What is the difference between sediments and sedimentary rocks

Transportation is the movement of sediments or dissolved ions from the site of erosion to a site of deposition; this can be by wind, flowing water, glacial ice, or mass movement down a slope. Deposition takes place where the conditions change enough so that sediments being transported can no longer be transported e. Burial occurs when more sediments are piled onto existing sediments, and layers formed earlier are covered and compacted.

Lithification is what happens — at depths of hundreds to thousands of metres — when those compacted sediments become cemented together to form solid sedimentary rock. Organic detrital rocks form when parts of plants and animals decay in the ground, leaving behind biological material that is compressed and becomes rock. Coal is a sedimentary rock formed over millions of years from compressed plants. Inorganic detrital rocks, on the other hand, are formed from broken up pieces of other rocks, not from living things.

These rocks are often called clastic sedimentary rocks. One of the best-known clastic sedimentary rocks is sandstone. Sandstone is formed from layers of sandy sediment that is compacted and lithified. Chemical sedimentary rocks can be found in many places, from the ocean to deserts to caves. For instance, most limestone forms at the bottom of the ocean from the precipitation of calcium carbonate and the remains of marine animals with shells.

If limestone is found on land, it can be assumed that the area used to be under water. Cave formations are also sedimentary rocks, but they are produced very differently. Stalagmites and stalactites form when water passes through bedrock and picks up calcium and carbonate ions. When the chemical-rich water makes its way into a cave, the water evaporates and leaves behind calcium carbonate on the ceiling, forming a stalactite , or on the floor of the cave, creating a stalagmite.

The water drips, but the mineral remains like an icicle. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.

The Rights Holder for media is the person or group credited. Tyson Brown, National Geographic Society. National Geographic Society. For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. Ripples are commonly preserved in sedimentary rocks. Asymmetric ripples as shown above indicate flow direction,with the steep slope on the down - current direction.

Symmetric ripples form as a result of constant wave energy oscillating back and forth. If we look at various environments now present on Earth, we can find characteristics in the sediment that are unique to each environment.

If we find those same characteristics in sedimentary rocks, it allows us to interpret the environment of the past. Each environment has its own energy regime and sediment delivery, transport and depositional conditions that are reflected in the sediment deposited. Sedimentary Environments can be divided into the following.

We will cover most of these environments in more detail later in the course. For now familiarize yourself with each of these by reading pages to in your text. Throughout geologic history sea level has risen and fallen by as much as a few hundred meters many times. These changes are the result of changes earth's climate or changes in the shape of the sea floor as a result of tectonics.

When sea level rises, the coast migrates inland. This is called a Transgression. Beach sand gets buried by marine sediments and the sea floor subsides due to the weight of the sediment. During a transgression, the beach sand forms an extensive layer, but does not all have the same age. When sea level falls, the coast migrates seaward.

This is called a Regression. The sedimentary sequence then repeats itself in a vertical sense as the sedimentary environment migrates back and forth. LIthification of sediment into sedimentary rocks takes place after the sediment has been deposited and buried. The processes by which the sediment becomes lithified into a hard sedimentary rock is called diagenesis and includes all physical, chemical and biological processes that act on the sediment.

The first step in diagenesis is the compaction of the sediment and loss of water as a result of the weight of the overlying sediment. Compaction and burial may cause recrystallization of the minerals to make the rock even harder.

Fluids flowing through the rock and organisms may precipitate new minerals in the pore spaces between grains to form a cement that holds the sediment together. Common cements include quartz, calcite, and hematite.

Other conditions present during diagenesis, such as the presence of absence of free oxygen may cause other alterations to the original sediment. In an environment where there is excess oxygen Oxidizing Environmen t organic remains will be converted to carbon dioxide and water. In an environment where there is a depletion of oxygen Reducing Environment , organic material may be transformed to solid carbon in the form of coal, or may be converted to hydrocarbons, the source of petroleum.

Diagenesis is also a response to increasing the temperature and pressure as sediment gets buried deeper. As temperature increases beyond about o C, we enter the realm of metamorphism, the subject of our next discussion.

Sediment and Sedimentary Rocks. Sedimentary Rocks Rivers, oceans, winds, and rain runoff all have the ability to carry the particles washed off of eroding rocks.

Clastic Sediments and Sedimentary Rocks. The formation of a clastic sediment and sedimentary rocks involves five processes: Weathering - The first step is transforming solid rock into smaller fragments or dissolved ions by physical and chemical weathering as discussed in the last lecture. Erosion - Erosion is actually many processes which act together to lower the surface of the earth. In terms of producing sediment, erosion begins the transportation process by moving the weathered products from their original location.

This can take place by gravity massmovement events like landslides or rock falls , by running water. Erosion overlaps with transportation. Transportation - Sediment can be transported by sliding down slopes, being picked up by the wind, or by being carried by running water in streams, rivers, or ocean currents. The distance the sediment is transported and the energy of the transporting medium all leave clues in the final sediment that tell us something about the mode of transportation.

Deposition - Sediment is deposited when the energy of the transporting medium becomes too low to continue the transport process. In other words, if the velocity of the transporting medium becomes too low to transport sediment, the sediment will fall out and become deposited.

The final sediment thus reflects the energy of the transporting medium. Lithification Diagenesis - Lithification is the process that turns sediment into rock.

The first stage of the process is compaction. Compaction occurs as the weight of the overlying material increases. Compaction forces the grains closer together, reducing pore space and eliminating some of the contained water.

Some of this water may carry mineral components in solution, and these constituents may later precipitate as new minerals in the pore spaces. This causes cementation, which will then start to bind the individual particles together. Conglomerate or Breccia depends on rounding. Textures of Clastic Sedimentary Rocks When sediment is transported and deposited, it leaves clues to the mode of transport and deposition.

Examples Beach deposits and wind blown deposits generally show good sorting because the energy of the transporting medium is usually constant. Stream deposits are usually poorly sorted because the energy velocity in a stream varies with position in the stream and time. Sediment Maturity Sediment Maturity refers to the length of time that the sediment has been in the sedimentary cycle. Types of Clastic Sedimentary Rocks We next look at various clastic sedimentary rocks that result from lithification of sediment.

Conglomerates and Breccias Conglomerate and Breccia are rocks that contain an abundance of coarse grained clasts pebbles, cobbles, or boulders. Sandstones A Sandstone is made of sand-sized particles and forms in many different depositional settings. Mudrocks Mudrocks are made of fine grained clasts silt and clay sized. Biochemical and Organic Sediments and Sedimentary Rocks Biochemical and Organic sediments and sedimentary rocks are those derived from living organisms. Among the types of rock produced by this process are: Biochemical Limestone - calcite CaCO 3 is precipitated by organisms usually to form a shell or other skeletal structure.

Chemical Sediments and Sedimentary Rocks Dissolved ions released into water by the weathering process are carried in streams or groundwater. Among these are: Evaporites - formed by evaporation of sea water or lake water.

There are many varsities of such chert that are given different names depending on their attributes, For example: Flint — Black or gray from organic matter. Sedimentary Structures As mentioned previously, all stages of the sedimentary cycle leave clues to processes that were operating in the past.

Stratification and Bedding Because sediment is deposited in low lying areas that often extend over wide areas, successive depositional events produce layers called bedding or stratification that is usually the most evident feature of sedimentary rocks. Rhythmic Layering - Alternating parallel layers having different properties.

Sometimes caused by seasonal changes in deposition Varves. Cross Bedding - Sets of beds that are inclined relative to one another. The beds are inclined in the direction that the wind or water was moving at the time of deposition.