Understanding the Earth (Geology 111)
Fall 2009
Scale Model of Earth, Homework #1
Section 2: Due Thursday, Sept. 3 at the beginning of class
NAME_____________________________
Assignment: Build a scale model (2 dimensional) of Earth. We will place the boundaries for
various parts of Earth (e.g., mantle, core) on the scale model provided. We will also calculate
the volumes of the mantle and core.
Information needed for scale model: Below is a table of distance from the surface of earth to
various features of Earth. Note that the radius of Earth is 6378 km.
Feature of Earth
Distance from surface of Earth to (in
kilometers)
Base of continental crust
Base of oceanic crust
Base of mantle (Mantle/CoreBoundary)
Base of outer core
Base of lithosphere
Top of Mt. Everest
Bottom of ocean
“top” of Earth’s atmosphere
45
7
2900
5145
150
10
5
16
The scale model we will use is an Earth with a radius of 10 cm (get a copy from Steve OR draw
your own.
PLEASE SHOW YOUR WORK ON ALL OF THE CALCULATIONS BELOW
You will need to set up a ratio to determine the scaling factor:
Radius of the Earth =
Thickness of the layer
Radius of your model
Thickness of your layer on the model
and solve for the thickness of the layer on your model. If you are confused, please stop by and
ask me for help.
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How do we decide where to put these boundaries?
1. How many kilometers are represented by 1 cm on the scale model?
2. Now complete the table below.
(1km = 1000m; 1m = 100cm; 1 cm = 10mm)
Feature of Earth
Distance from
Distance on Distance on
surface of Earth to scale model scale model
(in kilometers)
in cm
in mm
Base of continental crust
45
Base of oceanic crust
7
Base of mantle
2900
Base of outer core
5145
Base of lithosphere
150
Top of Mt. Everest*
10
Bottom of ocean*
5
“top” of Earth’s atmosphere
16
*no need to include these on your diagram
Reminder: The outer part of the earth can be divided several ways, so these layers are not all one
on top of another.
3. With the above information, place the boundaries (where possible) of the features on the
scale model provided.
Information needed for calculating the volume of Earth, mantle and core:
Formula for volume of a sphere = 4/3  r3


Total volume of Earth ____________________
Radius of core ____________________
Total volume of core_____________________
Total volume of mantle and crust____________________
What is the percent of mantle (+crust) volume relative to whole Earth?____________
What is the percent of core volume relative to whole Earth?____________
4. On the 10cm radius circle provided (in class or in Steve’s mailbox), carefully draw in the
boundaries within the earth. Some of these lines may be close together, so be sure to draw your
lines neatly and precisely.
2