Download Chapter Introduction Lesson 1 Rocks and the Rock Cycle Lesson 2

Chapter Introduction
Lesson 1 Rocks and
the Rock Cycle
Lesson 2 Igneous Rocks
Lesson 3 Sedimentary
Rocks
Chapter Wrap-Up
Steve Allen/Getty Images
Lesson 4 Metamorphic
Rocks
How do the three
main types of rocks
form?
Rocks and the Rock Cycle
•  How are rocks classified?
•  What is the rock cycle?
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.
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.
•  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.
Igneous Rocks
•  How do igneous rocks form?
•  What are the common types of
igneous rocks?
Igneous Rock Formation
•  When volcanic material erupts and cools
and crystallizes on Earth’s surface,
it forms a type of igneous rock called
extrusive rock.
•  Volcanic glass is rock that forms when
lava cools too quickly to form crystals.
•  Among the most noticeable features of
some extrusive igneous rocks are holes
that are left after gas escapes.
Igneous Rock Formation (cont.)
Igneous rocks that form as magma cools
underground are called intrusive rocks.
intrusive
from Latin intrudere, means “to
push in”
Intrusive and Extrusive Rocks
Geologists determine whether an
igneous rock is extrusive or intrusive
by studying the rock’s texture.
Igneous Rock Identification
•  If the crystals are small, the rock is
extrusive.
•  If all the crystals are large enough to
see and have an interlocking texture,
the rock is intrusive.
Igneous Rock Identification (cont.)
•  Igneous rocks are also classified, in
part, by magma composition, such as
silica content.
•  Magma composition, the location
where the lava or magma cools and
crystallizes, and the cooling rate
determine the type of igneous rock that
forms.
•  An extrusive igneous rock cools and
crystallizes from volcanic material
erupted on Earth’s surface.
•  When lava cools fast, volcanic glass
forms.
•  An intrusive
igneous rock
forms as
magma cools
and crystallizes deep inside Earth.
Sedimentary Rocks
•  How do sedimentary rocks form?
•  What are the three types of
sedimentary rocks?
Sedimentary Rock Formation
•  Mineral and rock fragments can be
transported by water, glacial ice,
gravity, or wind.
•  The sediments eventually are
deposited, or laid down, where they
can them accumulate in layers.
Sedimentary Rock Formation (cont.)
•  The weight from the layers
of sediment forces out fluids
and decreases the space
between grains during a
process called compaction.
•  Compaction can lead to a
process called cementation.
Sedimentary Rock Formation (cont.)
•  When minerals dissolved in
water crystallize between
sediment grains, the
process is called
cementation.
•  Mineral cement holds the
grains together.
Sedimentary Rock Identification
•  Sedimentary rocks that are made up of
broken pieces of minerals and rock
fragments are known as clastic rocks.
•  The broken pieces and fragments are
called clasts.
•  Sediment size alone cannot be used to
determine the environment where a
clastic rock formed.
Sedimentary Rock Identification (cont.)
•  When water becomes saturated with
dissolved minerals, particles can
crystallize out of the water and form
minerals.
•  Chemical rocks form when minerals
crystallize directly from water.
The water that once filled this lake bed
was saturated with dissolved halite. The
water evaporated and crystalline rock
salt formed.
National Geographic/Getty Images
Sedimentary Rock Identification (cont.)
•  Biochemical rock is a sedimentary
rock that was formed by organisms or
contains the remains of organisms.
•  Sometimes the remains or traces of
organisms are preserved as fossils in
biochemical rock.
Sedimentary Rock Identification (cont.)
Chemical and biochemical sedimentary
rocks are common on Earth’s surface.
•  A clastic sedimentary rock is made of
clasts of minerals or rock fragments.
•  When minerals crystallize directly from
water, a chemical sedimentary rock
results.
•  A biochemical sedimentary rock contains
the remains of living
organisms or was
formed by
organisms.
National Geographic/Getty Images
Metamorphic Rocks
•  How do metamorphic rocks form?
•  How do types of metamorphic rock
differ?
Metamorphic Rock Formation
•  Metamorphism is any process that
affects the structure or composition of
a rock in a solid state as a result of
changes in temperature, pressure, or
the addition of chemical fluids.
•  Most metamorphic rocks form deep
within Earth’s crust.
•  Like igneous rock, metamorphic rocks
form under high temperature and
pressure conditions.
Metamorphic Rock Formation (cont.)
•  Plastic deformation is the permanent
change in the shape of rock by bending
and folding.
•  Plastic deformation occurs during uplift
events when tectonic plates collide and
form mountains.
Metamorphic Rock Formation (cont.)
•  The rock that changes during
metamorphism is called the parent
rock.
•  The temperatures required to
metamorphose rock depend
on the parent rock’s composition.
Both temperature and pressure increase
with depth in Earth’s crust and mantle.
Metamorphic rocks
are classified into
two groups based
on texture:
foliated rocks and
nonfoliated rocks.
Metamorphic Rock Identification
•  Foliated rocks contain parallel layers
of flat and elongated minerals.
•  Metamorphic rocks that have mineral
grains with a random, interlocking
texture are nonfoliated rocks.
Metamorphic Rock Identification (cont.)
•  During contact metamorphism,
magma comes in contact with existing
rock, and its thermal energy and gases
interact with the surrounding rock and
forms nonfoliated metamorphic rock.
•  Regional metamorphism is the
formation of metamorphic rock bodies
that are hundreds of square kilometers
in size.
•  Foliated metamorphic rocks have
distinct layers of flat and elongated
minerals.
•  A nonfoliated metamorphic rock has
minerals arranged in a random,
interlocking texture.
•  Contact metamorphism occurs when
rocks come in contact with magma
without melting.