Scientists tell us that our magnetic poles have reversed in the past, and that they will again. The last one occurred 780,000 years ago. The average time period between reversals is 450,000 years, but there isn’t really any pattern, it is random. We are overdue by average only.
Scientists don’t really know how the process works, and are unable to predict the next reversal. They have been telling us that the process takes hundreds or thousands of years. Recent studies have shown that it can happen in the space of weeks or months, and I suggest it can happen overnight. Perhaps rapid reversals don’t leave much evidence – perhaps rapid reversals are quite common! For example, if it was normal for a double reversal to happen quickly – where the poles return to their original position – we wouldn’t know about any historical instances.
If a reversal involves a dramatic lessening of our geomagnetic field’s strength, then basically our shields are down, and cosmic rays reaching ground-level will greatly increase. Forget about navigational problems – we could be fried.
Studies have shown that pigeons have receptors in their brains that are sensitive to magnetic fields, and presumably those are a reason for their great navigation skills. It is possible that many other animals also have such receptors, but they don’t utilize them as obviously. So during a reversal, the chaos in the animal world could be significant – and of course humans are animals.
Scientists have not yet worked out what causes a magnetic reversal, but recent studies of Mercury suggest that the solar wind and particles from the Sun have an effect on planetary cores. My interpretation is that a massive solar storm could be the straw that breaks the camel’s back and trigger a reversal if the Earth is ready for one. The Electric Universe folk have also suggested that a highly-charged comet passing by could also do the trick. Or perhaps ocean currents, after being affected by climate change, are the trigger? And if climate change is caused by the Sun, then that ties in nicely with the first theory.
Another theory comes from Rich Muller:
where “lighter components, like oxygen, sulfur, and silicon . . . rise toward the core-mantle boundary (CMB).” Accumulating like sediment on the floor of the ocean, these “fall” upward from the core onto the surface of the mantle, which is uneven like the topography of the Earth’s surface. When enough sediment collects, it tumbles like an avalanche, into the outer core, thereby cooling it.
Rare events could trigger really big avalanches at the CMB, however. When a massive asteroid or comet slammed into Earth’s surface at an oblique angle, the lower mantle would jerk sideways, shearing off whole mountains of sediment. As the sediments slide up, a downward-sinking mass of cool iron could completely disrupt large convection cells. Although variously oriented local fields within the core would remain strong, at the surface Earth’s dipole magnetic field would collapse.
And according to Gary Glatzmaier reversals are rooted in chaos theory:
The resulting three-dimensional numerical simulation of the geodynamo, run on parallel supercomputers at the Pittsburgh Supercomputing Center and the Los Alamos National Laboratory, now spans more than 300,000 years.
Our solution shows how convection in the fluid outer core is continually trying to reverse the field but that the solid inner core inhibits magnetic reversals because the field in the inner core can only change on the much longer time scale of diffusion. Only once in many attempts is a reversal successful, which is probably the reason why the times between reversals of the Earth’s field are long and randomly distributed.
Rapid Magnetic Changes
NASA loves telling is that a magnetic reversal takes thousands of years, and that we have nothing to fear. I suggest that NASA should pay more attention to scientific studies that suggest otherwise:
…a new study of ancient copper mines in southern Israel found that the strength of the magnetic field could double and then fall back down in less than 20 years. [Wired]
This lava, Bogue says, initially started to cool and then was heated again within a year as a fresh lava flow buried it. The fresh lava re-magnetized the crystals within the rock below, causing them to reorient themselves a whopping 53 degrees. At the rate the lava would have cooled, says Bogue, that would mean the magnetic field was changing direction at approximately 1 degree per week. [Wired]
Palaeomagnetic results from lava flows recording a geomagnetic polarity reversal at Steens Mountain, Oregon suggest the occurrence of brief episodes of astonishingly rapid field change of six degrees per day. The evidence is large, systematic variations in the direction of remanent magnetization as a function of the temperature of thermal demagnetization and of vertical position within a single flow, which are most simply explained by the hypothesis that the field was changing direction as the flow cooled. [Nature]
the spacing in time between successive flows erupted during a transition cannot be determined accurately because the errors associated with radiometric ages are typically much greater than the duration of a polarity transition. [The Magnetic Field of the Earth: Paleomagnetism, the Core, and the Deep Mantle, page 205]
The final quote suggests that we are not able to detect rapid transitions, and that estimates of durations lasting thousands of years are are a consequence of measurement limitations.
This is indisputable – the speed at which the magnetic north pole is moving (not necessarily in the same direction) has recently become much faster. Because this is the entirety of our studies, we don’t know what was normal prior to the 1500s…
Not only are the poles moving rapidly – the strength of our magnetic field is diminishing as well:
Rapid changes in the churning movement of Earth’s liquid outer core are weakening the magnetic field in some regions of the planet’s surface, a new study says.
“What is so surprising is that rapid, almost sudden, changes take place in the Earth’s magnetic field,” said study co-author Nils Olsen, a geophysicist at the Danish National Space Center in Copenhagen.
…The changes “may suggest the possibility of an upcoming reversal of the geomagnetic field,” said study co-author Mioara Mandea, a scientist at the German Research Centre for Geosciences in Potsdam. [National Geographic]
The Navigational Danger
Without our magnetic shield, technology will be more at risk from solar storms. The most at risk will be satellites – they are not designed to withstand solar storms in the absence of the magnetic field. So if our GPS satellites are knocked out, planes would be grounded.
Of course planes have old-school compasses as a backup, but these certainly will not be accurate during a magnetic pole shift. So even the possibility of GPS satellites failing would be enough to ground planes – otherwise they could lose navigation mid-flight.
Ships would face the same problems of course.
The Ozone Danger
It is expected that the Ozone Layer would disappear completely during a magnetic reversal (and return afterwards). See this NASA paper, Particle Events as a Possible Source of Large Ozone Loss during Magnetic Polarity Transitions.
Major solar storms during a reversal could cause ozone depletion. According to Wikipedia, humans would see at least 3x more incidences of skin cancer. The effects on all living things combined is hard to predict, but could be catastrophic when everything is added together.
The Power Grid Danger
One study has nominated massive solar storms as the trigger for a magnetic reversal. Another suggests global warming is the culprit – and global warming can be caused by increased solar activity. During a reversal our shields are down, and if there is a concurrent solar storm, the situation becomes worse again. Life on Earth won’t be affected in general, and societies that don’t rely on technology will be OK as well. The most modern societies would suffer terribly if the reversal is rapid. Power grids would fail (a major solar storm can wreck them, and a magnetic reversal would be much worse). With no electricity there is no water, no sewage being pumped, no gas stations operating, no deliveries of food. Emergency services will be compromised and unable to make much of a difference. Certainly millions would die, and a billion people would face great difficulties. Only those who have sensibly prepared by storing food and water will be able to cope.
The Cosmic Ray Danger
Detailed calculations confirm that, if the Earth’s dipole field disappeared entirely (leaving the quadrupole and higher components), most of the atmosphere could be reached by high energy particles. However, the atmosphere would stop them. Instead there would be secondary radiation of 10Be or 36Cl from collisions of cosmic rays with the atmosphere. There is evidence that this occurs both during secular variation and during reversals. [Wikipedia]
Our geomagnetic field is responsible for blocking out roughly 50% of cosmic rays [Nature]… so if our “shields are down”, cosmic radiation would double. While this would lead to increased mutations, double the current rate is nothing to worry about. However, two of the possible triggers for a magnetic pole shift are a result of increases in solar activity. This could result in an increased in charged particles from the Sun reaching Earth as well. And that could spell trouble.