1. Weathering & Erosion: Rocks are broken down into smaller pieces (fragments) by forces like wind, water, ice, and temperature changes. This process is called weathering. The fragments are then transported away from their original location through erosion.
2. Sedimentation: These fragments, now called sediments, are deposited in a new location, usually a basin like a lake or ocean. The weight of the overlying sediments compresses the lower layers.
3. Compaction: As more sediments are deposited, the weight of the overlying layers squeezes out water and air from the spaces between the fragments. This compaction process makes the sediments more tightly packed.
4. Cementation: Dissolved minerals in the water within the sediments start to precipitate out and crystallize between the fragments. These minerals act like glue, binding the fragments together and turning the loose sediments into a solid rock.
5. Lithification: The combined processes of compaction and cementation are called lithification. This is the final stage where loose sediments become a solid rock.
Types of Rocks Formed from Fragments:
The type of rock formed depends on the size and type of fragments:
* Clastic Sedimentary Rocks: Made from fragments of other rocks. Examples include:
* Sandstone: Made from sand-sized grains
* Conglomerate: Made from gravel-sized pebbles
* Shale: Made from clay-sized particles
* Chemical Sedimentary Rocks: Formed by precipitation of minerals from water, not fragments of other rocks. Examples include:
* Limestone: Made from calcium carbonate (shells, corals)
* Rock Salt: Made from evaporated salt water
The Rock Cycle:
This is just one part of the rock cycle, a continuous process of rock formation, transformation, and destruction. Sedimentary rocks can be weathered and eroded to form new sediments, or they can be buried deep underground, melted, and transformed into metamorphic or igneous rocks.
