern stone forest
    • Park stone
    • Rhön
    • Stoppelsberg
  • Hesse
    • Vogelsberg; the largest contiguous basalt massif in Central Europe
    • High Meissner
    • Odenwald, Katzenbuckel (there is basanite)
  • Lower Saxony
    • Hoher Hagen South Lower Saxony
  • Saxony
    • Scheibenberg (Western Ore Mountains)
    • Bärenstein (Western Ore Mountains)
    • Pöhlberg (Western Ore Mountains)
    • Geisingberg (Eastern Ore Mountains)
    • Wilisch (mountain) (Eastern Ore Mountains)
    • Castle hill of Stolpen on the Elbe Sandstone Mountains
    • Lusatian highlands
      • National crown
      • Löbauer Mountain
      • Kottmar
  • Westerwald
    • Area around Bad Marienberg (Westerwald) with the Basalt Park and the Stöffel Park
  • Vulkaneifel
  • Siebengebirge
  • France
    • Department Ardèche_ (Department), Cascade du Ray-Pic
  • Czech Republic
    • Central Bohemian Uplands (České středohoří)
    • Lusatian Mountains (Luzicke hory)
    • Duppau Mountains (Doupovske hory)
    • Ryžovna nature reserve
  • Hungary

outside of Central Europe

  • Giant's Causeway, Northern Ireland
  • Isle of Staffa, Scotland
  • Massif Central in France
  • La Gomera, Canary Islands, Spain
  • Faroe Islands
  • Iceland
  • Armenia
  • Vietnam
  • Cameroon and other African countries
  • Columbia Gorge (Washington / Oregon, USA)

See also

List of rocks, zeolite group

swell

  1. ab Kluge Etymological Dictionary of the German Language, 24th edition

Vulkanpark, basalt in the Eifel

Mayen basalt quarry, historical mining with cranes

Basalt quarry in Italy near Bolsena

Category: Vulcanite