Regional metamorphic rocks are formed when large areas of Earth's crust are subjected to intense heat and pressure over a long period of time. This usually occurs during mountain building events, where tectonic plates collide.

Here are some key features of regional metamorphism:

* Large scale: The metamorphic process affects vast areas, unlike contact metamorphism which is localized.

* High pressure and temperature: These conditions are typically higher than those found in contact metamorphism.

* Directed pressure: The pressure is not uniform, but comes from the weight of overlying rocks and tectonic forces. This results in a foliation, or layered texture, in the rocks.

* Duration: Regional metamorphism occurs over extended periods, allowing for significant changes in mineral composition and texture.

Examples of regional metamorphic rocks:

* Schist: A medium-grade metamorphic rock with a well-developed foliation.

* Gneiss: A high-grade metamorphic rock with a distinct banding of light and dark minerals.

* Phyllite: A fine-grained metamorphic rock with a silky sheen.

In summary: Regional metamorphic rocks are formed over large areas due to high pressure and temperature, often associated with tectonic plate collisions. They exhibit distinct textures, such as foliation, and are often associated with mountain ranges.