Question

Rocks formed from remains of once-living plants and animals are called :
A. Organic sedimentary rock
B. Chemical sedimentary rock
C. Inorganic sedimentary rock
D. clastic sedimentary rock

Answer 1

Hint:When sediment is deposited out of air, wind, gravity or water flows carrying of the particles in suspension, also when weathering and erosion breakdown a rock into loose materials in a source area then sedimentary rocks are formed, when a large number of living things died and compressed and cemented then organic sedimentary rocks are formed.


Complete answer:
First of all we will take a look on the options given in the question :
A. Organic sedimentary rock : Animals and plants died and compressed into the earth
When it occurs in large amounts organic sedimentary rocks are formed by the cementation of dead elements animals and plants.
Example : fossil ferrous limestone and coal.
B. Chemical sedimentary rock : When minerals constituent in solution become supersaturated and inorganically precipitate then chemical sedimentary rocks are formed chemical rocks are not made up of pieces of sediment instead they have a mineral crystal of element minerals that are dissolved in water.
Example : limestone.
C. Inorganic sedimentary rock : Inorganic sedimentary rocks are made of Broken pieces of other rocks. These rocks are not made up of living things.
Example : rocks salt, dolomite are the examples of inorganic sedimentary rock
D. Clastic sedimentary rock : Clastic sedimentary rocks are made up of broken pieces or clusters of older weathered and eroded rocks.
These types of rocks can be classified based on grain size, clusters, composition and texture.
So by the definition of all sedimentary rocks we can conclude that only organic sedimentary rocks are formed from remains of once-living plants and animals.


Hence the correct option is (A).


Note: When small particles of rocks are transported by river then many sedimentary rocks are formed, clastic sediment grains can be round angular or in between, chalk is a sedimentary carbonate rock.