How do the three
main types of rocks
form?
Rocks and the Rock Cycle
• How are rocks classified?
• What is the rock cycle?
Rocks and the Rock Cycle
• rock
• lava
• grain
• sediment
• texture
• rock cycle
• magma
Rocks
• A rock is a natural, solid mixture of
minerals or grains.
• Geologists call the fragments that make
up a rock grains.
• Geologists use a grain’s size, shape, and
chemical composition to classify rocks.
• Earth’s surface can cause rocks to break
apart into many different-sized fragments.
Rocks (cont.)
• The grain size and the way grains fit
together in a rock are called texture.
• When a geologist classifies a rock by
its texture, he or she looks at the size
of minerals or grains in the rock, the
arrangement of these grains, and the
overall feel of the rock.
• Texture can be used to determine the
environment in which a rock formed.
Rocks (cont.)
• The minerals or
grains in a rock
help geologists
classify its
composition.
Nancy Simmerman/Getty Images
• Composition can be used to determine
where a rock formed, such as inside a
volcano or in a river.
Rocks (cont.)
How are rocks classified?
Three Major Rock Types
• The three major groups of rocks are
igneous, sedimentary, and
metamorphic rocks.
• When magma or lava cools and
crystallizes, it creates igneous rock.
• Magma is molten or liquid rock
underground.
• Lava is magma that erupts on Earth’s
surface.
Three Major Rock Types (cont.)
• Rock fragments, mineral crystals, or the
remains of certain plants and animals,
are the building blocks of sedimentary
rocks.
• Sedimentary rocks form where sediment
is deposited.
• Sediment is rock material that forms
where rocks are broken down into
smaller pieces or dissolved in water as
rocks erode.
Three Major Rock Types (cont.)
Sediment can be deposited in
environments like rivers and streams,
deserts, and valleys.
deposit
Science Use sediment or rock
added to a landform
Common Use to put money in a
bank
Three Major Rock Types (cont.)
• Metamorphic rocks can form from any
igneous or sedimentary rock or even
another metamorphic rock.
• When rocks are exposed to extreme
temperature and pressure, such as
along plate boundaries, they can
change to metamorphic rocks.
• Chemical fluids can also cause rocks
to become metamorphic rocks.
The Rock Cycle
The series of
processes that
change one
type of rock
into another
type of rock is
called the rock
cycle.
The Rock Cycle (cont.)
• Forces on Earth’s surface and deep
within Earth drive the rock cycle.
• On the surface, rocks can change
due to natural processes, such as
weathering, erosion, deposition,
compaction, and cementation.
The Rock Cycle (cont.)
• Some rock cycle processes occur only
beneath Earth’s surface, such as those
that involve extreme temperature,
pressure, and melting.
• Uplift is a tectonic process that forces
these rocks onto Earth’s surface.
The Rock Cycle (cont.)
What is the rock cycle?
• Rocks are a natural solid mixture of
minerals or grains.
• Texture describes the size and
arrangement of minerals or grains in a
rock.
Nancy Simmerman/Getty Images
• The rock cycle represents a series of
processes that change one rock type
into another.
What do geologists call the
fragments that make up a rock?
A. minerals
B. magma
C. igneous rock
D. grains
What is rock material that forms
where rocks are broken down into
smaller pieces by water erosion?
A. lava
B. sediment
C. metamorphic rock
D. magma
When rocks are exposed to
extreme temperature and pressure
they can change into which of
these?
A. metamorphic rock
B. igneous rock
C. sedimentary rock
D. volcanic rock