Geology Chapter 6: The Rock Cycle

Rock Basics

• Rock is a natural solid composed of one or more minerals and organic matter.
• Rock Cycle describes the continuous transformation of rock types: sedimentary, igneous, and metamorphic.

Sedimentary Rock

• Formed through weathering and erosion, deposition, compaction, and cementation.
• Sediment consists of broken rock and mineral fragments resulting from weathering.
• Any type of rock can eventually become sedimentary if exposed at the Earth's surface.
• Fossils are typically found within sedimentary rocks.

Weathering and Erosion

• Weathering refers to the breakdown of rock caused by natural forces like water and temperature changes.
• Erosion is the movement of sediment by wind and water.

Deposition, Compaction, and Cementation

• Deposition is the accumulation of sediment in layered formations.
• Compaction squeezes sediment layers together due to the weight of overlying materials.
• Cementation binds sediment into solid rock.

Examples of Sedimentary Rocks

• Breccia: Contains angular fragments.
• Shale: Composed of fine particles, often layers.
• Sandstone: Made of sand-sized particles.

Igneous Rock

• Igneous rocks form from the cooling and solidification of hot molten rock (magma).
• Extrusive igneous rock forms near or at the Earth's surface during volcanic eruptions and cools quickly; examples include pumice and obsidian.
• Intrusive igneous rock forms from magma that cools slowly beneath the Earth's surface, resulting in rocks like granite.

Black Sand Beach

• Punalu'u beach in Hawaii features black sand created from lava that cooled rapidly in the ocean, breaking into sand-sized particles.

Metamorphic Rock

• Formed from sedimentary or igneous rocks that undergo change due to heat and pressure.
• Examples include slate (from shale) and marble (from limestone).

Key Processes and Concepts

• The rock cycle illustrates how rocks transform from one type to another through natural processes.
• Intrusive igneous rocks often rise to the surface due to plate tectonics and uplift forces.
• Heat and pressure are primary agents that transform sedimentary and igneous rocks into metamorphic rocks.
• Any rock type can ultimately become sedimentary through weathering and accumulation processes.