Sedimentary rocks account for less than 5% of the total volume of rocks but are commonly observed because they cover much of Earth's surface (and much of the ocean bottom). They form from fragments of other rocks, the accumulation of biologic detritus (shells), or precipitate directly from solution. Generally, sedimentary rocks form horizontal, although they are often deformed later by burial and tectonic processes.
The type of sedimentary rocks and structures in sedimentary reflect their history.