Sedimentary Rocks
It is known that three quarters of the earth's surface is made up of sedimentary rocks. Whether and erosion is made up of soil and small rocks know as sediments. Sedimentary rocks form in three processes, deposition, compaction and cementation. Deposition is where sediments are found under a river, ocean or beach then collides together. Compaction is where the top layers are pressed together with the bottom layer. Cementation is the final process that glues it all together sticking the sediments together, this all happen over a long period of time.Sedimentary rocks are mainly found at the surface of environments such as oceans, beaches and rivers where there is sand that creates sediments.Like many of the other rocks part of the rock cycle,sedimentary rocks is made up of mineral crystals and some chemicals.
Five common Sedimentary Rocks
Just as we have many different types of igneous rocks we also have a variety of sedimentary rocks as well, here are a list of five sedimentary rocks: Coal, siltstone, Rock salt, flint and shale.
1.Coal
Coal is one of the many Sedimentary rocks that form on the surface of the ocean, beach and river. Being organic, it is usually located in swamp environments and forms for plant debris in those environments. Being a combustible coal is also a resourceful sedimentary rock as it is used for fuel.
2.Shale
Shale is a clastic sedimentary rock that is made up of clay weathering debris. It breaks into thin flat pieces.
3.Flint
Flint is a hard, tough chemical or biochemical sedimentary rock that breaks with a conchoidal fracture. It is a form of microcrystalline quartz that is typically called “chert” by geologists. It often forms as nodules in sedimentary rocks such as chalk and marine limestone.( 2005 - Geology.com )
4.Siltstone
Siltstone is a clastic sedimentary rock that forms from silt weathering debris.
5.Rock Salts
Rock Salts are chemical sedimentary rocks that are formed from the evaporation of ocean or saline lake waters. It's also known by the mineral name "halite". Halite is rarely found on Earth's surface, except in areas that are very desert like.