Metamorphic Rock
Texture of Metamorphic Rock
Foliation in geology or rock refers to repetitive layering
in metamorphic rocks. Each layer may be as thin as a sheet of
paper, or over a meter in. It is caused by shearing forces (pressures
pushing different sections of the rock in different directions),
or differential pressure (higher pressure from one direction than in
others). The layers form parallel to the direction of the shear, or
perpendicular to the direction of higher pressure.
Nonfoliated metamorphic rocks are typically formed in
the absence of significant differential pressure or shear.