Zone where the magnitude and/or orientation of the earth's magnetic field is notably higher or lower than adjacent areas.

The amount by which a local measurement of the magnet field intensity exceeds or falls below the intensity of the global magnetic field.

The difference between the expected strength of the Earth's magnetic field at a certain location and the actual measured strength of the field at that location.

An increase or decrease in the local magnetic field compared to the normally expected value.

A deviation of observed magnetic inclination or intensity (as measured by a magnetometer) from a constant normal value.

a measurable change in the magnetic field strength due to the presence of magnetized rock