Information on declination for a region can be represented by a chart with isogonic lines (contour lines with each line representing a fixed declination).Near the surface of the Earth, its magnetic field can be closely approximated by the field of a magnetic dipole positioned at the center of the Earth and tilted at an angle of about 11° with respect to the rotational axis of the Earth.Calculations of the loss of carbon dioxide from the atmosphere of Mars, resulting from scavenging of ions by the solar wind, indicate that the dissipation of the magnetic field of Mars caused a near total loss of its atmosphere.The polarity of the Earth's magnetic field is recorded in igneous rocks, and reversals of the field are thus detectable as "stripes" centered on mid-ocean ridges where the sea floor is spreading, while the stability of the geomagnetic poles between reversals has allowed paleomagnetists to track the past motion of continents.Its magnitude at the Earth's surface ranges from 25 to 65 microteslas (0.25 to 0.65 gauss).Roughly speaking it is the field of a magnetic dipole currently tilted at an angle of about 11 degrees with respect to Earth's rotational axis, as if there were a bar magnet placed at that angle at the center of the Earth.A minimum intensity occurs in the South Atlantic Anomaly over South America while there are maxima over northern Canada, Siberia, and the coast of Antarctica south of Australia.The inclination is given by an angle that can assume values between -90° (up) to 90° (down).
Since the north pole of a magnet attracts the south poles of other magnets and repels the north poles, it must be attracted to the south pole of Earth's magnet.
In the northern hemisphere, the field points downwards.
It is straight down at the North Magnetic Pole and rotates upwards as the latitude decreases until it is horizontal (0°) at the magnetic equator.
Reversals also provide the basis for magnetostratigraphy, a way of dating rocks and sediments.
Although the magnetic declination does shift with time, this wandering is slow enough that a simple compass remains useful for navigation.