Types of Rocks. 3 Basic Types Sedimentary Igneous Metamorphic.

Types of Rocks

3 Basic Types

•Sedimentary •Igneous •Metamorphic

3 Types of Sedimentary Rocks

•Clastic•Chemical•Organic

Clastic Sedimentary Rock

• Sediments form when rocks are weathered and eroded

• Sediments are moved by wind, glaciers and water

• Most clastic sediments are deposited in the ocean

Clastic Sedimentary Rock

• Particle size is key to type of rock– Gravel is > 2 mm– Sand is 1/16 mm to 2 mm– Mud is < 1/16 mm

•Clay is < 4 um•Silt is > 4 um

Sandstone

Conglomerate

Shale

Chemically Precipitated Sedimentary Rock

• Ions released during chemical weathering are carried away in solution

• Inorganic Precipitates– Halite– Gypsum

• Organic precipitates– Silica (diatoms)– Calcium carbonate – shells - CaCO3

– Dolomite - CaMg(CO3)2

Halite

Gypsum

Diatomaceous Earth

Limestone

Dolomite

Organic Sedimentary Rock

• Sediments or rocks consisting mostly or entirely from plant material– Peat– Coal

Bituminous Anthracite

Sedimentary Environments

• Lakes• Lower courses of rivers• Shallow ocean• Deep ocean

Extrusive & Intrusive Igneous Rocks

• Intrusive- Magma under the surface– Coarse-grained– Magma cools slowly and large crystals

grow over a long period of time– Gabbro, diorite, granite

Granite

Gabbro

Extrusive & Intrusive Igneous Rocks

• Extrusive- Lava at the surface– Fine-grained– Lava cools very quickly, consequently

crystals do not have time to grow and develop

– Basalt, andesite, rhyolite, obsidian

Basalt

Rhyolite

Obsidian

Explosive Volcanism

• Fragmented magma ejected explosively– Ash plumes– Pyroclastic flows

Pumice

Metamorphic Rocks

• Rocks change at the chemical level

• Grade of metamorphism• Shearing• Foliation

Nature of Metamorphism

• Changes take place while a solid• Due to heat and pressure• Protolith – original rock

Metamorphic Rocks

Foliated vs. Nonfoliated

Metamorphic Rocks

Foliated- Metamorphic rock in which minerals have been rearranged into visible bands.

Schist

Gneiss

Slate

Metamorphic Rocks

Nonfoliated- Metamorphic rock that does not show bands.

Marble

Quartzite

Regional vs. Contact Metamorphism

• Regional• Contact (or thermal)

Contact Metamorphism