Earth Science- Rocks Study Guide
3 Major Types of Rocks
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Igneous Rock- magma or molten rock cools and hardens.
Sedimentary Rock- sediment deposits form when rocks, mineral crystals and organic
matter have been broken into fragments are composed and cemented together.
Metamorphic Rock- forms when existing rock is altered by changes in temperature
and/or pressure or chemical processes.
Rock Cycle
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Any three rocks can be changed into another of the three types
Geologic forces cause rock to change from one type to another.
Geological processes is which rocks form and changes from one to another. It’s
destroyed and formed again.
Properties of Rocks
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To know where and how the rocks were formed you must look at the physical and
chemical properties.
Chemical stabilities of minerals in rocks – the rate at which rock weathers and the
way it breaks apart.
Bowen’s reaction series- the order in which minerals crystallize from cooling magma
according to their chemical composition and melting point.
Chemical Stability
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The pattern of mineral formation from magma
The rate at which mineral chemically breaks down
A measure of the chemical compound to maintain its original chemical composition
Dependent on the strength of the chemical bonds between atoms in the mineral
Physical Stability
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Natural zones of weakness that are determined by how and where the rock forms
Rocks formed under intense pressure are uplifted to Earth’s surface then decreased
pressure allows the joints or fractures to open.
The process of chemical and mechanical weathering can begin once the weaknesses
are exposed to air and water.
Igneous Rocks
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Igneous rocks- rock that forms when magma cools and solidifies.
3 factors that affect whether rocks melt
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Temperature- when temperature of rock increases to above the melting point of
minerals in rock
Pressure- when excess pressure is removed from rock that is hotter than its melting
point
Presence of fluids in the rock- when fluids such as water are added. The addition of
fluids generally decreases the melting point of certain minerals in the rock
Partial Melting
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Minerals that have lower melting points are the first to melt
As temperature increases and other minerals melt the magma’s composition
changes
Process which different minerals melt at different temperatures
Fractional Crystallization
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Crystallization and removal of different minerals from the cooling magma
When magma cools the process is the reverse of the process of partial melting
Minerals that have the highest freezing point crystallize first
Felsic Rock- light in color
Mafic Rock- dark in color
Intermediate Rock- medium in color
Batholiths, Laccoliths, Sills and Dykes- Label the diagram
Metamorphic Rocks
Metamorphism- process in which one type of rock changes into metamorphic rock because of
the chemical processes or changes in the temperature or pressure.
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Heat, pressure and hot fluids cause change
Size and shape gives rocks a layered appearance
Two types of metamorphism
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Contact metamorphism- a change in texture, structure or chemical composition of a
rock due to contact with magma
Regional metamorphism- a change in texture, structure or chemical composition of
a rock due to changes in temperature and pressure over a large area, generally are a
result of tectonic forces
Sedimentary Rocks- made up of different types of sediment
Two main processes convert loose sediment into sedimentary rock:
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Compaction- volume and porosity of a sediment is decreased by the weight of
overlying sediments as a result of burial beneath other sediments
Cementation- minerals precipitate into pore spaces between sediment grains and
bind sediments together to form rock
Three main classes of sedimentary rock:
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Chemical Sedimentary Rocks- rocks that form when minerals precipitate from a
solution or settle from suspension. Give one example: Gypsum
Organic Sedimentary Rocks- rock that forms from the remains of plants or animals.
Give on example: Coal
Clastic Sedimentary Rocks- rock that forms when fragments of preexisting rocks are
compacted and cemented together. Give on example: Shale
Rock Features- This section will be matching
Stratification- layering of sedimentary rocks
Cross-beds or slanting layers- commonly form in sand dunes or river beds
Graded bedding- various sizes and kinds of materials are deposited in one layer, with the
largest grains at the bottom and the finest grains at the top
Ripple marks- form when air or water flows over sand to form ripples and the ripples are
preserved in the rock. Form at a beach or on a river bed
Mud cracks- form when muddy deposits form and shrink. The shrinking causes the drying mud
to crack.
Fossils- the remains of organisms that are preserved in rock
Concretions- lumps of minerals that precipitate from fluids and build up around a nucleus or in
a cavity in existing rock