Answer Key
Chapter 7, Section 1, pages 190-196
Directed Reading A: Inside the Earth
Section: Inside the Earth
1. The Earth is composed of several layers.
THE COMPOSITION OF THE EARTH
C __ 2.A substance composed of two or more elements is a(n)
a. mix.
c. compound.
b. amalgam.
d. complex.
3. Complete Sentence - Why do less dense compounds make up Earth’s crust
while the densest compounds make up the core?
Heavier elements are pulled to the center of the Earth by gravity. The
elements with less mass are further from the center.
4. List the three layers of the Earth, based on their chemical composition.
Crust, mantle, core (outer and inner)
5. Complete Sentence - What three elements make up most of the Earth’s crust?
The three main elements that make up Earth’s crust are oxygen, silicon,
and aluminum.
6. Complete Sentence - Oceanic crust is denser than the continental crust
because it contains more of which three elements?
The oceanic crust contains more iron, calcium, and magnesium which
cause it to be denser than continental crust.
7. The mantle is composed of more of the element magnesium than the crust is.
8. Complete Sentence -Why do scientists look to the ocean floor to research the
mantle?
Scientists look at the ocean floor because magma from the mantle flows
out of active volcanoes on the ocean floor.
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Plate Tectonics
Directed Reading A continued
9. The mantle has less aluminum and less silicon than the
crust does.
10. Complete Sentence - What element makes up most of the Earth’s core?
Iron makes up most of Earth’s core.
11. Complete Sentence - How much of the Earth’s mass is made up by the core?
One third or 33% of the Earth’s mass is in the core.
THE PHYSICAL STRUCTURE OF THE EARTH
Match the correct description with the correct term. Write the letter in the space
provided.
B ___ 12. the outermost, rigid layer of the Earth
A ___ 13. a layer of slowly flowing rock in the mantle
D ___ 14. the liquid layer of the core
a.
b.
c.
d.
e.
asthenosphere
lithosphere
mesosphere
outer core
inner core
E ___ 15. the solid layer of the core
C ___ 16. the strong, lower part of the mantle
TECTONIC PLATES
C ___ 17. Large pieces of the lithosphere that move around on the asthenosphere
are called
a. mantle pieces.
b. crust pieces.
c. tectonic plates.
d. puzzle pieces.
18. Complete Sentence - Why are tectonic plates like the pieces of a jigsaw
puzzle?
Tectonic plates are like pieces of a jigsaw puzzle because the plates fit
together with other plates.
19. Complete Sentence - What are the two kinds of crust that a tectonic plate may
contain?
The two types of crust that a tectonic plate may contain are oceanic and
continental.
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Plate Tectonics
Directed Reading A continued
20. List three ways in which tectonic plates floating on the asthenosphere are
similar to ice cubes filling a punch bowl.
plates cover the surface of the asthenosphere
plates touch each other
larger plates displace more of the asthenosphere than small plates
MAPPING THE EARTH’S INTERIOR
D ___ 21. What do scientists use to study Earth’s interior?
a. sea-floor spreading rates
b. magnetic reversals
c. global positioning system
d. seismic waves
C ___ 22. What are seismic waves?
a. movements in the outer core
b. pictures of the Earth’s interior
c. vibrations from an earthquake
d. vibrations from a seismograph
23. Complete Sentence - Will a seismic wave traveling through a solid go faster
or slower than a seismic wave traveling through liquid? Explain your answer.
Seismic waves traveling through a solid will move faster than a seismic
wave traveling through a liquid. The speed of the seismic wave will
depend on the density and composition of material they pass through.
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Plate Tectonics