Download Earth`s Interior Reading Packet 1

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Obiectives
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Describe and compare the crust, mantle, and core,
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Describe the structure of the lithosphere.
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Explain why matter within the asthenosphere moves.
Layer by Layer
Make a list of different
objects that are made uP of
layers. Classify the obiects
into groups based on the
number, type, or thickness
of their layers. Do most of
the objects contain soft or
hard centers?
ts Make a model of the earth and its layers.
fE-'a, he rocks, soil, and water you can see on the
ffi earths surface make up only a tiny fraction of the
&- total mass and volume of the earth' What is the
earth like below its surface? What makes up the interior
of our planet?
At one time, some people thought the earth might be
hollow. They imagined a person couid find cracks in the
surface that would lead them into enormous underground caverns. In 1864, French writer Jules Verne
wrote about just such an adventute inJoumey to the
Center of the Earth.In this book, three explorers go deep
into the earth and encounter a huge sea, prehistoric animals, and monster mushrooms. Today, scientists know
there are no open, hollow spaces deep in the earth. But
they also know that it is not all solid rock.
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What would you find if you could bore a hole
down deeper and deeper into the earth until you
reached its center? First, you would find that the
chemical makeup of the materials changes as
you go deeper. Second, you would discover that
the materials increase in density. Third, you
would observe that temperature and pressure
increase with depth, but at different rates.
Because of the way these factors interact, the
materials of the earth's interior form layers. Earth
scientists classify these layers in two different
ways. In one method of classification, the layers
are distinguished by differences in chemical makeup'
In the oth"er methoi of classification, the layers are
divided according to differences in physical properties.
Chapter
Figure 3.1
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Even the deePest caverns are
nowhere near the earth's
interior,
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Structure of the
Earth ,5
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lrs of the Earth
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Matter is made up of nearly 100 different chemical
elements. Different combinations of these elements
form different kinds of matter. When the layers of the
earth are divided according to the elements contained
in their matte6 three layers can be distinguished. The
outermost layeq, the crust, and the middle 1ayer, the
mantle, both contain materials called silicates. Silicates
are made of silico;r and oxygen combined with other
elements. The silicates of the crust are rich in aiuminum,
iron, and magnesium. In contrast, the silicates of the
mantle contain mostly iron and magnesium. The innermost layer, the core, is made up primarily of iron and
nickel, both metals.
: - ;e rocky silicate mater;.Xt of the crust contains
tflUch aluminum, and
t*"'rre silicon and oxygen
:':",E*n the rocks of the
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a;.rtle. The thickness
, ,,"-:he crust varies from
to 5o km.
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Core
The metals iron and
nickel make up most o[
the earth's core. The core
is very dense, accounting
for 32 percent of the
earth's mass but only
16 percent of iLs volume.
Mantle
The dense, roclcy silicates
of the mantle contain
large amounts of iron
and magnesium. The
mantle makes up about
82 percent of the earth's
volume and 68 percent of
its mass.
Chapter
3
Structure of the Earth
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The temperatures deep inside the earth are high
enough to melt the silicates and other substances that
make it up. Yet most of the earth's interior is not liquid'
Why? The enormous pressures inside the earth offset
the high temperatures. In much of the earth's interior,
high pressures will not allow the matter to melt'
The balance between temperature and pressure in
the earth varies with depth. Depending on this balance,
the matter can be solid, Iiquid, or in-between' Earth scientists divide the earth into five separate layers based
on these physical properties. The outermost layer, the
tithosphere (LITH uhs neen), is cool and rigid' The
Iayer below it, the asthenosphere (as THEHN uhs nnBn'),
is hot and semiliquid.
Chapter
3
Structure of the Earth
57
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Crust
What objects besides the
have a crust? How are
=arth
:heir crusts similar to and dit
ierent from the earth's crust?
.ook up the word crustin
rhe dictionary. How does
crust apply to the earth's
cutermost layer?
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The crust is the only layer of the earth that people
have direct contact with. Together with the upper mantle, it forms a cool, rigid laye4 the lithosphere, which
undergoes slow but important changes. These changes,
which you will learn about in later chapters, affect the
earth's surface and its living things.
The lithosphere, Iike the rest of the earth, has a layered structure. You already know that it includes the
crust and upper mantle. But the crust itself is made up
of two sepaiate layers, called continental crust and
oceanic crlrst. Look at Figure 3.3 below. It is a cross section of the lithosphere showing these layers. Notice that
where continents are, the crust has both layers' Continental crust lies above oceanic crust. Under the oceans,
in contrast, there is only oceanic crust'
How are these two layers of crrst different?
Continental crust is less dense than oceanic crust'
Compared to oceanic crust, it is made up of a higher
percentage of silicon and oxygen, and contains more
aluminum. The rocks that make up continental crust
are mostly granite and rhyolite. Denser, darker rocks
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firucuur"e,;rl;hc
Liuiaq]siff
called basalt and gabbro make up oceanic crust'
Continental cmst, as you can see in Figure 3'3,
varies in thickness. Tall mountains have deep "roots'"
You can stand on lop of a tall mountain and have over
40 km of continental crust below you' At a continent's
edge, in contrast, the thickness of continental crust
thins to zero.
igure 3.3 P
he lithosphere has a laYered
:ructure. What part of the
:hosphere contains continental
rust? i'':I'i
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Chapter
3
Structure of the Earth
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The material of the asthenosphere is
iike thick liquid or hot tar. As intense
heat from the earth's core moves toward
the surface through the mantle, it causes
the material of the asthenosphere to circulate. Matter rises through certain parts
of the asthenosphere. Then it cools and
slowly sinks in other places. The result
is a circular flow of matter called
convection (kuhn VEHKT shuhn).
Convection in the asthenosphere is
shown in Figure 3.4. This circulation is
so slow that a piece of rock may take
millions of years to rise through the
asthenosphere. Yet this movement has a
very imporLant effect on the lithosphere
above, as you will find out in Chapter 5.
Figure 3.4
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Matter in the asthenosphere moves slowly by
convection.
Temperature Changes in the Earth
Most of the earth's surface and its underlying
crust are cool, Below the crust, however, the
How does the temperature of the earth's interior increase with depth? This is an important
question, because the temperature and pressure
at a particular depth determine whether the
materialthere will be solid, liquid, or plastic.
Use the table of data at the right to make a
i,9raph showing how temperature increases with
depth. Then answer the questions below.
:
On whicfr axis didyou,put depth? Why?.'
What would your graph look like if you put
,
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What is the shape of the curve on your
graPh?
50 km
20'c
500'c
100 km
900"c
150 km
1,350'C
200 km
1,550'C
300 km
1,600"c
400 km
'1,800'c
25 km
temperature begins to increase. At the earth's
center, the terrperature is estimated to be over
4,000"c!
d-epthonlheothbiaxis?''' r',
Estimated Temperature
Deptlt
13. Where on the curve does.temperature
' increase atthe fastest rate? The slowest?
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Your'graph goes:to 400 km'in depth. Where
in the earth is this? Through which layers do
,ln,a short paragraph, describe whatthe graph
tells:y.ou about the earth's interioli; :
,
Chapter
3
Structure of the
'
Earth
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