Metamorphism is the process of mineralogical and structural (textural) changes of rocks in the solid state in response to physical and/or chemical conditions that differ from those under which they originated. Physical condition changes include temperature and pressure. Chemical conditions may include water and/or carbon dioxide pore (openings between crystals) solutions with dissolved solids. A metamorphic fabric is the geometric arrangement of structures within a rock in response to metamorphic processes. Foliation is a planar rock fabric. It is where the minerals or other components of a rock align themselves in parallel planes. This can occur when the rock is first formed or afterward by the rock being subjected to heat and/or pressure during deformational tectonic events. The typical rock sequence of slate, phyllite, schist and gneiss is an example of foliation caused by metamorphism.