Rocks: Mineral Mixtures

Rocks: Mineral Mixtures

Chapter 4

Rock DefinitionRock Definition

Solid mixture of one or more minerals

Rock CycleRock Cycle

Process in which one rock type changes into another rock type

Three Rock types:IgneousSedimentaryMetamorphic

Weathering and Erosion– Forms clasts or grains

DepositionCompacting and Cementing

– Glues rock together, usually in layers

Rock Cycle Mechanics: SedimentaryRock Cycle Mechanics: Sedimentary

Metamorphism MechanicsMetamorphism Mechanics

MetamorphismRock undergoes Heat and Pressure

Igneous MechanicsIgneous Mechanics

MeltingMagma under crustLava on Earth’s surface

Cooling Solidification

Rock ClassificationRock Classification

Color Composition

Minerals determine make-up of the rock Texture

Size and shape of grains– Fine– Medium – Coarse

Igneous RocksIgneous Rocks Rock formed from cooling magma or lava Three ways rock can melt:

Increase in temperatureRelease of pressureComposition

– Fluids and gases can lower melting point of rock Rocks will freeze between 700 and 1,250

Water freezes at 0 degrees Celsius Comes from Latin word for “fire”

CompositionComposition

FelsicLightweightLight in colorHigh silica

MaficDark in colorDense or heavyLow silica

TextureTextureIntrusive

Coarse grainedCools below crustCools slowly

ExtrusiveFine grainedCools above the crustCools quickly

Composition and TextureComposition and TextureCoarse-Grained Fine-Grained

Felsic:High silica

Granite Rhyolite

Mafic:Low silica

Gabbro Basalt

Igneous StructuresIgneous Structures

Volcanic necks Pluton and Batholith Lava flows and sills

Sedimentary rocksSedimentary rocks Rock that is formed when sediments are

compacted and cemented together Dissolved minerals in solution glue sediments

together Forms at or near the Earth’s surface Sediment rocks form in layers known as strata

Sedimentary RocksSedimentary Rocks

Composition of Sedimentary rocks

Composition of Sedimentary rocks

Classified by way it forms Classifications:

ClasticChemicalOrganic

Clastic SedimentaryClastic Sedimentary

Made of fragments of other rocks Grain size helps identify rock

Coarse = ConglomerateMedium = Sand/siltstoneFine = Shale

Chemical SedimentaryChemical Sedimentary

Forms from solutions of minerals and water Precipitation dissolves minerals Rock forms through evaporation, or will

crystallize out of water solution

Organic SedimentaryOrganic Sedimentary

Comprised of the remains of once living organisms

Some limestone is formed this way Comprised of Calcium Carbonate

Reacts with acid

Sedimentary Rock StructureSedimentary Rock Structure

StratificationLayering of sedimentary rock

Layers are called Strata

Metamorphic RocksMetamorphic Rocks Meta = Changed Morphos = Shape Rock that forms when composition and texture of

preexisting rock is changed by heat and pressure Enlargement and rearrangement of grains Change occurs deep underground (plate tectonics) Two Common Types

Regional Contact

Metamorphism TypesMetamorphism Types Contact Rock does not melt, but

cooks into new rock

Regional Enormous pressure Due to crust colliding Found near continental

formations (mountains)

CompositionComposition

Conditions allow for minerals to combine making new rocks

Some minerals will only form at certain pressure and heat ranges

TextureTexture Foliated Mineral grains aligned

due to pressure

Nonfoliated Lacks mineral alignment Commonly made of one

or a few minerals