1. Inside the Earth Chapter 4 Section 1 p. 96 - 102 Vocabulary: 1. crust
2. mantle
3. core
4. lithosphere
5. asthenosphere
6. mesosphere
7. tectonic plate

2. The Composition of the Earth p. 96
Scientists think about physical layers of the Earth in two ways:
by their chemical composition and by their physical properties.
The Earth is divided into three layers – the crust, the mantle,
and the core – based on the compounds that make up each
of the layers. The less dense compounds make up the crust
and the mantle, and the densest compounds make up the
core.

3. The Crust p. 96
The outermost layer of the Earth is the crust. The crust is 5
to 100 km thick. It is the thinnest layer of the Earth.
There are two types of crust – continental and oceanic. Both
are made mainly of the elements oxygen, silicon and aluminum.

4. The Mantle p. 97
The layer of the Earth between the crust and the core is the
mantle. The mantle is much thicker than the crust and contains
most of the Earth’s mass.
No one has ever visited the mantle.
The crust is too thick to drill through to
reach the mantle. In some places, like
in this picture of an oceanic vent,
mantle rock pushes to the surface,
which allows scientists to the study the
rock directly. Magma from the mantle flows out of the active
volcanoes on the ocean floor. These underwater volcanoes
have given scientists many clues about the composition of the
mantle. The mantle contains more magnesium and less
aluminum and silicon than the crust, and so it is more dense
than the crust.

5. The Core p. 97
The layer of the Earth that extends from below the mantle to
the center of the Earth is the core. Scientists think that the
Earth’s core is made mostly of iron and contains smaller
amounts of nickel, but almost no oxygen, silicon, aluminum,
or magnesium. The core makes up about one-third of the
Earth’s mass.

6. The Physical Structure of the Earth p. 98 - 99
Another way to look at the Earth is to examine the physical
properties of its layers. The Earth is divided into FIVE physical
layers – the lithosphere, asthenosphere, mesosphere, outer
core and inner core. Each layer has its own set of physical
properties.

7. The Lithosphere
The outermost, rigid layer of the Earth is called the lithosphere.
It is made of two parts: the crust and
the rigid upper part of the mantle. The
lithosphere is divided into pieces
called tectonic plates.
The Asthenosphere
The asthenosphere is is a plastic
layer of the mantle on which pieces of
the lithosphere move. The asthenosphere is made of solid
rock that flows very slowly.

8. The Mesosphere
Beneath the asthenosphere is the strong lower part of the mantle,
called the mesosphere. The mesosphere extends from the
bottom of the asthenosphere to the Earth’s core.
Mesosphere
The Outer Core
The Earth’s core is divided into two
parts – the outer core and the inner
core. The outer core is the liquid
layer of the Earth’s core that lies
beneath the mantle and surrounds
the inner core.
The Inner Core
The inner core is the solid, dense, center of our planet that
extends from the bottom of the outer core to the center of the
Earth, which is about 6,380 km below the surface.

9. Tectonic Plates p. 100
Pieces of the lithosphere that move around on top of the asthenosphere
are called tectonic plates. Think of the lithosphere as a giant jigsaw
puzzle and the tectonic plates are the puzzle pieces.
Notice that each tectonic plate fits together with the tectonic
plates that surround it. Not all tectonic plates are alike. For
example, the South American plate has an entire continent
on it and has oceanic crust. The Cocos plate has only oceanic
crust. Some tectonic
plates, such as the
South American plate,
include both continental
and oceanic crust.

10. A Tectonic Plate Close-Up p. 101
This tectonic plate consists of the upper part of the mantle
and both oceanic crust and continental crust. The thickest
part of this plate is the continental crust. The thinnest part
is in the mid-Atlantic Ocean.

11. Mapping the Earth’s Interior p. 102
Although scientists have never drilled through the crust of the Earth, they
have learned a great deal about the inside of the Earth by studying earth
quakes. When an earthquake happens,
vibrations called seismic waves, are produced.
Seismic waves travel at different speeds
through the Earth. Their speed depends
on the density and composition of the
material they pass through. Seismic
waves travel faster through a solid
than through a liquid. Scientists
measure the distance and travel times
of these waves to calculate the density
and thickness of each physical layer
of the Earth.

12. Layers of the Earth Song

13. Quiz Time!
1. Name and describe the three layers that make up the Earth.
Crust is the outermost layer, 5 – 110 km thick, made up
mainly of oxygen, silicon, and aluminum
Mantle is the layer between crust and core, 2,900 km thick,
denser than the crust, contains most of the Earth’s mass
Core is the innermost layer, made up mostly of iron
2. What are the five physical layers of the Earth?
lithosphere, asthenosphere, mesosphere, inner core, and
outer core
3. True or False? The asthenosphere is the thinnest physical
layer.
False, the lithosphere is the thinnest layer

14. 4. The part of the Earth that is molten is the
A. crust
B. mantle
C. outer core
D. inner core C
5. The part of the Earth on which the tectonic plates move is
the
A lithosphere
B. asthenosphere
C. mesosphere
D. crust B

15. Science Humor… One student said to another…
I studied geology in sixth grade, but the curriculum was too
deep.
When I took geology, I went through a metamorphosis. Now
I dig the subject!
We had a great teacher. The class rocked!