The Rock Cycle


The rock cycle is a concept used to explain how the three basic rock types are related and how Earth processes, over geologic time, change a rock from one type into another. Plate tectonic activity, along with weathering and erosional processes, are responsible for the continued recycling of rocks.

Rocks are classified into three basic types based on how they are formed.

  • Igneous - A rock formed by the cooling and crystallization of magma (molten rock) at or below the Earth's surface.
  • Sedimentary - A rock formed as a result of the weathering process, either by compaction and cementation of rock mineral fragments, or the precipitation of dissolved minerals.
  • Metamorphic - These rocks form as existing rocks are subjected to intense heat and/or pressure, usually over long periods of time.

The rocks in display are meant to be viewed in a clockwise direction. As you walk, keep in mind that existing rocks may change through natural processes over geologic time, or event melt to form new rocks.

The Rock Cycle