Clastic sedimentary rock
Extrusive or volcanic rock
Rocks: The Rock Cycle
Metamorphic rock
Intrusive or plutonic rocks
Review: rock
forming minerals
• Silicate minerals
are formed when
a magma or lava
cools to a solid
• The solid is now
an igneous rock
Igneous intrusive or plutonic rock:
minerals are visible to the naked eye
Igneous extrusive or volcanic rock: basalt with olivine crystals;
the basalt is black because the mineral crystals are very small
Volcanic
Plutonic
Igneous rocks are formed
how?
Extrusive or
volcanic
Intrusive
or plutonic
Igneous rocks are formed
from magma crystallization.
Igneous rocks are formed
where?
Mid-oceanic ridges:
new oceanic crust
forms
Where there is a
concentration of heat
Volcanic arcs: where oceanic
crust subducts under the
opposing crust
Crystal or mineral size is
determined by cooling rate
Intrusive or plutonic
rocks are cooled within
the Earth’s crust:
cooled slowly, larger
crystals
• Extrusive or volcanic
rocks are cooled on
the Earth’s crust:
cooled quickly,
crystals smaller
Intrusive or plutonic
Extrusive or volcanic
Minerals are the building block
of rocks
Quartz
Biotitie
Feldspar crystal
Hornblende
Sketch a diagram of the rock and identify the minerals.
Igneous Textures
Large crystals “floating” in
a fine-grained matrix
Classifying igneous rocks
• Texture and mineral composition
• All terms listed on this image are important
How different compositions are
produced
The order of crystallization from basic to felsic composition based on temperature
changes.
How different compositions are
produced
•The mafic minerals
crystallize first.
•This makes the melt
more felsic
•A method of
changing the magma
composition
Sedimentary rocks
Limestone
Chemical
Biochemical
Clastic
Diatomite
Sandstone and mudstone
Chemical
Evaporate: halite and gypsum
• Water evaporates
leaving the dissolved
salts
• Calcium carbonate is
the first to form
• Gypsum is the
second
• Halite is the third
• Other salts crystallize
Halite: salt-NaCl
Gypsum: CaSO4·2H2O
• Sheet rock
• Fertilizer
Precipitates: limestone
• Precipitate from sea water
• In the same order as minerals form from
evaporation
• CaCO3 is the first and most abundant
• Limestone
Precipitation
Warm sea water becomes supersaturated in calcium
carbonate. The calcium carbonate precipitates out of
solution to form a mud. The mud hardens and becomes
limestone.
Limestone: biochemical
sedimentary rock
Formed in warm, shallow oceans
Sea water becomes
oversaturated with
calcium carbonate.
The calcium carbonate
precipitates out of
solution behind the
reef.
Limestone is used for Portland
cement
Diatomite:
biochemical
sedimentary rock
• Diatoms (single celled
plants) and mud
• Compacted and cemented
to become rock
The Monterey Formation
New Zealand
diatomite
Diatomite: biochemical
sedimentary rock
• The photic zone is the top 600 feet of the
ocean
• This is where plankton live including
diatoms
Diatomite: biochemical
sedimentary rock
Kitty Litter
Petroleum: California
Planters mix: soluble
silica; nutrient
Dynamite
Abrasive
Clastic Sedimentary Rocks
Clastic: pieces from preexisting
rock; the type of rock in exercise
Chemical or
biochemical:
we will learn
about this later
Clastic
Sedimentary
Rocks
Fragments of preexisting rocks
Clastic sediments are formed from
pre-existing rocks.
• Rocks are weathered (broken down)
Clastic sedimentary rocks
• Rocks are broken
down or weathered
Liken extracts
minerals from rock
Water extracts elements and
moves sediment
Gravity pulls broken rock down slope
Clastic sediments are formed from
pre-existing rocks.
• Eroded or moved
Wind
Water
Glaciers
Clastic sediments are formed from
pre-existing rocks.
• Deposited
Water tends to sort
sediment by size
Glaciers move
many sizes of
sediment
Stream carrying sediment into
a lake
Sediments are deposited in many
environments
Marine: beach, offshore, deep ocean
Non-marine:
glaciers, lakes,
streams,
alluvial fans
Lithification
• The sediments are buried, compacted and
cemented to become a rock.
Sandstone
What do these sedimentary
rocks have in common?
Limestone
Diatomite
Sandstone and mudstone
Sedimentary rocks are deposited in
layers.
Sand and Gravel
• Sand and gravel
is mined from
young river
deposits
• The sediment
has not been
buried or lithified.
• 1.16 billion $/yr
(CA)
Placer
Deposits
• Gold veins are exposed to the Earth’s
surface: weathered; eroded; and
deposited as sediment
• The first gold discovered in California was
a placer deposit
Metamorphic Rocks
A rock changed by heat and pressure
Metamorphic Rocks
• When rocks are
subjected to heat and
pressure, the atoms
may move around
• New minerals may
form
• Foliation or preferential
lining up of minerals,
may form
Metamorphic Rocks
• Quartzite:
recrystallized
quartz-rich
sandstone
Metamorphic
Rocks
• Foliation or
preferential lining up
of minerals, may form
Metamorphism
Metamorphic rocks
Slate: from
mudstone
Copper, zinc and
gold are
concentrated in the
bands.
Marble: from
limestone
Gneiss: from
granite
Metamorphic rocks
• Changed with heat
and pressure
• Where?
– Magma intrudes
colder rocks: colder
rocks are “baked” at
the contact
– Hot fluids from
magma: inject hot
fluid and “leftovers”
from a magma
chamber
Paired Metamorphic Belts
Subduction zone: high pressure and low temperature
metamorphic rocks
Intrusive or plutonic rocks: contact metamorphism; high
temperature, lower pressure
Metamorphic minerals are used
to determine pressure and
temperatures
Geobarometers
• Metamorphic minerals
form at distinct
temperatures and
pressures
• Therefore, geologists can
determine at what
pressures and
temperatures rocks were
formed
Geothermometers
The central Sierra Nevada were
emplaced at about 8-10 miles below
the Earth’s surface
Paired Metamorphic belts
Regional
Contact
Geobarameters:
determine pressure
The Rock Cycle
• Explains how all rocks are recycled
through different processes
• Important point: a rock’s name is
determined by how it is formed
Volcanic rock formation?
Intrusive or plutonic rock
formation?
Clastic sedimentary rock
formation?
Metamorphic rock formation?
Using the box of rocks
provided, write the steps that
would change one rock to
another rock.
What to understand:
• The process each rock must pass through
to become another rock type
• Classification of igneous, sedimentary,
and metamorphic rocks
• Where heat is concentrated to melt or
metamorphose rocks
• Metamorphic belts: where
– Geobarameters and geothermometers