The intensity of the magnetic field at the earth's surface is approximately 0.32 gauss at the equator and 0.62 gauss at the north pole.
A gauss equivalent to 1 maxwell per square centimeter and a maxwell is equivalent to the flux that produces one abvolt in a one-turn circuit when the flux is reduced to zero at a uniform rate in one second; while a flux is the electric or magnetic field lines of force that traverse a given cross-sectional area.
The earth's internal magnetic field reverses, on average, about every 300,000 to 1 million years.
This reversal is very sudden on a geologic time scale, apparently taking about 5,000 years.
The time between reversals is highly variable, sometimes less than 40,000 years and at other times as long as 35 million years and no regularities or period times have been discovered so far.
A long interval of one polarity may be followed by a short interval of an opposite polarity.