Question

The image below shows Earth's layers.

a cutaway view of Earth showing Earth's layers with highest temperatures at the inside and lowest temperatures more toward the surface
Image courtesy of National Park Service

Which statement best explains the high temperatures in Earth's core?
A.
S waves and P waves absorbed by the mantle and crust gain heat, which moves toward the core.
B.
The high temperatures in the core are partly due to the absorption of heat energy from the Sun.
C.
S waves and P waves given off by the core release heat, which produces high temperatures in the core.
D.
The high temperatures in the core are partly due to the heat given off by decaying atoms.

Answer 1

D

The core’s high temperature is partly from heat released by radioactive decay of unstable isotopes (and from leftover heat of Earth’s formation and ongoing gravitational compression), not from sunlight or seismic waves.