By Jim Donahue
As previously stated, one of the potential happenings of the coming planetary alignment may be polar shift, or in the worst case scenario, pole reversal. First let’s talk about polar shift, which is referred to as polar wander.
Polar wander is a solid-body rotation of a planet or moon with respect to its spin axis, causing the geographic locations of the North and South Poles to change. In a stable state, the largest moments of inertia axis is aligned with the spin axis, with the smaller two moment of inertia axes lying in the plane of the equator. If this is not so, true polar wonder will occur: The planet or moon will rotate as a rigid body to realign the largest moment of inertia axis with the spin axis.
Cases of true polar wander have occurred several times in the course of the Earth’s history. The speed of rotation is limited to about 1° per million years.
Mars, Europa and Enceladus are also believed to have undergone true pole wander, in the case of Europa by 80°, flipping over almost completely.
Uranus’ extreme inclination with respect to the ecliptic is also an instance of true polar wander. It is believed to be the result of a catastrophic series of impacts that occurred billions of years ago.
The slow drift, about 20 meters since 1900, is partly due to motions in the Earth’s core and mantle, and partly to the redistribution of water mass as the Greenland ice sheet melts, and to isostatic rebound, the slow rise of land that was previously occupied by ice sheets or glaciers. The drift is roughly along the 80th meridian west.
The Chandler wobble is a small motion in the Earth‘s axis of rotation relative to the Earth’s surface, which was discovered by American astronomer Seth Carlo Chandler in 1891. It amounts to 30 ft on the Earth’s surface and has a period of 433 days. This wobble combines with another wobble with a period of one year so that the total polar motion varies with a period of about seven years.
The Chandler wobble is an example of the kind of motion that can occur for a spinning object that is not a sphere. The direction of the Earth’s spin axis relative to the stars also varies with different periods, and these motions, which are caused by the tidal attraction of the Moon and Sun, are called nutations.
What all of this means is that polar shift is happening all the time, and has done so forever. What may happen on or around 12/21/2012 is a cataclysmic pole shift.
The cataclysmic pole shift hypothesis suggests that there have been geologically rapid shifts in the relative positions of the modern-day geographic locations of the poles and the axis of rotation of the Earth, creating catastrophes’ such as tectonic events and floods.
More on tectonic events and floods tomorrow.
Complete polar reversal, referred to as ‘geomagnetic reversal’ is a change in the Earth’s magnetic field whereas the positions of magnetic north and magnetic south are interchanged. The Earth‘s magnetic field has alternated between periods of normal polarity, in which the direction of the field was the same as the present direction, and reverse polarity, in which the field was the opposite. These periods are called chrons. The time spans of chrons are randomly distributed with most being between 0.1 and 1 million years with an average of 450,000 years. Most of these reversals are estimated to take between 1,000 and 10,000 years. The latest one, the Brunhes–Matuyama reversal, occurred 780,000 years ago. This may indicate that we are overdue for a reversal; however you can see that this event takes quite a bit of time. In my opinion, instantaneous reversal won’t happen.
Coming tomorrow: Floods, Earthquakes and Volcanic eruptions.