Historically, the magnetic poles have always been in motion, and they have flipped periodically, south to north and north to south. The last complete switch took place about 780,000 years ago. Rock formations carry evidence of the direction of the magnetic field for scientists to interpret. In the rock, the direction of the magnetic field shows these complete switches take from 1000 to 10,000 years to complete. No catastrophic events, such as the loss of a plant or animal species, correspond to these complete switches.
How do the poles move?
The Earth’s core is made of iron, and the core is so hot that the outside of the core is molten. The flow of molten iron sets up electric currents that in turn have associated magnetic fields. The magnetic fields from the core protect the Earth and its residents from the magnetic storms coming from the solar wind and from the activity of the sun.
Currently, the North Pole is moving faster than the South Pole. The North Pole is moving at a pace of forty miles per year toward Siberia. It is located at about 85 degrees latitude. The South Pole is moving at a pace of around thirty miles per year and is located at about 65 degrees latitude. Surprisingly, the poles are not 180 degrees apart.
Magnetic north vs true north
Magnetic north is different relative to north on a map depending on the location of the compass and map reader at the time of the reading. For example, magnetic north in Seattle points twenty degrees east of true north. In Maine, magnetic north points twenty degrees west of true north. This difference is called declination.
There are declination charts or maps to indicate the declination for the present location of the map reader. Airline pilots, hikers and other compass users must refer to current charts, because the movement of the poles changes the declination. Global positioning systems (GPS) have helped reduce the reliance on compass readings.
Consequences of change
Movies and science fiction sometimes use a catastrophic change in the Earth’s magnetic field as a plot device. Fortunately, scientists see no evidence of a catastrophic event due to magnetic field change. When a change occurs, the magnetic field may weaken and the Earth may be slightly more susceptible to the magnetic storms of outer space. That in turn may cause some disruption of man-made electronic items and possibly the power grid.
Meanwhile, the shift in magnetic north has caused the Tampa International Airport to rename the runways, which are numbered based on compass headings, and replace some signs. In practical terms, the shift in the poles is real, but hardly cataclysmic.
Source:
Following a Wandering North Pole, Science Friday, January 14, 2011. Ira Flatow interviews Prof. Ronald Merrill, University of Washington, Seattle.
Eilene Toppin Ording - Eilene Toppin Ording comes from a wide industrial and educational background. A farmer's daughter from Minnesota, Eilene is an active ...
