Chapter 6.1
Formation of Sedimentary Rocks
Vocabulary
• Texture- the size, shape, and crystal size
• Sediment- Pieces of solid material that have
been deposited on Earth’s surface by wind,
water, ice, gravity, or chemical precipitation.
• Lithification- physical and chemical process
that transform sediments into sedimentary
rocks.
Vocabulary Cont.
• Cementation-when mineral growth cements
sediment grains together into rock.
• Cross-bedding- bedding in which the particle
sizes become progressively heavier and coarser
towards the bottom layers.
• Graded bedding- bedding formed when inclined
layers of sediment move forward across
horizontal surface.
• Bedding- horizontal layering of sedimentary
rocks.
Weathering
Weathering
Occurs when
Earth’s crust
is exposed
Produces clastic
sediment
Physical
Processes
Minerals in
rock are
chemically
unchanged.
Rock fragments
break off.
Occurs through
Chemical
Processes
Minerals in
rocks are
chemically
changed.
Erosion and Transport
Wind
Gravity
Moving Water
Glaciers
Process of Lithification
• Lithification begins when the weight
of overlaying sediments forces
sediment grains closer together.
Water in pressed out. The grains are
then compacted together.
Sediments that are buried will
experience high temperatures and
will have cementation.
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Section 6.2 Vocab
Clastic: sediments having particles ranging in size
from boulders to microscopic particles, which
often have worn surfaces and rounded corners.
Clastic Sedimentary Rock: sedimentary rocks
formed from deposits of loose sediments
Porosity: the percentage of open spaces
between grains in a rock
Evaporite: chemical sedimentary rocks that form
as a result of crystal grains precipitating out of a
supersaturated body of water
Reservoir: a subsurface area of rock that has
enough porosity to allow for the accumulation
of oil, natural gas, or water
Clastic sedimentary rocks
Coarse-grained
Type of fragments: gravel size
Types of rock formed: conglomerate, breccia
Formed by: high-energy flows of water
Medium Grained
Type of fragments: sand
Type of rock formed: sandstone
Formed by: stream and river channels, beaches, deserts
Fine-grained
Type of fragments: silt and mud
Type of Rock formed: siltstone, shale
Chemical Sedimentary Rocks
Medium-grained clastics
Porosities as high as 30-40%
-When pore spaces connected it allows for water
to move through sandstone
Can hold reservoirs of oil, natural gas, and
groundwater
Fine-grained clastics
Very low porosity
Form barrier to the movement of groundwater
and oil
Chemical Sedimentary Rocks
Sequence
6 Thick layers of evaporites can accumulate as
___
evaporation removes freshwater.
2 Water evaporates and leaves behind dissolved
___
minerals.
1 Minerals are dissolved and carried into lakes and
___
oceans by chemical weathering.
5 Layers of chemical sedimentary rocks called
___
evaporites form.
3 The concentration of minerals reaches the
___
saturation point.
4 Crystal grains precipitate out of the solution and
___
settle on the bottom.
Biochemical Sedimentary Rocks
What forms them
The remains of the
once-living animals and
plants
Where they form
Shallow-water
environments Swamps and
coastal areas
How limestone forms
Organisms use calcium
carbonate in seawater to
make their shells. Calcium
carbonate precipitates out
of the water and crystallizes
between the grains of
calcium sediment during
lithification.
How Coal forms
Thick layers of vegetation
accumulate. The layers are
buried and compressed and
are lithified into coal.
Importance of Sedimentary Rocks
Provide
Information
about
Past
Animals and
plants
Sedimentary
Rocks
Provide
Resources
Uranium
Phosphate
And iron
Oil, natural
Gas, and coal
Building
materials
Bedrock
Ancient
Rivers, lakes,
And shorelines
Real-World Connection
A company want to drill a new oil well. They know that a layer
of oil containing shale is located beneath a thick layer of
siltstone. Describe challenges the company might face.
The siltstone has low porosity, so the oil will not flow
though it. The company would have to drill though the
siltstone to reach the oil-containing shale. If the layer
of siltstone is too thick, the company might not be able
to drill deep enough to reach the oil.
6.3 Metamorphic
Rocks
Intrusive- Igneous rocks that cool slowly beneath
Earth’s surface
Regional Metamorphism- Belts of metamorphic rock
covering large areas
Contact Metamorphism- Metamorphism that occurs
when molten rocks come in contact with solid rocks.
Hydrothermal Metamorphism- Metamorphism
caused when very hot water reacts with rocks and
alters its chemistry and mineralogy.
Foliated- Metamorphic rocks containing wavy layers
and bands of minerals.
Nonfoliated- Metamorphic rocks composed of
minerals with blocky shapes.
Rock Cycle- The continuous cycle of changing and
remaking rocks.
Causes of Metamorphism
Conditions necessary for metamorphism
High Pressure
Low Pressure
Can be caused by
1. Materials being
buried alive
2. Igneous intrusion
1. Weight of the rocks above
2. Compressive forces
during mountain building
Types of Metamorphism
I. Regional Metamorphism
A. Occurs when high temperatures and pressure affect large
regions of Earth’s crust.
B. Geologists can divide metamorphic rock belts into zones
based on the mineral groups found in the rocks.
II. Contact Metamorphism
A. Occurs when magma comes in contact with solid rock.
B. Can result in zones of different mineral surrounding an
intrusion.
III. Hydrothermal Metamorphism
A. Occurs when very hot water reacts with rock and changes
its chemistry and mineralogy.
B. Can result in dissolved minerals, break down of minerals,
and deposits of new minerals.
Metamorphic Texture
Texture
Shape of
crystals
How formed
Foliated
Flat,
High pressure
needlelike during
metamorphism
Schist, gneiss
Nonfoliated
blocky
Quartzite,
marble
Porphyroblast
Very large Reorganization of garnet
atoms during
metamorphism
No pressure
during
metamorphism
Examples
Mineral Changes
Compare mineral changes in metamorphism to changes
in fractional crystallization. Name the process of
mineral change in metamorphism.
Like in fractional crystallization. Minerals in
solid rock are stable at certain temperatures
and pressures. During metamorphism. The
minerals in rock change into new minerals.
The new minerals are stable under the new
temperatures and pressure conditions.
These kinds of changes are called solidstate alterations.
Composition Changes
Hot fluid movie in and out of rock
during metamorphism. This can change
the original composition of the rock.
Chemical changes often happen during
contact metamorphism near igneous
intrusions. Hydrothermal fluids move
into the surrounding rocks and change
their mineralogy, texture and chemistry.
Synthesize
A geologist says that a certain rock us 500 million
years old. Tell if this can be true, and why or why
not.
Rocks are constantly changing from one
type through internal and external
processes. A rock’s age tells when it
took its present form.
Other
 Metamorphic is Latin of “Changed form”
 James Hutton proposed the rock cycle in the
1700’s