Earth Science

Earth Materials

Rocks and Processes of the Rock Cycle

Study Tip
Matter constantly flows and changes on the Earth. You may have already learned about the water cycle and carbon cycle. With the rock cycle, try to draw parallels between concepts to help you understand better.

The Rock Cycle

  • The rock cycle depicts how the three major rock types (igneous, sedimentary, and metamorphic) convert from one to another.
  • Most changes happen very slowly.
  • Rocks deep within the Earth are usually in the process of changing, while rocks on the surface tend to lie in place for a while before being exposed to a changing process.
Study Tip
Matter constantly flows and changes on the Earth. You may have already learned about the water cycle and carbon cycle. With the rock cycle, try to draw parallels between concepts to help you understand better.

The Three Rock Types

Igneous
Sedimentary
Metamorphic
Cooling and hardening of molten magma. Rate of cooling determines what rock forms.
Compaction and cementing together of sediments and other minerals or organic materials. Sediments are formed from weathering and erosion of preexisting rocks.
Minerals in an existing rock are changed by heat or pressure below the surface.
The composition of the magma that created it.
Sediments, broken pieces of rock-like gravel, sand, silt, clay, organic materials, and chemical precipitates.
Similar to that of igneous and sedimentary

Rock Process 1: Crystallization

  • Crystallization: The formation of mineral grains from cooling magma.
  • Magma cools either underground or on the surface and hardens into an igneous rock.
  • As magma cools, different crystals form at different temperatures. The cooling rate establishes how much time crystals will have to form. Slow cooling produces larger crystals.

Rock Process 2: Erosion and Sedimentation

  • Weathering wears rocks at the Earth’s surface down into smaller pieces, called sediments.
  • Running water, ice, and gravity all transport these sediments from one place to another by erosion
  • To form sedimentary rock, sediment must compact and cement together.
Diagram of rock formation

Earth Science

Rock Process 3: Metamorphism

  • Metamorphism: Rock is exposed to extreme heat and pressure within the Earth and does not melt
  • Metamorphism may change mineral composition and texture.
  • A metamorphic rock may have new mineral composition and/or texture.
Concept Check
  • What are the three main rock types?
  • What processes cause rocks to change? Describe in detail.