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Sedimentary Rocks
Formation of Sedimentary Rocks
Sedimentary rock forms
at or near the surface,
when sediments are
pressed and cemented
together, or when
minerals form from
solutions.
 Sedimentary rocks often
form as layers, strata.
 The process by which
sediment becomes
sedimentary rock is
known as lithification.
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What is sediment?
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Sediments are loose
materials such as rock
fragments, mineral
grains, and remains of
some organisms caused
from
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Sediments come from weathered and
eroded igneous, metamorphic, and
sedimentary rocks.
Classifying Sedimentary Rocks
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Sedimentary rocks are classified by their
composition and by the manner in which
they formed.
The three types of sedimentary rocks
are:
– Clastic
– Chemical
– Organic
Clastic Sedimentary Rocks
Clastic sedimentary rocks are made
from the broken fragments of other
rocks cemented together by a
mineral.
 Clastic sedimentary rocks can have
coarse-grained, medium-grained, or
fine-grained textures
 Ex. Sandstone, breccia, conglomerate,
shale

Shale = forms from
the compaction of
silt and clay-size
mineral particles
Sandstone = formed where sand is laid and
buried – beaches, dunes, and seafloors
Monument Valley in Arizona
Clastic Sedimentary Rock
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Processes that help form sedimentary rocks:
Weathering = Breaking down of material by
wind, water, ice, sunlight, & gravity
Erosion = Movement of sediments
Deposition = The process by which sediment
is dropped or settles in new locations.
Compacted = Smaller sediments pushed
together
Cemented = Dissolved minerals such as
quartz or calcite act as a natural glue
cementing larger sediments together
Chemical Sedimentary Rocks
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Chemical sedimentary rocks form from solutions
of dissolved minerals and water.
Minerals crystallizes out of solution
Ex. Halite, limestone, gypsum
Organic Sedimentary Rock
• Rocks made of the remains of once-living
things are called organic sedimentary rocks.
• One of the most common organic
sedimentary rocks is fossil-rich limestone.
• Coal- forms
underground from plant
material buried under
sediment & changed to
coal over millions of
years
Example of Organic
Sedimentary Rock
• Chalk is another
organic sedimentary
rock that is made of
microscopic shells.
• When you write with
naturally occurring
chalk, you’re crushing
and smearing the calcite-shell remains
of once-living ocean organisms.
forms when sediments are
pressed and cemented
together, or when minerals
form from solutions
already-existing
rocks that are
weathered and
eroded
Clastic
compaction
Broken
fragments of
other rocks
cementation
Chemical
Dissolved minerals come out
of solution
limestone
weathering
erosion
Halite
Organic
Made of the
remains of once
living things
chalk
coal