SEDIMENTARY ROCKS


Sedimentary Rocks

Sedimentary Rocks are formed by the successive deposition of sediments.

These sediments may be the debris eroded from any previously existing rock which may be igneous rock, metamorphic rock or old sedimentary rock.

Sedimentary rocks have a layered or stratified structure.

So, these rocks are also called stratified rocks.

The thickness of strata varies from a few millimeters to several meters.

Sedimentary rocks have some kind of fossil in between their strata.

Fossil is the solid component or an impression of a prehistoric animal or plant that is buried in sedimentary rock strata.

These rocks are abundant on the surface of the earth, often at shallow depths.

The individual rock particles are first broken from rocks and then transported by running water, ocean currents, and glaciers or even by the wind from one place to another.

Sedimentation is the process by which rock-forming material is deposited.

It can settle in a calmer lake or ocean waters or places where the transporter no longer has enough energy to carry them further.

These are identified as riverine, lacustrine (formed by a lake), glacial or aeolian (formed by wind) sedimentary rocks with reference to their deposition near rivers, lakes, glaciers or deserts respectively.

The sediments are loose, unconsolidated, soft rock material.

Sandstone, shale, limestone, and dolomite are examples of sedimentary rocks.

The sediments are mostly loose, unconsolidated, soft rock material, initially like sand and clay, but over time they get hardened by extreme pressure and cementation to form sedimentary rocks.

Examples of sedimentary rocks: sandstone, shale, calcareous and dolomite.

under suitable conditions sediments of various sizes get bound by cementing material.

Conglomerate is an example of such a sedimentary rock. This type of formation of consolidated material is termed as mechanically formed sedimentary rock.

The deposition of organic matter produced from plants and animals creates organic sedimentary rocks.

Coal and limestone are organic sedimentary rocks.

The sediments may also result from a chemical reaction. Examples: Gypsum, rock salt, and nitre.

Huge folded mountains of the world like the Himalayas, Andes, etc. are made up of sedimentary rocks.

All the alluvial deposits of the world are also due to sedimentary accumulations. For example, All river basins and their deltas, e.g.

Indo- Gangetic plain and Ganga-Brahmaputra delta are good examples of sedimentary accumulations.