Andesite is an aphanitic (fine-grained) to porphyritic (coarse-grained) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 20% quartz and 10% feldspathoid by volume, wit… See more

Andesite lava typically has a viscosity of 3.5 × 10 cP (3.5 × 10 Pa⋅s) at 1,200 °C (2,190 °F). This is slightly greater than the viscosity of smooth peanut butter. As a result, andesitic volcanism is often explosive, f… See more

Though andesite is common in other tectonic settings, it is particularly characteristic of convergent plate margins. Even before the Plate Tectonics Revolution, geologists had defined an andesite line in the wester… See more

Intermediate volcanic rocks are created via several processes:
1. Fractional crystallization of a mafic parent magma.
2. Partial melting of crustal material.
3. Magma mixing between felsic rhyolitic and mafic … See more