Earth Science - Rocks

Sedimentary and Metamorphic rocks

пЃ® Rocks formed when sediments are cemented or compacted once these sediments are deposited.

пЃ® Constitutes about 5% of the Earths crust.

пЃ® Many of these rocks also contain fossils.

пЃ® Many of these rocks are important economically. (Energy resources)

Classification of sedimentary rocks

пЃ® Can be classified as 1) detrital and 2) chemical

пЃ® 1.Detrital: Rocks formed mostly by mechanical weathering

пЃ® Grouped based on particle size:

-Coarse (Ex . Conglomerate, breccia)

-Medium (ex. Sandstone)

-Fine (Ex. Siltstone)

-Very Fine (Ex. Shale

пЃ® 2. Sedimentary rock that is formed from chemical sediments, which are precipitated from solution.

пЃ® Formed from chemical weathering

пЃ® EX. Limestone, travertine, coal, coquina, rock gypsum, rock salt.

Metamorphic rocks

пЃ® Rocks formed from metamorphism (transformation of one rock to another)

пЃ® Metamorphism occurs when preexisting rock is subjected to temperatures and pressures unlike those in which it is formed.

Metamorphism

пЃ® Slight changes low grade metamorphism) to Substantial changes ( high grade )

пЃ® Shale turns into slate with heat and pressure.

пЃ® 2 setting of metamorphism

пЃ® 1)thermal ( contact)- rock is exposed to magma

пЃ® 2)Regional-tocks are exposed to high temperature pressure (mountain , building)

Agents in Metamorphism

пЃ® Heat

пЃ® Pressure stress)

пЃ® Chemically active fluids( water vapor , carbon oxide)

Metamorphic Texture

пЃ® Foliated- consists of layers (slate , schist and gneiss)

пЃ® Non-Foliated-Lacks layers ( anthesite , marble

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