When Are Foliated Rocks Formed?

Extreme pressure may also lead to the formation of foliation, or flat layers in rocks that form as the rocks are squeezed by pressure. Foliation normally forms when pressure was exerted on a rock from one direction. If pressure is exerted from all directions, then the rock usually does not show foliation.

Where are foliated rocks formed?

Foliated metamorphic rocks are formed within the Earth's interior under extremely high pressures that are unequal, occurring when the pressure is greater in one direction than in the others (directed pressure).

How is a foliated rock formed?

Foliation forms when pressure squeezes the flat or elongate minerals within a rock so they become aligned. These rocks develop a platy or sheet-like structure that reflects the direction that pressure was applied. Non-Foliated Metamorphic Rocks: ... There are several ways that non-foliated rocks can be produced.