The Earth has several poles, not just two. It has geographic
north and south poles, which are the points that mark the
Earth's axis of rotation. It also has magnetic north and south
poles, based on the planet's magnetic field. When you use a
compass, it points to the magnetic north pole, not the
geographic North Pole. The Earth's magnetic poles move. The
magnetic North Pole moves in loops of up to 50 miles (80 km) per
day. But its actual location, an average of all these loops, is
also moving at around 25 miles a year [ref]. In the last 150
years, the pole has wandered a total of about 685 miles (1102
kilometers). The magnetic South Pole moves in a similar fashion.
The poles can also switch places. Scientists can study when this
has happened by examining rocks on the ocean floor that retain
traces of the field, similar to a recording on a magnetic tape.
The last time the poles switched was 780,000 years ago, and it's
happened about 400 times in 330 million years. Each reversal
takes a thousand years or so to