Although we don't know for sure, changes in the strength and orientation of earth's magnetic field are most likely due to
A) fluctuations in outer-core convection.
B) variations in sea-floor spreading rates.
C) the total number of mantle hot spots.
D) changes in the velocity of subducting plates.

Question

Quizplus · Accepted Answer

Fluctuations in outer-core convection are believed to be the primary cause of changes in the strength and orientation of the earth's magnetic field. This is supported by evidence such as correlations between changes in the magnetic field and variations in the Earth's rotation rate, as well as observations of magnetic field anomalies associated with areas of intense convection in the outer core.

Although We Don't Know for Sure, Changes in the Strength