Sedimentary rocks have a wide variety of uses, making them extremely important. Types of sedimentary rocks have surprising physical, everyday uses and uses in construction. They are also useful to geologists and other scientists with interest in studying the earth. Organic sedimentary rocks, like coal, are energy resources. Seventy percent of the rocks on earth are sedimentary.
Firstly, without sedimentary rocks we would not have chalk or salt and we would need to find alternate building material for most of the buildings in existence. Sandstone has been used around the world in construction, especially in regions where the stone is common. It is easy to work with. The Cliffe Castle Museum in West Yorkshire, England is composed completely of sandstone. Limestone is another important building stone, and is also what chalk is made of. Shale, another easily worked material, is used as filler in many paints and also as an aggregate in road construction. Gypsum is a major ingredient in sheetrock and plaster. Halite, commonly used as table salt, is a chemical sedimentary rock. Sedimentary rocks are also home to the vast majority of the world’s iron ore deposits, making them indirectly useful as well. The commercial importance of sedimentary rocks is visible everywhere.
Coal is one of the most important resources in the world today. It is a combustible rock, and along with oil and natural gas, is a fossil fuel used to generate electricity. In addition to electricity, it is also used for heating in various types of manufacturing and most factories are powered by coal. When heated, coal produces gas and residues that are used to make plastics, various synthetic materials, and medicines. Coal is an organic sedimentary rock, made mainly of plant material. It takes millions of years to form. Roughly fifty feet of plant material is needed to make a five-foot seam of coal over a period of several thousand years. Plant material also builds up very slowly. Although created naturally, coal is not considered a renewable resource.
For scientists, sedimentary rock provides clues about the history of the earth, and sedimentary rock is also the type of rock containing fossils. Scientists study the layers of sediment that have accumulated over time, taking into account the erosion and weathering that has also occurred. These studies shed light on the climate as well as environment when they formed, and the composition of the land at the time. They provide a rough timeline – the rock layers farthest down are the oldest and get progressively younger as they progress toward the surface. The layers in which fossils are found indicates the time period in which they lived. Sedimentary rock always formed where there was once some source of water – finding fossils and sedimentary rock in deserts indicates that the area was not always a desert.
Making up so much of the earth, it is no wonder that we have found so many uses for sedimentary rock. Ancient humans found uses for sedimentary rock and we still use these rocks commercially today. They are a very important part of our lives, from small things like salt for our food, to our buildings, to our energy. Scholarly, sedimentary rocks are also a very important source of valuable information about the history of earth.