The Earth goes through many cycles. Including the water cycle, the nitrogen cycle, the carbon cycle, as well as several others. One of the most important cycles that the earth experiences is the movement of rock from one type of rock to another. We call this the rock cycle.
The rock cycle includes sedimentary, igneous, and metamorphic rocks.
Igneous rocks are created when magma cools within the Earth’s crust. The magma slowly hardens into an igneous rock called basalt if it cools on top of the earth’s surface or granite if it cools further beneath the surface. During this process minerals crystallize throughout the liquid magma to create a hard rock.
Sedimentary rocks are formed through sedimentation or the deposition of sediment on the earth’s surface by weathering. This sediment is then compacted into sedimentary rock under pressure from new sediment deposits above it. Examples of sedimentary rocks include shale, sandstone, limestone, and dolomite.
Metamorphic rocks are sedimentary or igneous rocks that have been transformed by high temperature, medium to high pressure, and chemical reactions. The sedimentary rock slate is created from shale under heat and pressure while marble is formed from limestone. The igneous rock basalt can be turned into the metamorphic rock gneiss with increased heat and pressure.
The cycle starts when magma is forced up through the earth’s crust by tectonic activity where it cools and forms igneous rocks. This rock later either erodes away, shifts elsewhere, or is pushed deep within the earth where it melts and becomes magma once again. Igneous rock may also become compacted and deformed.
There is no specific path that rocks follow through the rock cycle. An igneous rock might become sedimentary or metamorphic depending on the conditions where it is found. Likewise a sedimentary rock might become either metamorphic or it may melt and become igneous again. The same goes for metamorphic rocks which can either erode, becoming sedimentary, or melt becoming igneous.
The rock cycle is an important part of our environment because many mineral resources come from sedimentary, igneous, and metamorphic rocks that have been exposed at Earth’s surface after hundreds of millions of years of shifting continents and erosion. The more we understand about how these processes occur, the better we will be able to use them for our own benefit.
