Geomagnetic excursion
From Wikipedia, the free encyclopedia
A geomagnetic excursion, like a geomagnetic reversal, is a significant change in the Earth's magnetic field.
Unlike reversals however, an excursion does not permanently change the
large-scale orientation of the field, but rather represents a dramatic,
typically short-lived decrease in field intensity, with a variation in
pole orientation of up to 45 degrees from the previous position. These
events, which typically last a few thousand to a few tens of thousands
of years, often involve declines in field strength to between 0 and 20%
of normal. Excursions, unlike reversals, are generally not recorded
across the entire globe. This is partially due to them not being
recorded well within the sedimentary record, but also because they
likely do not extend through the entire geomagnetic field. One of the
first excursions to be studied was the Laschamp event, dated at around
40 kyr ago. Since this event has also been seen in sites across the
globe, it is suggested as one of the few examples of a truly global
excursion.[1]
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[edit] Causes
Scientific opinion is divided on what caused geomagnetic excursions. The dominant theory is that they are an inherent aspect of the dynamo processes that maintain the Earth's magnetic field. In computer simulations, it is observed that magnetic field lines can sometimes become tangled and disorganized through the chaotic motions of liquid metal in the Earth's core. In such cases, this spontaneous disorganization can cause decreases in the magnetic field as perceived at the Earth's surface. In truth, under this scenario, the Earth's magnetic field intensity does not significantly change in the core itself, but rather energy is transferred from a dipole configuration to higher order multipole moments which decay more rapidly with the distance from the Earth's core, so that the expression of such a magnetic field at the surface of the Earth would be considerably less, even without significant changes in the strength of the deep field. This scenario is supported by observed tangling and spontaneous disorganizations in the solar magnetic field. However, this process in the sun invariabily leads to a reversal of the solar magnetic field (see: solar cycle), and has never been observed such that the field would recover without large scale changes in field orientation.The work of David Gubbins[2] suggests that excursions occur when the magnetic field is reversed only within the liquid outer core; reversals occur when the inner core is also affected. This fits well with observations of events within the current chron of reversals taking 3–7000 years to complete, while excursions typically last 500–3000 years. However, this timescale does not hold true for all events, and the need for separate generation of fields has been contested, since the changes can be spontaneously generated in mathematical models.
A minority opinion, held by such figures as Richard A. Muller, is that geomagnetic excursions are not a spontaneous processes but rather triggered by external events which directly disrupt the flow in the Earth's core. Such processes may include the arrival of continental slabs carried down into the mantle by the action of plate tectonics at subduction zones, the initiation of new mantle plumes from the core-mantle boundary, and possibly mantle-core shear forces and displacements resulting from very large impact events. Supporters of this theory hold that any of these events lead to a large scale disruption of the dynamo, effectively turning off the geomagnetic field for a period of time necessary for it to recover.
Except for recent periods of the geologic past, it is not well known how frequently geomagnetic excursions occur. Unlike geomagnetic reversals, which are easily detected by the change in field direction, the relatively short-lived excursions can be easily overlooked in long duration, coarsely resolved, records of past geomagnetic field intensity. Present knowledge suggests that they are around ten times more abundant than reversals, with up to 12 excursions documented within the current reversal period Brunhes–Matuyama reversal. end quote from Wikipedia.
To the most immediate effect upon our Earth due to this “magnetic pole anomaly,” this report continues, has been the "strange disruption" of the jet stream over the Northern Hemisphere that on the North American side has produced the driest and warmest winter weather in recorded history, but on the European side has caused record-setting cold and snow that has claimed over 650 lives.
Though Director Seleznyov notes in this report that the evidence for a “full scale” geomagnetic reversal of the positions of magnetic north and magnetic south are still being debated, our Earth is, “without a doubt,” currently undergoing a Laschamp-type geomagnetic “event” known as a geomagnetic excursion.
A geomagnetic excursion, like a geomagnetic reversal, is a significant change in the Earth’s magnetic field. Unlike reversals however, an excursion does not permanently change the large-scale orientation of the field, but rather represents a dramatic, typically short-lived decrease in field intensity, with a variation in pole orientation of up to 45 degrees from the previous position.
The Laschamp Geomagnetic "Event" noted in this report is interesting on a number of levels due to its having occurred between 7,000-17,000 years ago falling within the working timeframe of: 1.) The flash freezing of Siberia where still today woolly mammoths are still uncovered in near pristine condition, and 2.) The 11 August 3114 BCE start date of the Mayan Calendar that seemingly predicts the year of 2012 will, indeed, experience another such cataclysmic event. end quote from:
http://www.spiritofmaat.com/apr12/rapid_pole_shift.html
So, if I understand all this stuff correctly one of the things being talked about is that we may be in a geomagnetic excursion like the one that began the Mayan Calendar in the first place. That actually makes some sense that it would begin and end in the same kind of cycle. However, how did they know precisely when the next geomagnetic excursion would take place if this is true? And, if we are in the middle of a 2012 geomagnetic excursion what will be frozen in its tracks in place of the Mastodons being found with flowers in their mouths from Alaska to Siberia that froze in mid bite during the last geomagnetic excursion?
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