RocksGroup4

media type="file" key="rocks.3gp" =__SEDIMENTARY ROCK FACTS__=

**. Many fossils are found in sedimentary rock.**
=__HOW THEY ARE FORMED__= 

Sedimentary rocks are made out of sediments, I sed- it and -I ment it!
==Sedimentary rocks are those formed from the compaction and cementation of fragments of pre-existing rocks or plant and animals remains ( fossils). Also sedimentary rocks are born cool at the Earth's surface, mostly under water. That is why we find dinosaur fossils and early sea life. For millions of years, pieces of our earth have been eroded (broken down) and worn away==  ===by wind and water. These little bits of our earth are washed downstream where they settle to the bottom of the the body of water they so happen to be in. Layer after layer of eroded earth is deposited on top of each other. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock. lithification is the compaction and cementation of rock fragments that form sediments from rocks. sandstone is made up of sandstone particles-shale is going to feel smooth made of compacted mud. chemical (crystalline) sedimentary rocks formed from the precipitation of a mineral solution the main causes for dissolved minerals to precipitate or drop out of the water, is an evaporation.===


 * How to tell if YOUR rock is Sedimentary

** **May react with acid **Often has layers, flat or curved **Usually composed of pieces cemented or pressed together **Has great color variety **Particle size may be the same or vary **Usually has pores between pieces **May have cross-bedding, mud cracks, worm burrows, raindrop impressions
 * Often contains [| fossils]

= __IGNEOUS ROCKS__ =

 Igneous rock is formed by [|magma] (molten rock) cooling and becoming solid. Igneous rock may form with or without [|crystallization], either below the surface as [|intrusive] ([|plutonic]) rocks or on the surface as [|extrusive] rocks. This magma can be derived from partial melts of pre-existing rocks in either a [|planet]'s [|mantle] or crust

**Metamorphic rock** is the result of the transformation of an existing rock type, The study of metamorphic rocks (now exposed at the Earth's surface following erosion and uplift) provides us with very valuable information about the temperatures and pressures that occur at great depths within the Earth's crust Some examples of metamorphic rocks are [|gneiss], [|slate], [|marble], [|schist], and [|quartzite]. 
 * __Metamorphic rocks.__**