Igneous rock that is uncovered to the Earth’s surface will undergo destruction (erosion) by the influence of weather, then it is transported by natural power such as water, winds or glaciers and it got sediment in another places, so sedimentary rocks formed.
According to the formation process, sedimentary rocks are separated into:
a. Clastic or Mechanic Rock.
It is formed from the clump of larger rock that is carried from the slope of mountain, through the rain water then it is carried by river flow and then it is got sediment in a downstream region in the form of sand the chemical composition of which is still same with original rock. It means the sedimentation does not undergo a chemical process, but only a mechanical process.
The example of clastic rock are: brexi rock, conglomerate rock, sand and clay.
b. Chemical Rock.
c. Organic Rock.
It is formed from the accumulations of animal and plant remains.