The "rock cycle."

It indicates (the book's diagram) that sedimentary rocks turn into metamorphic rocks, which in turn change into igneous rocks, which are then eroded to make sedimentary rocks.

It works in a counter-clockwise pattern, in your textbook figure.

Does the "rock cycle" really operate in any ONE particular direction?

It is a basic concept in geology. It describes the rock sin transition of the geologic processes from sedimentary to metamorphic and then to Igneous rock changes in heir chemical and physical properties. The rock cycle can break in between and operate in a reversed fashion also this transition period is said to be of primary or secondary or tertiary. This is also called the reverse geo-engineering. This transition in sedimentary begins when the unstable rocks are further destroyed or decomposed and the fragmented matter accumulates to form another material. The transition from or to metamorphic rock requires abundant heat and pressure. Water as a thermodynamic agent also plays a crucial role in their formation.