Sedimentary rocks are formed by the sediments of rocks and remains of plants and animals. Flowing rivers carry pieces of broken rocks and deposit them in lakes or seas. Slowly these deposits settle in sea bed. Rock fragments and remains of plants and animals are squeezed together due to water pressure, and eventually they get glued together. It is a very slow process and takes millions of years to get formed. The oldest layers of these rocks are at the bottom. The three main types of sedimentary rocks are: sandstone, gypsum and limestone. Other examples are: chalk and shale.
Sedimentary Rocks
