|Geophysicists believe that the Earth is
divided into numerous
shells, each with different
physical and chemical properties. Because we can’t collect samples from the center of the Earth, we base our models on indirect evidence,
such as data from
To construct a model of the Earth’s interior, we use a variety of geophysical observations. Estimates of the Earth’s dimensions are combined with measurements of gravitational acceleration to determine planetary density. Precession rate is used to calculate the Earth’s moment of inertia, a measure of how mass is distributed within the planet. Arrival times of seismic waves at different seismometers on the Earth’s surface are used to infer the physical properties of rocks and how they vary with depth. Shadow zones of seismic waves show that the Earth has two distinct layers, a mantle and a core (Fig. 1).
Fig. 1: Internal structure of the Earth.
|In the tradition of Sherlock Holmes, we pool different lines of evidence to create a comprehensive model of the Earth’s interior. We must reevaluate our model whenever investigations bring to light new clues about the Earth’s interior.|
Houghton Mifflin Company. All Rights Reserved.|
Terms and Conditions of Use, Privacy Statement, and Trademark Information