Basaltic magmas intruded into this anomalously hot zone will prompt partial melting of the crust, and may mix with these melts to produce intermediate compositions, typically andesite to trachyte in composition.
Andesites are characteristic of subduction tectonic environments in active oceanic margins, such as the west coast of South America.
Classification of andesites may be refined according to the most abundant phenocryst.
Andesites are generally found as surface deposits and may therefore be considered the "extrusive" equivalent to diorite, which is formed beneath the Earth's surface (and is thus an "intrusive" or plutonic rock).
The term andesite is derived from the Andes mountain range, where specific types of lava were given this name.
The study of andesite has helped scientists understand the geological processes by which this igneous rock can be formed.
The resultant composition of andesite and intermediate magmas is based on fractional crystallisation, assimilation, partial melting, and contaminaton by the subducted slab.
Andesite is a type of igneous rock that is found in most volcanic regions of the world, especially around volcanoes that line the Pacific Basin.