Why is sedimentary rock layered?
Sedimentary rock is layered because the rock is composed of lithified sediments. Sediments are carried wind wind, water, ice, and gravity until they no longer can move due to friction and gravity. Differences seen in individual layers may be because of seasonal changes in depositional materials (springtime flooding), changes in the sediments due to a change in the erosional course of rivers and streams, environmental catastrophes such as flooding and large fires, and a whole host of other influences on the supply of material that make up the individual rock stratum.