Rock materials can change through multiple geological pathways.
Key knowledge
The rock cycle connects igneous, sedimentary and metamorphic materials through processes such as melting and crystallization, weathering and sediment formation, and alteration by heat, pressure or fluids. It has multiple pathways rather than a required starting point or sequence.
Conditions and scope
Metamorphism changes pre-existing rock without bulk melting; crystallization after melting belongs to an igneous pathway.
A cycle diagram does not specify the rate or detailed history of a particular rock.
Sources · 3
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
USGS's documented rock types, transformation pathways and metamorphism distinction; no sample identification or dating.
2026-10-10 · English process scope checked against the USGS rock-cycle sections and metamorphic-rock FAQ.
Foundational review
2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.
Sources from other places
Agreement within this scope
Formation and transformation of the three main rock classes.
Rock cycling offers multiple pathways rather than one required sequence.
The rock cycle connects igneous, sedimentary and metamorphic materials through processes such as melting and crystallization, weathering and sediment formation, and alteration by heat, pressure or fluids. It has multiple pathways rather than a required starting point or sequence.
Earth's lithosphere is divided into plates that move relative to one another. Divergence can create new oceanic lithosphere, convergence can involve subduction, and many earthquakes and volcanoes occur near plate boundaries.
Plate settings can connect metamorphism, subduction and magma-related rock formation.
Mineral species are distinguished by composition and ordered atomic structure. Useful identification properties include hardness, cleavage, streak, lustre and density. Several properties together provide stronger identification than colour alone, which can vary with composition, inclusions or surface appearance.
Mineral structure and composition describe constituents of geological materials.
In introductory geology, a mineral is a naturally occurring inorganic solid with characteristic composition and ordered internal structure. A rock is an aggregate of one or more minerals or undifferentiated mineral material. Rock identity therefore involves constituent materials and their arrangement, rather than requiring a single mineral species or one pure chemical formula.
Rock-cycle processes transform aggregate materials and textures without requiring every rock to be one pure mineral.
Geologists use physical and chemical processes observed today to interpret the rock record. This methodological principle, often called uniformitarianism, does not require constant process rates, identical environments or exclusively gradual events. Ancient atmospheric chemistry and rare catastrophic impacts can differ from everyday modern observations and must be constrained by evidence.
Rock transformations observed today can inform historical interpretation when past conditions and alternative mechanisms are considered.