How do geologists know that the magnetic field of Earth has changed constantly over time?
A) by the direction of historical lava flows, which they have been able to date with radioactive dating methods
B) by crystals that have formed in metamorphic rocks
C) by records kept in magnetic rock-forming minerals
D) by analyzing and extrapolating records kept by scientists since the 1600s

Question

Quizplus · Accepted Answer

Geologists study the magnetic signatures in rock-forming minerals, which record the Earth's magnetic field at the time they were formed. This is known as paleomagnetism and provides evidence of changes in the Earth's magnetic field over geological time.

How Do Geologists Know That the Magnetic Field of Earth