The Rock Cycle

The Rock Cycle The Rock Cycle shows how three basic rock types form Igneous, Sedimentary, Metamorphic, and illustrates how geologic processes transform one rock type into another.

The Rock Cycle Igneous Rocks Igneous Rocks originate when molten material called magma, cools and solidifies. This process, called crystallization may occur either at the Earth’s Surface or beneath the Earth’s Surface. When igneous rocks are exposed at the surface, they will undergo weathering, a process which slowly breaks down rock. The rock fragments are picked up and transported by agents of erosion such as running water, glaciers, wind, rain. Erosion: the incorporation and transportation of material by a mobile agent, such as water, wind, or ice.

The Rock Cycle Sedimentary Rock Eventually, these particles and dissolved substances, called sediment, are deposited. Next, the sediments undergo a process called lithification, meaning “conversion to rock” either by compaction or by cementation as percolating water coats the sediment with mineral matter and gradually cement the particles together. The result is sedimentary rock such as: sandstone conglomerate shale If sedimentary rock is buried deep within Earth or involved in the dynamics of mountain building, it will be subjected to great pressures and heat.

The Rock Cycle Metamorphic Rock Rocks subjected to great pressure and high heat change into metamorphic rocks. When rocks in a high temperature metamorphic environment are subjected to directional forces, they are easily transformed. When metamorphic rock is subjects to still greater heat and/or pressure changes, it may melt to create magma!

The Rock Cycle As we have seen, rocks are transformed from one type of rock to another in an unending cycle we call the rock cycle. Earth’s materials do not always follow the paths shown in the rock cycle diagram. It is just as likely that other paths will be followed. Although rocks may seem to be unchanging masses, the rock cycle shows that they are NOT. The changes, however, take time – sometimes millions or even billions of years.