Trachyandesite

A cut block of trachyandesite lava from a volcano in Auvergne, France, used as building stone, forming part of the walls of Clermont-Ferrand Cathedral, France
Trachyandesite is field S3 in the TAS diagram

Trachyandesite is an extrusive igneous rock with a composition between trachyte and andesite. It has little or no free quartz, but is dominated by sodic plagioclase and alkali feldspar. It is formed from the cooling of lava enriched in alkali metals and with an intermediate content of silica.[1][2]

The term trachyandesite had begun to fall into disfavor by 1985[1] but was revived to describe extrusive igneous rocks falling into the S3 field of the TAS classification. These are divided into sodium-rich benmoreite and potassium-rich latite.[3]

Trachyandesitic magma can produce explosive Plinian eruptions, such as happened at Tambora in 1815.[4] The Eyjafjallajökull 2010 eruption (VEI-4[5]), which disrupted European and transatlantic air travel from 15-20 April 2010,[6] for some time was dominated by trachyandesite.[7]

  1. ^ a b McBirney, Alexander R. (1984). Igneous petrology. San Francisco, Calif.: Freeman, Cooper. p. 503. ISBN 0198578105.
  2. ^ Neuendorf, Klaus K.E.; Mehl, James P. Jr.; Jackson, Julia A. (2011). Glossary of geology (Fifth revised ed.). American Geological Institute. ISBN 9781680151787.
  3. ^ Le Bas, M. J.; Streckeisen, A. L. (September 1991). "The IUGS systematics of igneous rocks". Journal of the Geological Society. 148 (5): 825–833. Bibcode:1991JGSoc.148..825L. doi:10.1144/gsjgs.148.5.0825. S2CID 28548230.
  4. ^ Self, S.; Gertisser, R.; Thordarson, T.; Rampino, M. R.; Wolff, J. A. (2004). "Magma volume, volatile emissions, and stratospheric aerosols from the 1815 eruption of Tambora" (PDF). Geophysical Research Letters. 31 (20): L20608. Bibcode:2004GeoRL..3120608S. doi:10.1029/2004GL020925. hdl:20.500.11820/6925218f-d09e-4f9d-9f2e-3ab8419b223f. S2CID 56290102.
  5. ^ Eyjafjallajokull. Eruptive history. Global Volcanism Program. Retrieved 26 August 2020.
  6. ^ Woodhouse, M. J.; Hogg, A. J.; Phillips, J. C.; Sparks, R. S. J. (January 2013). "Interaction between volcanic plumes and wind during the 2010 Eyjafjallajökull eruption, Iceland: VOLCANIC PLUMES AND WIND" (PDF). Journal of Geophysical Research: Solid Earth. 118 (1): 92–109. doi:10.1029/2012JB009592.
  7. ^ Donovan, Amy R; Oppenheimer, Clive (March 2011). "The 2010 Eyjafjallajökull eruption and the reconstruction of geography: Commentary". The Geographical Journal. 177 (1): 4–11. doi:10.1111/j.1475-4959.2010.00379.x.