Trachyandesite

A cut block of trachyandesite lava from a volcano in Auvergne, France, used as building stone, forming part of the wall of Clermont-Ferrand cathedral, France.

Trachyandesite is an extrusive igneous rock. It has little or no free quartz, but is dominated by alkali feldspar and sodic plagioclase along with one or more of the following mafic minerals: amphibole, biotite or pyroxene. Small amounts of nepheline may be present and apatite is a common accessory mineral.

Trachyandesitic magma can produce explosive Plinian eruptions, such as happened at Tambora in 1815.

Volcanoes Volcano types Caldera Cinder cone Complex volcano Cryovolcano Fissure vent Lava cone Lava dome Maar Mud volcano Parasitic cone Pyroclastic cone Pyroclastic shield Rootless cone Shield volcano Somma volcano Stratovolcano Subglacial volcano Submarine volcano Supervolcano Volcanic cone Volcanic field Volcanic rocks Volcanic rock Agglomerate Andesite Basalt Basaltic andesite Benmoreite Blairmorite Dacite Felsite Komatiite Latite Nephelinite Obsidian Phonolite Rhyodacite Rhyolite Trachyte Trachyandesite Trachybasalt Tuff List and volcanoes groups Lists of volcanoes Decade Volcanoes Volcanic belt Category Portal Commons WikiProject