Download The Earth`s Internal Structure Descriptions and Explanations

The Earth's Internal Structure
A Scientific Illustration!
Read the following information to create scale pictures that show the structure of the earth and support these
pictures with explanations and descriptions in response to the questions below.
Earth’s History
Plasticity
Five billion years ago the Earth was formed in a
massive conglomeration and bombardment of
meteorites and comets. The immense amount of heat
energy released by the high-velocity bombardment
melted the entire planet, and it is still cooling off today.
Denser materials like iron from the meteorites sank
into the core of the Earth, while lighter silicates, other
oxygen compounds, and water from comets rose near
the surface.
The crust and the upper part of the mantle behave
similarly in that they are cool and rigid. For this reason,
this layer is classified as the lithosphere and extends
from the Earth’s
surface down 50 to
250 km (30 to 150
miles).
Directly
beneath
the
lithosphere
the
earth is especially
soft and plastic and
is
called
the
asthenosphere. A heavy load on the lithosphere like
an ice cap, large glacial lake, or mountain range can
bend the lithosphere down into the asthenosphere,
which can flow out of the way. The load will sink until it
is supported by buoyancy. If an ice cap melts or lake
dries up due to climatic changes, or a mountain range
erodes away, the lithosphere will buoyantly rise back up
over thousands of years.
Categorizing Earth’s Layers
The earth is classified into layers using two different
systems. There is the chemical composition
system which differentiates layers based on the
elements and compounds they contain, for example
iron, nickel, or aluminum silicates. The second system
distinguishes layers based on mechanical
properties, i.e. whether the layers are stiff and rigid
or soft and plastic.
Chemical Composition
Chemically speaking, the earth is divided into four main
layers: the inner core, outer core, mantle, and
crust. The core is composed mostly of iron and nickel
and is so hot (roughly 5000°C) that the outer core is
molten. The inner core, while extremely hot, is under
such extreme pressure that it remains solid. Most of
Earth's mass is in the mantle, which is composed of
iron, magnesium, aluminum, and oxygen silicate
compounds. The crust is much thinner than the other
layers and is composed of low density calcium, sodium,
and aluminum-silicate minerals.
The very center of the earth is approximately 6,375 km
(3,825 mi) deep. The outer core begins approximately
2,900 km (1,740 mi) beneath the earth’s surface and
the inner core begins about 5,100 km (3,060 mi)
beneath the surface. The crust is very thin and ranges
from 5 to 100 km (3 to 60 mi) deep. The mantle lies
between the crust and the outer core.
What’s the evidence?
How were the Earth's layers discovered? Recordings of
seismic waves from earthquakes gave the first clue.
Seismic waves will bend and reflect at the interfaces
between different materials. Studies of these wave
patterns have shown that some areas are solid while
others are fluid.
The fact that Earth has a magnetic field is an
independent piece of evidence for a molten, liquid outer
core. Circulation and convection of electrically
conductive molten iron in the Earth's outer core is
thought to produce the magnetic field. To make the
magnetic field, the circulation of matter must be
relatively rapid (much faster than it is in the plastic
mantle), so the core must be fluid.
Descriptions and Explanations
Include your responses to the following questions
in captions to explain your drawings. Use your own
3. What are the characteristics of the crust?
words!
4. What are the characteristics of the mantle?
1. What reason is given for why the earth contains so
much heat?
2. Explain the two ways in which the earth’s layers
have been categorized.
5. What are the characteristics of the core (inner and
outer)?
6. What characterizes the lithosphere?
7. What characterizes the asthenosphere?
Making your picture to Scale:
Part of your assignment is to make two scale drawings of the earth’s layers,
one for the crust, mantle and inner and outer core, and one that shows the
lithosphere and asthenosphere. Each will be in the shape of a wedge with
the bottom point of the wedge being the center of the earth.
Earth’s
Center
Follow these steps to determine the scale of your drawings:
1. Begin by finding the distance from the surface of the earth to the center
of the earth. Let’s call this “x” for now.
2. Determine the total length (in cm) you would like your drawing to be. Let’s call this distance “y”.
y
3. Divide y by x to get your scale factor. ( )=scale factor
x
4. Now you multiply this scale factor by every measurement you plan to have on your poster to find out where it
goes. For instance, if you are drawing the bottom depth of the crust, multiply the average crust depth by your
scale factor and that will tell you how far down (in cm) it should go on your paper.
Please ask questions if you feel uncertain about how to do this!
Assignment: Your assignment is to create a scientific illustration that is supported with explanations and
descriptions. It must include the following information:
• A title with your name directly beneath it.
• Two side-by-side wedge drawings (these could be 3-dimensional if you are clever) that depict the layers of
the earth and are drawn to scale. The first will show the crust, mantle and inner and outer core, while the
second will show the lithosphere and asthenosphere.
• Large, clear labels that give the names of the layers, the depths, and other characteristics (e.g. chemical
composition, etc.).
• Explanations and descriptions in response to the previous 7 questions (these may go with the labels or be on
their own).
• A scale that is large and easy to see that reads “1 cm = _____ km and 1 cm = _____ miles”. You can set up
a proportion to do this, for example:
22 cm = 1 cm
6375 km
x
•
In the example, 22 cm is the total length of the drawing. To solve, simply cross-multiply and divide. (Ask
me for help if you need it!)
And been neatly drawn and written, is colored, and shows careful attention to detail.
Sample of what the finished product may look like (although the labels are incorrect and the descriptions are not
adequate, not complete, and not related to the Earth):
Correct fomat poster: by Balsiger
Crust: The characteristics are much like on pizza…
Mantle: The mantles is useful because I put pictures on…
Inner core: Has characteristics such as where the seeds are…
Outer core: Protection for the seeds…
Scale=
1 cm=1 km
1 cm = 82 Mi
Lithosphere: A bubble made with Lith soap…
Asthenosphere: A small ball usually sold as a dog toy…
There are two different ways
that the earth’s crust has been
characterized… insert your
own words……………
The earth contains so much heat
because… insert your own
words………………………………
………………………………………
…