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7/31/2019 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