Download Pieces of rocks, minerals, remains of living things, and dissolved

Pieces of rocks, minerals, remains of living things, and
dissolved minerals that come out of water (such as lime) are
all kinds of sediments. Sedimentary rocks are rocks
formed when sediments are pressed and cemented together
naturally, over millions of years.
Sedimentary rocks may be formed from small pieces of rock,
shells, soil, fossils, and the remains of plants. Rocks are
broken down by a process called weathering. The small
parts of rock may be carried by wind or water to a new
location during the process of erosion.
The remains of living things may be deposited at the bottom of a lake, river, or pond.
Sedimentary rocks often contain fossils. Layers of different types of sediment build
up over many thousands of years. These layers are pressed together. The pressing
down is called compaction. Over many thousands of years, water is pressed out
and the layers stick together. The process that results in the layers being stuck
together is called cementation.
Sometimes, it is possible to identify the sediments in
sedimentary rocks. Some large particles of rock or shell
may be visible. Sometimes the particles are too small to
see without a microscope. Fossils or imprints of plant
and animals can be seen in some sedimentary rocks.
Most of the rocks found in the world are sedimentary
rocks. Examples include sandstone, limestone, and
halite.