The sustained heat within the Earth's interior is attributed to: ...

[nmorano1]

The sustained heat within the Earth's interior is attributed to:
  a. Radioactive Decay
  b. Conduction
  c. Convection
  d. Isostatic Equilibrium

Question 2

If P and S waves were to travel at the same constant speeds, what could be inferred about the Earth's
  interior?
  a. The interior is density stratified.
  b. The interior is liquid.
  c. The interior is homogenous.
  d. The interior is solid

[parshano]

Answer to Question 1

ANS: A
Radioactive decay occurs when the nuclei of unstable elements begin to break apart. As the radioactive
particles are ejected, heat is given off. The residual heat combined from radioactive decay combined
with the energy given off when the iron melted into the core sustains Earth's internal heat. Information
can be found in the section A New Understanding of Earth Evolved Slowly.

Answer to Question 2

ANS: C
If the interior of Earth was homogenous, they waves would travel through it at the same speed and in a
straight line. Information can be found in the section The Study of Earthquakes Provides Evidence of
Layering.