Geologically young andesite volcano are aligned along circum- Pacific and Mediterranean belts 3. Existence of Hawaii - land for habitation. This variation accounts for the differences in appearances in the rocks. Mafic Rocks - usually dark in color. Basalt is the most common mafic rock.
Name comes from feldspar.
Rhyolite is the most abundant vol. The chemical composition of the magna determines which minerals and how much of each will settle to form Igneous Rocks. This is based on their composition and texture. Composition Silica amount determines viscosity, violence of eruptions and also the particular rock that is formed. Using the minerals, one can identify the rocks but usually most extrusive rocks are fine grained and use of microscope would be useful.