Sedimentary Rocks

There are three types of sedimentary rocks.

Clastic, Chemical,Organic,

Sedimentary rock forms from these processes:

Compaction: sediments are pushed together and as a result, water and air are squeezed out. Cementation: water passes through the sediments and dissolved minerals left behind act as a cement to hold the sediments together. Precipitation: minerals clump together and fall out of solution Evaporation: Water evaporates and leaves dissolved minerals behind.

Most sedimentary rock forms under water.

Ex. Limestone, halite

Clastic:

Formed from fragments of other rocks which have been weathered and eroded Classified by the size of the sediments (coarse-pebbles or larger, medium-sand sized, or fine-clay or silt sized) Ex. Sandstone (sand), shale (silt or clay), conglomerate (round pebbles), and brecci

Chemical:

Formed from minerals that were once dissolved in water. Either the minerals "settle" out of the water (precipitates) or the water evaporates leaving the minerals behind (evaporites) Classified by their mineral composition Ex. Chemical Limestone (CaCO3), gypsum (CaSO4), halite (NaCl)

Organic:

Formed from the remains or traces of animals and/or plants Ex. Coal (plants), chalk (animal skeletons), organic limestone (shells-CaCO3)

What is sediment?

Fragments that result from the breaking (weathering) of rocks, minerals, and organic matter. Ex. Gravel, clay, silt, pebbles, sand, mud, shells, dirt

Limestone

Limestone is a rock that is composed primarily of calcium carbonate. It can form organically from the accumulation of shell, coral, algal and fecal debris. It can also form chemically from the precipitation of calcium carbonate from lake or ocean water. Limestone is used in many ways. Some of the most common are: production of cement, crushed stone and acid neutralization

Sedimentary Rocks

Made from an accumulation of various types of sediments

Rock Salt

Rock Salt is a chemical sedimentary rock that forms from the evaporation of ocean or saline lake waters. It is also known by the mineral name "halite". It is rarely found at Earth's surface, except in areas of very arid climate. It is often mined for use in the chemical industry or for use as a winter highway treatment. Some halite is processed for use as a seasoning for food.

Features of Sedimentary Rocks

Stratification: (aka. Layering) occurs when there is a change in the kind of sediment deposited. Ex. Grand Canyon

Ripple marks:

formed from the action of wind or water on sand (seen in sandstone)

Fossils:

remains or traces of plants and/or animals