Structure of the Earth
Have you ever wondered how Earth is put together? Most people live their lives every
day. They don’t think about what is under their feet. Some people wonder about Earth.
They think about Earth. They explore Earth. They are geologists. They study Earth.
They study its structure. They have learned many things.
crust
mantle
outer
core
inner
core
For Eggsample...
Think of Earth as a hard-boiled egg. An egg has a shell. Earth has a crust. An egg
has liquid under its shell. Earth has hot magma under its crust. The Earth is much
bigger than an egg. It is 6,400 kilometers (4,000 miles) from its crust down to its center!
We live on Earth’s crust. The crust is the part of Earth that has cooled and hardened.
There are seven continents on Earth. They are all a part of the crust. The ocean floor is
also a part of the crust. Mountains rise up from the crust.
An eggshell can get a crack. Our crust is cracked. Look at the edges of the
continents. You might notice that they look like cracks on an eggshell.
Earth also has other layers under the crust. The first layer is the mantle. Then comes
the core. There is an outer core. Then there is an inner core. These layers are made
of magma, or molten rock. The heat there can go up to hundreds and thousands of
degrees.
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© Shell Education
#50160—Leveled Texts for Science: Earth & Space Science
Recycling Crust
Magma comes to the surface. It comes through cracks in Earth’s crust. This makes
new crust. Does that mean there is more crust now than in the past? That doesn’t
make sense. Geologists have worked hard to find out how it works.
Earth oozes magma in one place. It makes new crust there. For this to happen it
must destroy crust some other place. Geologists looked for that place. They found how
it works. New crust is made in the Atlantic Ocean. It is destroyed in the Pacific. The
Atlantic Ocean floor expands with new crust. The Pacific Ocean floor shrinks.
Geologists found out how. The Pacific Ocean floor dives down. It goes into deep
trenches. These are called subduction zones. The crust in the ocean floors shows how
Earth recycles. Rocks are created. Later they
are melted again. Proof of this comes from
maps. The maps show where there have been
earthquakes. They show where there are
volcanoes. The maps show undersea ridges
and subduction zones.
Comprehension Question
Name the layers of Earth.
46
#50160—Leveled Texts for Science: Earth & Space Science
© Shell Education
Structure of the Earth
Have you ever wondered how Earth is put together? Most people live their lives every
day without thinking about the planet under their feet. Some people do. They wonder
about Earth. They think about it. They explore it. These people are geologists. They
study Earth and its structure. They have discovered many things.
crust
mantle
outer
core
inner
core
For Eggsample...
Think of Earth as a hard-boiled egg. An egg has a shell. Earth has a crust. An egg
has liquid under its shell. Earth has hot magma under its crust. The Earth is much
bigger than an egg. It is 6,400 kilometers (4,000 miles) from its crust down to its center!
We live on Earth’s crust. The crust is the part of Earth that has cooled and become
hard. All of the continents of Earth are a part of the crust. The ocean floor is also a
part of the crust. Mountains rise up from the crust.
Just like an eggshell with a crack, our crust is cracked. Look at the edges of the
continents. You might notice that they look like cracks on an eggshell.
Earth also has other layers beneath the crust. The first layer is the mantle. Then
come the outer and inner cores. These layers are made of magma, or molten rock. Their
temperatures range from hundreds to thousands of degrees Fahrenheit.
47
© Shell Education
#50160—Leveled Texts for Science: Earth & Space Science
Recycling Crust
Molten magma rises to the surface through cracks in Earth’s crust. This makes
new crust. Does that mean there is more crust on the surface of Earth now than in the
past? That doesn’t make sense. Geologists had a theory to explain what happens.
Earth oozes magma in one place. It makes new crust there. It must destroy crust
somewhere else. Sure enough, studies found how it works. New crust is made in
the Atlantic Ocean, and is destroyed in the Pacific Ocean. The Atlantic Ocean floor
expands with new crust. The Pacific Ocean floor shrinks.
Geologists found out how. The Pacific Ocean floor dives down. It goes into deep
trenches under continents. These trenches are called subduction zones. The crust
in the ocean floors is an example of how Earth recycles. Rocks are created and later
melted again. Proof of this comes from
mapping earthquakes and volcanoes. Most
of them are found near undersea ridges and
subduction zones.
Comprehension Question
Describe the layers of Earth.
48
#50160—Leveled Texts for Science: Earth & Space Science
© Shell Education
Structure of the Earth
Have you ever wondered how Earth is put together? Most people live their lives every
day without thinking about the planet under their feet. Some people do: they wonder
about Earth; they investigate it, they theorize about it, and they explore it. These people
are geologists, and they study the Earth and how it is structured. They have discovered a
number of interesting things.
crust
mantle
outer
core
inner
core
For Eggsample...
Imagine Earth as a hard-boiled egg. An egg has a shell. Earth has a crust. An egg
has liquid under its shell. Earth has hot magma under its crust. If Earth were an egg, it
would be a 6,400-kilometer (4,000-mile) trip from its shell (the crust) down to its center!
We live on Earth’s crust. The crust is the part of Earth that has cooled and hardened.
All of the continents of Earth are a part of the crust. The ocean floor is also a part of
the crust. Mountains rise up from the crust.
Just like an eggshell with a crack, our crust is cracked. If you look at the edges of the
continents, you might notice that they look like cracks on an eggshell.
Earth also has other layers beneath the crust. They are the mantle and the outer and
inner cores. These layers are made of magma, or molten rock, and their temperatures
range from hundreds to thousands of degrees Fahrenheit.
49
© Shell Education
#50160—Leveled Texts for Science: Earth & Space Science
Recycling Crust
Molten magma rises to the surface through cracks in Earth’s crust. This makes new
crust. Does that mean there is more crust on the surface of Earth now than in the past?
That doesn’t make sense. Geologists had a theory to explain the phenomenon.
If Earth oozed molten magma in one place, then it must reabsorb crust somewhere
else. Sure enough, studies reveal that the Atlantic Ocean floor is expanding and the
Pacific Ocean floor is shrinking. New crust is made in the Atlantic Ocean, and is
destroyed in the Pacific.
Geologists found that the Pacific Ocean floor dives down into deep trenches under
continents. These trenches are called subduction zones. The expanding and shrinking
ocean floors are an example of how Earth is
really a recycler. Rocks are created and later
recycled. Proof of recycling rocks comes from
mapping earthquakes and volcanoes. Most
of them are found near undersea ridges and
subduction zones.
Comprehension Question
Describe how the layers of the Earth
interact.
50
#50160—Leveled Texts for Science: Earth & Space Science
© Shell Education
Structure of the Earth
Have you ever wondered how Earth is put together? Most people live their lives every
day without thinking about the planet under their feet. Some people do: they wonder
about Earth; they investigate it, they theorize about it, and they explore it. These people
are geologists, and they study Earth and how it is structured. They have discovered a
number of interesting things.
crust
mantle
outer
core
inner
core
For Eggsample...
Imagine Earth as a hard-boiled egg: an egg has a shell and Earth has a crust; an egg
has liquid under its shell and Earth has hot magma under its crust. If Earth were an
egg, it would be a 6,400-kilometer (4,000-mile) trip from its shell (the crust) down to its
center!
We live on Earth’s crust, the cooled and hardened outer shell of the planet. All of the
continents of Earth are a part of the crust, and so is the ocean floor.
Just like a cracked eggshell, Earth’s crust is cracked into multiple pieces. If you look
at the edges of the continents, you might notice that they look like cracks on an eggshell.
Earth also has other layers beneath the crust. They are the mantle and the outer and
inner cores. These layers are made of magma, or molten rock, and their temperatures
range from hundreds to thousands of degrees Fahrenheit.
51
© Shell Education
#50160—Leveled Texts for Science: Earth & Space Science
Recycling Crust
Molten magma rises to the surface through cracks in Earth’s crust; when it cools, it
creates new crust. That implies that there is more crust on Earth’s surface today than
there was millions of years ago. However, that couldn’t be right, so geologists had a
theory to explain the phenomenon.
If Earth oozed molten magma in one place, then it must reabsorb crust somewhere
else. Sure enough, studies reveal that the Atlantic Ocean floor is expanding and the
Pacific Ocean floor is shrinking. New crust is made in the Atlantic Ocean, and is
destroyed in the Pacific.
Geologists found that the Pacific Ocean floor dives down into deep trenches
under continents. These trenches are called
subduction zones. The expanding and
shrinking ocean floors are an example of
how Earth is really a recycler. Rocks are
created and later recycled. Proof of recycling
rocks comes from mapping earthquakes and
volcanoes. Most of them are found near
undersea ridges and subduction zones.
Comprehension Question
Describe how material is recycled through
the different layers of the Earth.
52
#50160—Leveled Texts for Science: Earth & Space Science
© Shell Education