WHAT IS A ROCK?
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•
Any solid mass of
mineral or
mineral-like
matter that
occurs naturally
as part of our
planet
3 types
 Igneous
 Sedimentary
 Metamorphic
THE ROCK CYCLE
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•
Interactions
among Earth’s
water, air, land,
and living things
can cause rocks
to change from
one type to
another
A continuous
process
IGNEOUS ROCKS
•
Forms when lava
or magma
hardens.
•
Lava:
•
•
•
Molten rock on the
surface of the Earth
Magma:
Molten rock beneath
Earth’s surface.
IGNEOUS ROCK FORMATION
• Igneous rocks
are formed by
the cooling of
molten rocks
and the
crystallization of
minerals.
TYPES OF IGNEOUS ROCKS
•
•
Intrusive Igneous
rock: forms when
magma hardens
beneath Earth’s
surface
Extrusive Igneous
Rock: forms when
lava hardens on
the surface of the
Earth
CLASSIFYING IGNEOUS ROCKS
Igneous Rocks are
classified based
on their texture
and composition.
TEXTURE CLASSIFICATION
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•
•
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•
Texture: size, shape, and arrangement of
interlocking crystals.
Course Grained: slow cooling, large
crystals.
Fine Grained: rapid cooling, small
interconnected mineral grains.
Glassy: looks like glass, extrusive igneous
rocks. Ex. Obsidian
Porphyrite: large crystals embedded in a
matrix of much smaller crystals.
COMPOSITION CLASSIFICATION
Composition: based on proportions of light to dark
minerals
Basaltic Composition
 Contains many dark silicates minerals and plageoclase feldspar
 Rich in magnesium and iron
 Ex: basalt and gabbro
Granitic Composition
 Made almost entirely of light-colored silicate minerals like quartz
and feldspar
 0 to 25% dark minerals
 Biotite and amphibole
COMPOSITION CLASSIFICATION
Andesitic Composition
 Between basltic and
granitic composition
 At least 25% dark
minerals
Ultramafic Composition
 Composed mainly of iron
and magnesium rich
mineral
 Almost entirely dark
minerals
IGNEOUS CHART
Composition
and Texture
Granite
Andesitic
Basaltic
Ultramafic
Coarse
Granite
Diorite
Gabbro
Peridotite
Fine
Phyolite
Andesite
Basalt
Kematite
Porphyritic
Inside any given rock
Glassy
Obsidian, Pumice
Uncommon
WHAT IS A SEDIMENTARY ROCK?
Forms when existing
rocks are broken
down into
sediment then
compacted and
cemented together
Processes
 Cementing
 Compaction
HOW DO THEY FORM?
 Weathering: Any process that
break rocks into sediments
 Erosion : The removal of
weathered rocks
 Deposition: when an agent of
erosion (water, wind, ice, or
gravity) loses energy, it drops
the sediment
 Compaction: is a process that
squeezes or compacts
sediments together
 Cementation: takes place
when dissolved minerals are
deposited in the tiny spaces
among the sediments
CLASSIFICATION OF SEDIMENTARY ROCKS
• Classified by the
way they form
•
Clastic or chemical
CLASTIC SEDIMENTARY ROCKS
• Made of
weathered bits
of rocks and
minerals
• Grouped
according to the
size of the
sediment.
CLASTIC SEDIMENTARY ROCKS
Texture
Sediments
Name of Rock
Coarse
Gravel - rounded Conglomerate
(over 2 mm in
size)
Gravel- angular
Breccia
Medium (2mm
Sand
Sandstone
Silt
Siltstone
to 1/6 mm)
Fine (1/16 to
1/256 mm)
Very Fine
1/256 mm)
(< Mud
Shale/mudstone
CHEMICAL SEDIMENTARY ROCKS
Form when dissolved
minerals precipitate
from water solution
Biochemical
Sedimentary Rock:
made from once living
organisms (like shells
and skeleton remains)
 Ex: limestone, chalk,
conquina, rock salt, and
bituminous coal
WHAT IS A METAMORPHIC ROCK?
Form when existing
rocks are
changed by heat
and pressure
Metamorphism:
means “change
form”
WHAT CAUSES METAMORPHISM?
Heat: provides the energy needed to drive chemical
reactions which causes existing minerals to
recrystallize
Pressure: applied in all directions on a rock which
causes spaces between mineral grains to close
Hydrothermal Solutions: hot, water based solutions
that promote recrystallization by dissolving original
minerals and then depositing new ones
CLASSIFICATION OF METAMORPHIC ROCKS
Classified by texture and
composition
Foliated
 Rock with layered or banded
appearance
 Ex: Gneiss
Nonfoliated
 No layered or banded appearance
 Contains only one mineral
 Ex: Marble
CLASSIFICATION OF FOLIATED METAMORPHIC
ROCKS
Name
Texture/Grain Size
Parent Rock
Slate
Very fine
Shale, mudstone
Phyllite
Fine
Slate
Schist
Medium to course
Phyllite
Gneiss
Coarse
Schist, granite
CLASSIFICATION OF NON-FOLIATED
METAMORPHIC ROCKS
Name
Texture/grain size
Parent rock
Marble
Medium to coarse
Limestone
Quartzite
Medium to coarse
Quartz, sandstone
Anthracite
Fine
Coal