Sedimentary Rock

                      By Mr_dad_digvijay



Sedimentary Rock
An example of a sedimentary rock, which is, by definition, composed of many, smaller rocks.

Sedimentary rocks are formed on or near the Earth’s surface, in contrast to metamorphic and igneous rocks, which are formed deep within the Earth. The most important geological processes that lead to the creation of sedimentary rocks are erosion, weathering, dissolution, precipitation, and lithification.


Erosion and weathering include the effects of wind and rain, which slowly break down large rocks into smaller ones. Erosion and weathering transform boulders and even mountains into sediments, such as sand or mud. Dissolution is a form of weathering—chemical weathering. With this process, water that is slightly acidic slowly wears away stone. These three processes create the raw materials for new, sedimentary rocks.


Precipitation and lithification are processes that build new rocks or minerals. Precipitation is the formation of rocks and minerals from chemicals that precipitate from water. For example, as a lake dries up over many thousands of years, it leaves behind mineral deposits; this is what happened in California’s Death Valley. Finally, lithification is the process by which clay, sand, and other sediments on the bottom of the ocean or other bodies of water are slowly compacted into rocks from the weight of overlying sediments.


Sedimentary rocks can be organized into two categories. The first is detrital rock, which comes from the erosion and accumulation of rock fragments, sediment, or other materials—categorized in total as detritus, or debris. The other is chemical rock, produced from the dissolution and precipitation of minerals.


Detritus can be either organic or inorganic. 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.

 Sediment is solid material that is moved and deposited in a new location. Sediment can consist of rocks and minerals, as well as the remains of plants and animals. It can be as small as a grain of sand or as large as a boulder.


Sediment moves from one place to another through the process of erosion. Erosion is the removal and transportation of rock or soil. Erosion can move sediment through water, ice, or wind.


Water can wash sediment, such as gravel or pebbles, down from a creek, into a river, and eventually to that river's delta. Deltas, river banks, and the bottom of waterfalls are common areas where sediment accumulates.

Plant Fossil
Sediment has turned this ancient plant into a fossil. The imprint of organisms that are quickly covered by sediment (such as mud, dust, or sand) can be preserved as fossils.


Glaciers can freeze sediment and then deposit it elsewhere as the ice carves its way through the landscape or melts. Sediment created and deposited by glaciers is called moraine.

Glacial Sediment
This lake in Alberta, Canada, is dramatically colored by glacial sediment. Glaciers carve away rock and soil as they slice through the landscape. The glacial sediment in this lake is very fine (sometimes called "rock flour") and reflective,


Wind can move dirt across a plain in dust storms or sandstorms. Sand dunes are made of rocky sediment worn down by wind and collision with other sand particles.


Sediment is important because it often enriches the soil with nutrients. Areas rich in sediments are often also rich in biodiversity. Sedimentary soil is usually better for farming. Deltas and river banks, where much sediment is deposited, are often the most fertile agricultural areas in a region.


For thousands of years, the Nile River flooded yearly and brought with it 4 million metric tons (4.4 million short tons) of nutrient-rich sediment. The banks of the Nile are still Egypt's richest agricultural land.


Sedimentary Rock

Swirling TextureOver millions of years, layers of sediment may build up and harden into sedimentary rock like this sandstone at Kaleidoscope Ridge, Arizona. Sandstone forms as tiny grains of sand harden into a single mass.

Over millions of years, layers of sediment may build up and harden into sedimentary rock. Some of the many forms of sedimentary rock include sandstone, rock salt, and coal.

Sandstone forms as sand hardens. For centuries, sandstone has been mixed with sticky cement to form concrete. Concrete is an important construction material used for many buildings and

Banks Peninsula

An apron of greenish-blue, sediment-laden waters surrounds the Banks Peninsula in Christchurch, New Zealand. Sediment from the peninsula moves from one place to another through erosion. Erosion is the removal and transportation of rock or soil through water or wind.


Rock salt, also known as halite, forms as oceans evaporate. Oceans are made of salt water. When the water enters the atmosphere as vapor, it leaves the salt behind. The Bonneville Salt Flats, in the U.S. state of Utah, are flat desert areas covered by a layer of rock salt sediment. Lake Bonneville, the ancient sea that once covered the area, has long since evaporated. oadsporated.

Coal is a sediment that is made up of hardened plant debris. Coal, present on every continent except Antarctica, is found on the sites of former swamps and wetlands.


Sediment that is light enough to be carried by water without touching the stream bed is called suspended sediment, and is visible as cloudy or milky areas of water.