These sandstone spires may eventually be transformed to another type of rock.
The rock cycle is the term scientists use to describe the long, slow processes by which rocks of one type are transformed to another. The rock cycle runs constantly, so rocks are continually changing.
Rock Types
Earth scientists divide rocks into three general types based on the environment in which they form. These three types are igneous, metamorphic and sedimentary. Any rock can be classified as one of these types based on the minerals present and the shapes and relationships of the grains.
New Rocks from Old
Igneous rocks crystallize, or cool, from molten liquid called magma, which is merely older rocks that have been melted. Sedimentary rocks form from particles eroded from older rocks. Metamorphic rocks form when an older rock is squeezed and heated deep underground, but not heated enough to melt.
The Endless Cycle
The rocks that make up the Earth's crust are always slowly changing. A granite (igneous) peak in the Rockies slowly crumbles, and the bits wash downstream to the Mississippi Delta, to be deposited as sand. The sand becomes sandstone (sedimentary). In millions of years, the sandstone may become so deeply buried that it almost melts, becoming quartzite (metamorphic).
Not Simply a Circle
In time, any rock type can become another rock of any type. Sand eroded from a ledge of sandstone may become part of another, younger sandstone. A granite body that has never seen daylight may re-melt to become a different igneous rock. The cycle does not run in just one direction, and even loops back on itself. (reference 3)
Tags: rock cycle, another rock, eroded from, older rocks, rock type
