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ROCK CYCLE,
SOIL DEPOSIT
AND GRAIN-SIZE
Dr. Ir. HJ. Achmad Fauzi b Abd. WahabDr. Ir. HJ. Achmad Fauzi b Abd. Wahab
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James Hutton (17271797),
the eminent 18th century gentlemanfarmer and founder of modern
geosciences, authored the concept of therock cycle, which depicts the inter-relationships between igneous,sedimentary, and metamorphic rocks.
The Rock Cycle
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The Rock Cycle
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A rockis a naturally formed, consolidated material
usually composed of grains of one or more minerals
The rock cycle shows how one type of rocky material
gets transformed into another
Representation of how rocks are formed, broken
down, and processed in response to changingconditions
Processes may involve interactions of geosphere with
hydrosphere, atmosphere and/or biosphere
Arrows indicate possible process paths within the
cycle
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The Rock Cycle and Plate
Tectonics
Convergent plate
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(1) Igneous Rocks
Magma is molten rock
Igneous rocks form when magma
cools and solidifies
Intrusive igneous rocks form whenmagma solidifies underground
Granite is a common example
Extrusive igneous rocks form whenmagma solidifies at the Earths
surface (lava)
Basalt is a common example
Granite
Basalt
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Igneous Rocks
Texture refers to the size, shape andarrangement of grains or other constituents
within a rock
Texture of igneous rocks is primarily
controlled by cooling rate Extrusive igneous rockscool quickly at or
near Earths surface and are typically fine-
grained(most crystals 1 mm)
Fine-grained I.R
Coarse-grained I.R
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Special Igneous Rocks
Pegmatitic I.R
Porphyritic I.R
A pegmatite is an extremely coarse-grainedigneous rock (most crystals >5 cm) formed
when magma cools veryslowly at depth
A glassy texture contains no crystals at all,
and is formed by extremely rapid cooling A porphyritic texture includes two distinct
crystal sizes, with the larger having formed
first during slow cooling underground and
the small forming during more rapid coolingat the Earths surface
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Igneous Rocks Identification
Igneous rock names are based on texture (grain size) andmineralogy composition
Textural classification
Plutonic rocks (gabbro-diorite-granite) are coarse-grained and cooled
slowly at depth Volcanic rocks (basalt-andesite-rhyolite) are typically fine-grained and
cooled rapidly at the Earths surface
Compositional classification
Mafic rocks (gabbro-basalt) contain abundant dark-colored
ferromagnesian minerals
Intermediate rocks (diorite-andesite) contain roughly equal amounts of
dark- and light-colored minerals
Felsic rocks (granite-rhyolite) contain abundant light-colored minerals
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Igneous Rocks Identification
I.R.
names are
based on
texture(grain size)
&
Mineralogic
composition
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Six common Igneous Rocks
Solidifying Temperature 500 C1000 C
Increasing Grain Size
Volcanic
Rocks
Silica
Content
Minerals Present(in order of abundance)
Plutonic
Rocks
Basalt low pyroxene, olivine,feldspar, & amphibole
Gabbro
Lighter
Co
lor
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Rock types and tectonic
setting
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(2) Sedimentary Rocks
are formed bypressure, heat,and drying out.Sediments do not
necessarily haveto be undertremendouspressure to
becomesedimentary rock(as seen in the
lab).
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Sedimentary Rocks (cont)
The Earths Crust is made up of solidbedrock. (Bedrock is solid rock that isconnected continuously down into theEarths crust, rather than existing asseparate pieces or masses surrounded byloose materials
Sedimentary Rockare by far themost common rock type in theupper crust
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Sedimentary Rocks (cont)
Rocks are broken down by weathering
Sediment is transported by wind, water,or glaciers to a new site, where it is
deposited in layers. Over time, thesediments are buried and pressedtogether, or compacted.
Eventually, the sediment is cemented
together to form new rocks, know assedimentary rock.
This process takes millions of years
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Sedimentary Rockusuallylayered, that results fromthe consolidation orlithification of sediment, forexample a clastic rock likesandstone or a chemicalrock like rock salt, or an
organic rock like coal (U8). Sedimentary Rock are either
Marine (deposited in theocean) or nonmarine
(deposited on thecontinents). If marinesedimentary rock arepresent, the area must have
been below sea level.
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Sedimentary Rocks (cont)
Physical andChemicalprocesses worktogether toconvert exposedbedrock
Siliciclastic andChemical
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Sedimentary Rocks (cont)
Clastic fragments of rocks & minerals that havebeen physically transported & deposited & thenconverted into rock
Chemical Direct precipitation of minerals from asolution. Only chemical sedimentary rocks areaffected by chemical (vinegar/acid), all others arenot affected, unless the acid is strong enough.
Organic- Remains of plants and animals that have
been converted into rock
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Clastic Sedimentary Rocks
Clastic Sedimentary Rock: asedimentary rock made up ofmostly of fragments derivedfrom pre-existing rocks andtransported mechanically totheir places of deposition.
Clastic Sedimentary Rock aremade up mostly of fragments,called clasts that are erodedfrom other rocks.
Clay or Mud (Smallest 1/16 mmor smaller
Sand (1/16 to 2 mm)
Gravel (pebbles to boulders,
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Chemical Sedimentary Rocks
Rocks consist ofmaterials that haveprecipitated from theocean water or lake
water (Utah or DeathValley). Remember-Only chemicalsedimentary rocks are
affected by chemicals Precipitation: the
process of formingsolid mineral
constituents from asolution by
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Chemical Sedi. Rocks (cont)
a sedimentary rockconsisting mainly ofthe remains oforganisms (U10).
Consists of the
mineral calcite, acalcium carbonatemineral with theformula CaCO3
Organic SedimentaryRock forms whenplants in swamps withrich vegetation dieand are buried by the
remains of laterplants
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(3) Metamorphic Rocks
is rocks that have been exposed togreat heat and pressure.
A.A. Dynamic Metamorphism(RegionalDynamic Metamorphism(Regional
Metamorphism):Metamorphism):
large areas of rock are under greatheat and pressure.
Ex: mountain building.
B. ,,,,,,,
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Pressure squeezes grains closertogether, creating a denserand
less porous rock.
Heat and chemicals mayrearrange
particles (atoms). Minerals arereformed or new ones are formed.
Ex: QuartziteQuartzite was once
sandstone;sandstone;
B. How heat and pressure causerocks
to change:
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C. Characteristics of MetamorphicRocks
FoliationFoliation grains are in parallellayers. Ex: slate. Gneiss is the
coarsestfoliation of all metamorphic rocks.
BandingBanding bands of light coloredminerals alternate with bands of dark
colored minerals.
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D.Thermal Metamorphism (contactmetamorphism) Igneousintrusionsbake overlying rock.
The changes are less drastic thanregional metamorphism and foliationis not produced.
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Banding
GRANITE
GNEISS
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