Sedimentary rocks are the most common rock type found on the planet comprising nearly 70 percent of all rocks. As a result they are immensely important. From unlocking historical secrets to providing the power needed to sustain the modern world these rocks are critical to mankind and have been throughout history.
Looking for clues to the ancient past, scientists are able to look to sedimentary rocks to provide the answer. These rocks are formed through layering of material over time. As plants and animals die their remains sometimes get trapped in these layers of material. In events such as volcanic eruptions there may be large scale fossil evidence since animals and plants were buried fast enough to prevent decomposition thus preserving them. Land fossils are harder to find than aquatic life since it usually takes a significant event to cover the remains fast enough so that natural forces won’t break them down.
Most fossil evidence comes from areas that were once covered in water. It is easier for fossils to form in this environment since they are more likely to avoid bacteria and scavengers. As organisms fall to the bottom of lakes, rivers, and seas they get covered in silt and sand encasing them from the forces of the outside world. Millions of years later these deposits will be changed into the rock under the forces of pressure of additional material above. During this process organic material will break down leaving only carbon behind, which makes an imprint in the surrounding rock creating fossils in the process. This offers a glimpse into what life was like on Earth millions of years ago.
The layers of rock themselves also hold immense clues about the past. The minerals that the rock is comprised of tell a lot about what the environment at the time was like. From there scientists can look at various layers of sediment from the same time period around the world to create models of what happened during the past and how animals and plants have adapted and changed over time.
The modern economy is dependent on sedimentary rocks to function. Coal and limestone which are sedimentary rocks are widely used in industry. Coal provides electrical power and has been used as a source of heat for centuries. Coal helped usher in the industrial revolution and steam power. The expansion of the United States to the west coast was greatly aided by the power of coal. Sedimentary rocks also possess other critical resources needed in them such as oil, salt, natural gas, and iron ore. Salt has long been used to season and preserve foods. Salt is an element that people must have to survive. Oil is used in many things from gas to plastics, medicine, make-up, heat, lubricants and a host of other uses. Without oil many of the modern comforts would not exist. Fertilizers used to help maximize yield and feed the modern world are derived from phosphates found in sedimentary rocks.
Sedimentary rocks have been used throughout history for construction. Sandstone has been used in building construction for thousands of years. Many of the ancient ruins in the America’s were constructed of sandstone. Limestone, another important building stone, has long been used by cutting them into building stones for walls due to their durability. Many of the buildings in the national capital are the result of construction using limestone. Today it is widely used in cement providing the foundation for the modern world. Sand and gravel have long been used in construction and are still important today. Quartz is used to create glass providing protection from elements and windows for buildings and cars. Plastering relies on gypsum and this material is widely used in construction. From the building of ancient empires to the modern nations today it can almost be assured that without sedimentary rocks it would not have been possible.
Throughout history mankind has looked to sedimentary rocks to gain understanding and obtain resources needed to survive. Without these critical resources the progression of civilization would have been extremely limited. Mankind owes its advancement and survival to the power of nature and process involved in creating sedimentary rocks.