Natural Remanent Magnetism
- The magnetization retained by rocks from previous magnetic fields,abbreviated NRM. NRM is a record of the Earth's magnetic field as it existed at the time that the rock formed, such as when magnetic crystals in igneous rocks solidified (also known as chemical remanent magnetism, CRM) or at the time of deposition of sedimentary rocks (known as depositional remanent magnetism, DRM). During deposition of sediments that become sedimentary rock, magnetized particles can settle with their magnetic pole aligned with that of the Earth at that time.
- geomagnetic polarity reversal