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Sedimentary rock

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Sedimentary Rocks
Sandstone formation called Delicate Arch at the Arches National Park Utah

Sedimentary Rocks are a type of rock that is formed by the accumulation of sediments (matter that settles to the bottom of a liquid). Sedimentary Rocks cover about 75 percent of the Earth's surface. Popular rocks include Coal, Sandstone, Conglomerate, and Limestone; which will be explained in greater detail. The formation of sedimentary rocks and the flood are important to the topic. The three types of Sedimentary Rocks they all have a unique difference between each other. These can be identified through many different ways and have been discovered all over the world. [1]

Sedimentary rocks are composites of pre-existing rocks that have been weathered and eroded, or pieces of once-living organisms. Most fossils are found in sedimentary rocks of which there are three main types: sandstone, limestone, and shale. Most of these rocks started as sediments carried in fluid, that were deposited as the current slowed. When the sediments are buried and dried, they become cemented to form rock. Most sedimentary rocks become cemented together by minerals and chemicals or are held together by electrical attraction; some, however, remain loose and unconsolidated.

Sedimentary rocks often have distinctive layering or bedding like those visible at the Grand Canyon. The layers of sediments are normally parallel or nearly parallel to the Earth's surface when they are formed. If they are found at high angles to the surface or are twisted or broken, some kind of movement must have occurred since the rock was formed. Many of the picturesque views of the desert southwest show mesas and arches made of layered sedimentary rock, such are those in Arches National Park pictured at right.

Although sedimentary rocks can form today, it is believed by creation scientists that the majority of the Earth's strata was formed catastrophically during the Biblical flood of Noah. On the otherhand, uniformitarian geologists hold to the view that most sedimentary rocks were formed slowly and gradually at current rates of erosion and deposition.

Formation of Sedimentary Rocks

Erosion traveling pieces of rocks

The formation of Sedimentary Rocks occurs in five step process: Weathering, Erosion, Deposition, Compaction and Cementation.

  • Weathering: Defined as the action of weather altering the color or texture of the object, there are two types of weathering, which are physical and weathering. Physical involves weakening or breaking up rocks when on the surface of earth; for example the amount of rainfall or animals digging up holes on the surface can crush and separate the rocks. Chemical weathering forms through water and acid forming inside of water, they cause the change of shape and color of the rock. Examples include reactions with rocks and oxygen which produce oxidation; and when carbon dioxide break down with water forming carbonic acid.
  • Erosion: The process after Weathering is called Erosion. Defined as process where broken down pieces of rocks are moved through wind, water, ice or gravity. Water is the most popular way of transportation, for example small pieces of rocks travel through rivers to places as seen in the picture.
  • Deposition: The process after Erosion is Deposition. Defined as process where rocks are added to surface. After Erosion transports the rocks, deposition causes the rocks to stop or come to a rest, and are then deposited horizontally.
  • Compaction/ Cementation: The process after Deposition is Compaction/ Cementation. After many rocks are complied during deposition, this process connects, glues or sticks the rocks together.[2]

The process of Compaction and Cementation show us that the flood in Genesis caused the formation of rock layers. The flood starts out the God being angry with the wicked and sinful nature of the people. Noah and his family were the only people God saw that loved him. God instructed Noah to build an ark, and take his family, and the animals. He told him that he is preparing a massive flood. After a year of the flood, God promised to never send a flood onto the earth. The floodwater would have transported mass amounts of sediments throughout the earth. Sediments are found in many different areas; and we know that the flood was a worldwide catastrophe, which can explain the discovery of sedimentary rocks in different areas. The rapid burial of fossils before decay or decomposition, show proof of the flood. The death pose shows animals struggling and fighting against a massive flood, because of their unique posture. We even see fossils of marine animals on rocks on the Grand Canyon. We should believe what Genesis says about the flood not the untrustworthy scientist, because the geological evidence fits perfectly with the word of God. [3].

Types of Sedimentary Rocks

There are three types of Sedimentary Rocks Clastic, Chemical and Organic. They are all similar and different in their own ways



Clastic Sedimentary Rocks are defined as rocks formed by mechanical weathering debris. They are formed through breaking down rocks and compaction of sediments. They are the only members of rocks that contain fossils, shown when the rock was just formed. Their are many types of Clastic Rocks such as breccia, conglomerate, sandstone and siltstone. They are all named according to the sizes of the particles. Breccia which is seen on the image is 2mm-64mm angular grains; They form through the accumulation of debris flowing. Conglomerate 64mm to 256mm rounded grains; they form through accumulation of debris. They are extremely similar to Breccia because of how they are formed; although they are different in the shape and size.

Clastic sedimentary rocks may have particles ranging in size from microscopic clay to huge boulders. Their names are based on their clast or grain size. The smallest grains are called clay, then silt, and sand. Grains larger than 2 millimeters are called pebbles. Shale is a rock made mostly of clay, siltstone is made up of silt-sized grains, sandstone is made of sand-sized clasts, and conglomerate is made of pebbles surrounded by a matrix of sand or mud.[4]

Types of Clastic Sedimentary Rocks:


Organic Sedimentary Rocks (or biologic) are defined as rocks formed through deposition and formation of debris. This is similar too how other sedimentary rocks are formed except they're formed through plant and animal debris. Different types of Organic rocks are coal, dolomites and even limestone. Dolomites are composed mainly of minerals and form mud limestone. Limestone are composed mainly of calcium carbonate. These two rocks are similar in that they have same color ranges and strength. They behave similarly when reacting to heat and pressure [5]

Organic sedimentary rocks form when large numbers of living things die, pile up, and are compressed and cemented to form rock. Accumulated carbon-rich plant material may form coal. Deposits made mostly of animal shells may form limestone, coquina, or chert.[4]

Types of Biological Sedimentary Rocks:


Chemical Sedimentary Rocks: Defined as rocks formed by precipitation of minerals through water. This occurs during the warm spring temperature, and forms a crystalline structure. Iron, chert, flint and limestone all are Chemical Sedimentary Rocks. Iron is formed through a chemical reaction of Iron and oxygen. They are heavily involved in many of the things we use today such as cars, ships, buildings, and many more. Limestone are a complicated type of sedimentary rock. Limestone can be identified by it's unique colors, and can be found in Caves or underwater. Such as in the Indian and Pacific oceans, or Persian and Mexican gulf. Limestone and Iron are similar in that they involve in production of steel.

Chemical sedimentary rocks are formed by chemical precipitation. The stalactites and stalagmites you see in caves form this way, so does the rock salt that table salt comes from. This process begins when water traveling through rock dissolves some of the minerals, carrying them away from their source. Eventually these minerals can be redeposited, or precipitated, when the water evaporates away or when the water becomes over- saturated with minerals.[4]

Types of Chemical Sedimentary Rocks:

Economic and Historical Impact

Coal Production graph

Although Sedimentary Rocks play a big role on the Earth today, they also impact the economical and historical world.

Sedimentary Rock such as iron and coal play a role in the economy, and production of materials. For example, Iron plays a role in production of steel, the steel is used to create bicycles, cars, ships and more. Steel accounts for a large amount of jobs in the United States. Coal is one of the most important fossil fuels with oil and natural gas. Coal is known for production of electricity. During the early and mid 1900's demand for natural gas grew, and coal became very important, as seen on the image. Coal is still important in our world today. Sedimentary Rocks also tell us things about the history. Some rocks like the metamorphic rocks contain fossil evidence that show the history of the fossil. Sedimentary Rocks have a lot of uses. [6]


Introduction to Sedimentary Rocks....


  1. What are Sedimentary Rocks Geology. Pictures of Sedimentary Rocks. No author date accused 28 Nov, 2018.
  2. No AuthorSedimentary Rocks Science Daily. No Date.
  3. Dr. Andrew A. Snelling Geological Evidences for the Genesis Flood "Answers in Genesis". Answers in Genesis. Dec 26, 2007.
  4. Cite error: Invalid <ref> tag; no text was provided for refs named USGS
  5. Alden, Andrew. What are sedimentary rocks? Thought Co. Web. April 15, 2018. (last modified.).
  6. Louis,Robert. Sedimentary Rocks Encyclopedia Britannica. Web. October 16, 2018. (last updated).