Sedimentary Rocks2006 Prentice Hall Science Explorer- Earth ScienceLiz LaRosa http://www.middleschoolscience.com 2009Images from Geology.com unless otherwise noted

Formation of Sedimentary RockMost sedimentary rocks are formed through a series of processes: erosion, deposition, compaction and cementation.

ErosionDestructive forces are constantly breaking up and wearing away all the rocks on Earths surface.

These forces include heat and cold, rain, waves, and grinding ice. These forces of erosion form sediment which are small solid pieces of material that come from rocks or living things.

In erosion, running water, wind, or ice loosen and carry away fragments of rock.

DepositionEventually, the moving water, wind or ice slows and deposits the sediment in layers.

Deposition is the process by which sediment settles out of water or wind carrying it.

CompactionThe process that presses sediments together is compaction. Thick layers of sediment build up gradually over millions of years. These heavy layers press down on the layers beneath them. The weight of new layers further compacts the sediments, squeezing them tightly together. The layers often remain visible in sedimentary rock.

CementationWhile compaction is taking place, the minerals in the rock slowly dissolve in the water.

Cementation is the process in which dissolved minerals crystallize and glue particles of sediment together. In cementation, dissolved minerals seep into the spaces between particles and then harden.

StratificationSedimentary Rocks are formed at or near the Earths surface.No heat and pressure involvedStrata layers of rock

Stratification the process in which sedimentary rocks are arranged in layersStratification

http://www.fi.edu/fellows/payton/rocks/create/sediment.htm

Sedimentary rock is formed by erosionSediments are moved from one place to anotherSediments are deposited in layers, with the older ones on the bottomThe layers become compacted and cemented togetherSummary: Formation of Sedimentary Rock

Types of Sedimentary RocksGeologist classify sedimentary rocks according to the type of sediments that make up the rock.

There are three major groups of sedimentary rocks: clastic rocks, organic rocks, and chemical rocks.

A clastic rock is a sedimentary rock that forms when rock fragments are squeezed together.

An organic rock forms where the remains ofplants and animals are deposited in thick layers.

Chemical rock is formed when minerals that aredissolved in a solution crystallize.

Uses of Sedimentary RockPeople have used sedimentary rock throughout history for many different purposes, including building materials and tools.ExamplesArrowheadsSandstone and Limestone used in building materialsLimestone is also used in making cement and steel.