Modul 6 - Rocks

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    RocksRocks

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    RocksRocks

    What is a rock?What is a rock?

    A rock is a naturally formed aggregateA rock is a naturally formed aggregate

    composed of one or more mineralscomposed of one or more minerals

    Rocks are aggregates of one or moreRocks are aggregates of one or moremineralsminerals

    Which one is the best answer?Which one is the best answer?

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    RocksRocks

    Example of a rock, an aggregate of more than one mineralsExample of a rock, an aggregate of more than one minerals

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    RocksRocks

    Rocks are classified on the basis ofRocks are classified on the basis of

    how they formhow they form

    There areThere are 3 major classes3 major classes of rocks:of rocks:

    Igneous rocksIgneous rocks

    Sedimentary rocksSedimentary rocks

    Metamorphic rocksMetamorphic rocks

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    Igneous RocksIgneous Rocks

    Igneous Rocks form by crystallization of moltenIgneous Rocks form by crystallization of molten

    rock materialrock material

    Molten rock material below EarthMolten rock material below Earths surface iss surface is

    calledcalled magmamagma

    Molten rock material erupted above EarthMolten rock material erupted above Earthss

    surface is calledsurface is called lavalava

    The name changes because the compositionThe name changes because the compositionof the molten material changes as it is eruptedof the molten material changes as it is erupted

    due to escape of volatile gasesdue to escape of volatile gases

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    Metamorphic RocksMetamorphic Rocks

    Metamorphic rocks are changed rocksMetamorphic rocks are changed rocks

    They areThey are formed in the solid stateformed in the solid stateininresponse to one or more of theresponse to one or more of the

    followingfollowing agents of metamorphismagents of metamorphism::

    Change inChange in pressurepressure

    Change inChange in temperaturetemperature

    Change inChange in pressurepressureandand temperaturetemperature

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    Metamorphic RocksMetamorphic Rocks

    TheThe protolithprotolith(the(the parent rockparent rock) is the) is thepreexisting rock from which thepreexisting rock from which the

    metamorphic rock was formedmetamorphic rock was formed

    Metamorphism may cause a change in aMetamorphism may cause a change in a

    rockrocks:s: CompositionComposition

    Mineral assemblageMineral assemblage TextureTexture

    All of the aboveAll of the above

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    Sedimentary RocksSedimentary Rocks

    Rocks formed from material derived fromRocks formed from material derived from

    preexisting rocks bypreexisting rocks by surfacialsurfacial processesprocesses

    followed byfollowed by diagenesisdiagenesis There are two main classes of sedimentaryThere are two main classes of sedimentary

    rocksrocks

    ClasticClastic((detritaldetrital) sedimentary rocks) sedimentary rocks

    Chemical sedimentary rocksChemical sedimentary rocks

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    Sedimentary RocksSedimentary Rocks

    ClasticClasticsedimentary rockssedimentary rocksare formed fromare formed frombits and pieces of previously existingbits and pieces of previously existing

    rocks, called clasts or detritusrocks, called clasts or detritus

    Chemical sedimentary rocksChemical sedimentary rocksare formed inare formed in

    several waysseveral ways

    By precipitation from aqueous solutionBy precipitation from aqueous solution

    From plant materialFrom plant material

    From animal materialFrom animal material

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    Sedimentary RocksSedimentary Rocks

    Processes Leading to Formation ofProcesses Leading to Formation of

    Clastic Sedimentary RocksClastic Sedimentary Rocks

    Weathering:Weathering: the processes that change rocksthe processes that change rocks size andsize and

    composition at or near Earthcomposition at or near Earths surfaces surface

    Erosion and Transportation:Erosion and Transportation: removal of rock particlesremoval of rock particles

    (clasts) from their source by water, wind, or glacial ice(clasts) from their source by water, wind, or glacial ice

    Deposition:Deposition: the settling of clasts on Earththe settling of clasts on Earths surface ass surface assediments, leads to formation of a sedimentary bedsediments, leads to formation of a sedimentary bed

    Compaction:Compaction: pressing together of clasts, squeezing outpressing together of clasts, squeezing out

    pore water, by pressure exerted by overlying bedspore water, by pressure exerted by overlying beds

    LithificationLithification:: cementation of clasts together to form acementation of clasts together to form a

    sedimentary rocksedimentary rock

    DiagenesisDiagenesis::a process of conversion of unconsolidateda process of conversion of unconsolidatedsediments to coherent sedimentary rockssediments to coherent sedimentary rocks

    R k C lR k C l

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    Rocks CycleRocks Cycle

    R kR k

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    RocksRocks

    How can you identify rocksHow can you identify rocks megamega

    ColorColor:: the first guide to differentiatethe first guide to differentiateminerals, texture, and structureminerals, texture, and structure

    Mineral compositionMineral composition::names (with briefnames (with brief

    description) and percentage of individualdescription) and percentage of individualmineralmineral

    TextureTexture::the relationship between thethe relationship between the

    grains of minerals forming a rockgrains of minerals forming a rock StructureStructure::the relationship betweenthe relationship between

    different parts of a rockdifferent parts of a rock