Answer:
measuring seismic wave activity
Explanation:
the earths interior is made up of a number of layers such qs the crust, mantle, outer and inner cores.
The sun rises due east and sets due west.
that would be a primary source because it actually is his hat not a replica. a primary source is a firsthand, or the excerpt of someone who was actually there.
1. Crust
2. Mantle
3. Inner core
4. Outer core
