Which one of the following processes was important for melting the entire Earth about 4.6 billion years ago?
A) Radioactivity,or the spontaneous breaking apart of heavier nuclei into lighter nuclei
B) Tidal heating of Earth due to the combined gravitational pulls of the Sun and the Moon
C) Heat released by the condensation of water vapor into liquid water to form the oceans
D) Nuclear fusion,or the combining of lighter nuclei to form heavier nuclei

Question

Quizplus · Accepted Answer

Radioactivity is the process in which heavier nuclei break apart into lighter ones, releasing large amounts of heat in the process. This process played a significant role in the heating and melting of the Earth's interior during its formation about 4.6 billion years ago. Tidal heating and ocean formation are not large enough processes to cause the entire Earth to melt, and nuclear fusion is not a process that occurred during the Earth's formation, as it requires the extreme temperatures and pressures found only in stars.

Which One of the Following Processes Was Important for Melting