Download Sedimentary Rocks

Rocks and Minerals/Rock Cycle Notes
How are rocks
classified?
What are the
two categories
of igneous
rocks?
Which
category would
have minerals
with larger
crystals?
How Rocks are Classified
Rocks are classified by the process by which they are formed: igneous (of
fire) from cooling magma or lava, sedimentary from cementation and
compaction of weathered rock (sediment), and metamorphic rock from the
pressure and heat applied to any type of rock, causing it to change.
Igneous Rocks
Extrusive (Volcanic)
Type of Magma/Lava Intrusive (Plutonic)
Solidify within Earth
Erupted on Surface
Basaltic
ex. Gabbro
ex.'s: Basalt
Scoria
Andesitic
ex. Diorite
ex. Andesite
ex. Granite
ex.'s: Rhyolite
Pumice
Obsidian
Rhyolitic / Granitic
Large Grain Size -- Slow cooling
Small Grain Size -- Rapid cooling
Sedimentary Rocks
Pieces of rock are loosened by weathering, then transported to some
basin or depression where sediment is trapped. If the sediment is
buried deeply, it becomes compacted and cemented, forming
sedimentary rock.
Sedimentary rocks are classified two ways: clastic and non-clastic,
What are the
two categories
of sedimentary
rocks?
which are classified as biologic, or chemical.
Clastic sedimentary rock
Clastic sedimentary rocks are made up of pieces (clasts) of preexisting rocks. Clastic sedimentary rocks may have particles ranging in
size from microscopic clay to huge boulders. Their names are based on
their clast or grain size. The smallest grains are called clay, then silt,
then sand. Grains larger that 2 millimeters are called pebbles. Shale is a
rock made mostly of clay, siltstone is made up of silt-sized grains,
sandstone is made of sand-sized clasts, and conglomerate is made of
pebbles surrounded by a matrix of sand or mud.
Non-Clastic Sedimentary rock
What are the
two subcategories of
non-clastic
rocks?
Biologic sedimentary rock
Biologic sedimentary rocks form when large numbers of living things
die, pile up, and are compressed and cemented to form rock.
Accumulated carbon-rich plant material may form coal. Deposits made
mostly of animal shells may form limestone, coquina, or chert.
Chemical sedimentary rock
What are the
two processes
which create
sedimentary
rocks?
Chemical sedimentary rocks are formed by chemical precipitation. The
stalactites and stalagmites you see in caves form this way, so does the
rock salt that table salt comes from. This process begins when water
traveling through rock dissolves some of the minerals, carrying them
away from their source. Eventually these minerals can be re-deposited,
or precipitated, when the water evaporates away or when the water
becomes over-saturated with minerals.
Metamorphic Rocks
All other rocks can be changed into metamorphic rock with heat and
pressure. The heat can come from the core, radioactive decay, or close
contact with molten materials.
Foliated metamorphic rock
What are the
two categories
of
metamorphic
rocks?
Foliation forms when pressure squeezes the flat or elongate minerals
within a rock so they become aligned. These rocks develop a platy or
sheet-like structure that reflects the direction that pressure was
applied in. Slate, schist, and gneiss (pronounced 'nice') are all foliated
metamorphic rocks.
How could you
see the
difference
between these
categories?
What two
processes
create
metamorphic
rocks? What
causes these
two
processes?
Non-foliated metamorphic rock
Non-foliated metamorphic rocks do not have a platy or sheet-like
structure. No matter how much pressure you apply, the grains will not
align!
ROCK NAME
TYPE
PARENT
ROCK
CHARACTERISTICS
SLATE
foliated
shales and
muds
prominent splitting surfaces; crystals not
visible
SCHIST
foliated
fine grained
rocks
mica-type minerals visible, often including
larger crystals of other metamorphic
minerals such as garnet; foliation often
crinkled or wavy
GNEISS
foliated
coarse
grained
granite
dark and light bands or layers of
ferromagnesian and non-ferromagnesian
silicate minerals
sandstone
interlocking almost fused quartz grains,
little or no porosity
limestone
interlocking, often coarse, calcite or
dolomite crystals, little or no porosity
QUARTZITE non-foliated
MARBLE
non-foliated
The Rock Cycle
What are the
“parent” rocks
of gneiss and
marble?
The rock cycle is a way of looking at how any rock is able to be changed
into any other type of rock.
Summaries