Earths Structure And Layers Questions Medium
The major types of sedimentary rocks are clastic, chemical, and organic rocks.
1. Clastic rocks: These rocks are formed from the accumulation and lithification of fragments of pre-existing rocks or minerals. The characteristics of clastic rocks depend on the size, shape, and composition of the sediment particles. Some common examples of clastic rocks include sandstone, shale, and conglomerate. Sandstone is composed of sand-sized particles and has a gritty texture. Shale is made up of fine particles and has a layered appearance. Conglomerate consists of rounded pebbles or cobbles cemented together.
2. Chemical rocks: These rocks are formed from the precipitation of minerals from water solutions. The characteristics of chemical rocks depend on the minerals present and the conditions under which they formed. Limestone is a common example of a chemical rock, formed from the accumulation of calcite or aragonite minerals. Limestone can have various textures, ranging from fine-grained to coarsely crystalline. Another example is rock salt, which is composed of halite crystals.
3. Organic rocks: These rocks are formed from the accumulation and lithification of organic remains, such as plant or animal debris. The characteristics of organic rocks depend on the type of organic material and the conditions of deposition. Coal is a well-known example of an organic rock, formed from the remains of plant material. It has a black color, a layered structure, and can sometimes contain fossilized plant remains. Another example is chalk, which is composed of microscopic marine organisms called coccolithophores.
Overall, sedimentary rocks provide valuable information about Earth's history, as they often contain fossils and record past environmental conditions.