Earth Science Notes

ROCK TYPES:Igneous

MetamorphicSedimentary

Igneous Rocks

Igneous Rocks Rocks that form from magma or lava

Igneous RockMagma: molten rock below the earth’s surfaceTemperature: 1202oF to 2192oFLocated about 90 miles below the surface of the

earth.Magma is less dense than the surrounding solid

rock, so it is forced to the surface.

Igneous Rock

Lava: molten rock on the surface of the earthDensity of lava effects how fluid it is.Dense lava flows very slow and has a

different chemical composition than fast moving, less dense lava.

Types of Igneous Rocks

Intrusive rocks: rocks made from magma When magma cools the molecules and

atoms in the magma begin to crystallize. These rocks cannot be seen until the rock

that is around it is worn away.Sometimes earthquakes will expose intrusive

rocks.

Intrusive Rocks

Types of Igneous Rocks

Extrusive Rocks – rocks formed from lava. Created when lava cools and hardens on

the surface Because of exposure to the air and other

elements (i.e. water) lava will cool quickly keeping crystals small.

Volcanic glass forms this way.

Extrusive Rocks

Tuff: formed from volcanic ash, pumice and scoria

Classifications of Igneous Rock

Basaltic Rocks High Density, Dark Colored,

Very Fluid Chemical Composition: Iron,

Magnesium, low silica (SiO2)

Basalt Rock Formations

Classifications of Igneous Rock Granitic Rocks

Light Colored, Low Density, Very rigid

Chemical Composition: low magnesium and Iron, high silica (SiO2)

Granitic Rock Formations

Classifications of Igneous Rock

Andesitic Rocks Intermediate between Basaltic and Granitic

IGNEOUS ROCKS

Summary Where do Igneous Rocks come from?

Magma and Lava Types of Igneous Rocks

Intrusive / Extrusive Classification of Igneous Rocks

Basaltic / Granitic / Andesitic

Metamorphic Rocks

Metamorphic Rocks Rocks that are created because of a

change in pressure and temperature.

Metamorphic Rock Formation Metamorphic rocks can form igneous,

sedimentary, or other metamorphic rocks. Pressure on these rocks can be due to the

immense amount of force applied from the rock above it.

Temperature can come from a rock being in close proximately of magma.

Classification of Metamorphic Rock

Rocks are classified according to composition and texture. Foliated rocks – formed when mineral

grains line up in parallel layers.Ex: Slate – used for blackboards, roofs,

sidewalks

Foliated rocks

Classification of Metamorphic Rock

Rocks are classified according to composition and texture. Nonfoliated rocks – metamorphic rocks where

mineral grains (crystals) grow and rearrange, but they do not form layers. Ex: Quartzite – formed from sandstone that was

changed by immense heat and pressure. Quartz crystals grow in size and become interlocking.

Ex: Marble – marble forms when limestone is put under extreme pressure and temperature.

Nonfoliated rocks

Metamorphic Rocks

Summary Metamorphic Rock Formation

Heat and pressureAny rock type can become metamorphic

ClassificationFoliated / Nonfoliated

Sedimentary Rocks

Sedimentary Rocks Rocks formed from sediments Sedimentary rocks often form as layers on

the bottom of a body of water.

Sedimentary Rock Formation Sediments are loose materials like small rocks,

minerals, and organic debris. Weathering and erosion produce sediments

Weathering – the breaking down of rocks into bits via chemical and mechanical means.

Erosion – the moving of these small bits of rock to a new location where they are deposited.

Sedimentary Rock Formation Weathering and Erosion

Sedimentary Rock Formation Sedimentary rocks form from other rocks These rocks are compacted and cemented

together. Compaction – sediments stick together due to

pressure

Cementation – minerals are deposited between pieces of sediment – holding it together.

Sedimentary Rock Formation Compaction and Cementation

Classification of Sedimentary Rocks

Detrital Sedimentary Rocks: sedimentary rocks made from broken bits of other rocks

Ex: Conglomerate – large sediments, rounded rocks These types of rocks have rounded sediments because they

were near wind and water EX: Breccia – large sediments, sediments have sharp

angles These types of rocks have jagged sediments because they

were not near wind and water

Detrital Sedimentary RocksConglomerate Breccia

Classification of Sedimentary Rocks

Chemical Sedimentary Rocks: sedimentary rocks that form when dissolved minerals come out of solution.

Often founds along seas or lakeshores. This type of rock is the only form of sedimentary

rock that did not form from preexisting rocks. Ex: Limestone (CaCO3) – forms when calcium carbonate comes out of

a solution. Limestone is deposited on bottom of lakes and seas.

Ex: Rock salt – forms when the evaporation of water occurs, leaving behind the salt

Chemical Sedimentary Rocks

Classification of Sedimentary RocksOrganic Sedimentary Rocks: sedimentary rocks made of once living things

This type of rock will form when clams, corals, snails, and mussels die and let their shells accumulate on the ocean floor. Ex: Chalk – made from the shells of organisms. Ex: Coal – formed from the decay and compaction of

plant materials.

Organic Sedimentary Rocks

Sedimentary Rocks

Summary What makes a rock

Sedimentary? Formation of Sedimentary

Rocks Classification of

Sedimentary Rocks Detrital / Chemical / Organics