Is a Pole Shift underway as we speak ? A geomagnetic reversal could have dire effects on our high tech lifestyles, temporarily knocking us back into the dark ages, time to get ready to be cave men again. If worst the case scenarios eventuates.
The British Geological Survey has reported as part of the ‘South Atlantic Anomaly and South Georgia Magnetic Observatory’ report that there may be some signs of the Earths magnetic pole shifting, a geomagnetic reversal.
The magnetic poles of the Earth are part of the magnetic field that surrounds the earth. This field is generated by the spinning core of the earth just like an electric motor and the poles are just the same as the poles on a bar magnet. While the earths North and South pole do wander around a bit, if you were to make timed observations of a compass you would see slight movements in where the compass points, a pole reversal refers to the switching of North and South magnetic poles, in effect the compass needle would swing 180 degrees. Once the poles have swapped place things continue on as normal, it makes surprisingly little difference which is actually north and south.
A geomagnetic reversal is much different to the Earth as a planet flipping over, during a geomagnetic reversal only the Earths magnetic field is effected, the physical location of the continents stays exactly the same.
Admittedly the ability of scientists to predict these events is very limited at best. The last geomagnetic reversal – Brunhes–Matuyama reversal – , occurred approximately 780,000 years ago so we are a little short on first hand accounts or evidence of what happens during this event, making it difficult to say what a pole shift looks like while its happening. The history of these geomagnetic reversals is stored in certain minerals when they are formed, the current north / south pole positions. The Global Polarity Timescale was built using the techniques that read this data and shows the history of these events as best we can tell.
The time a pole reversal takes, which is the most dangerous period for all the electric gadgets we love, can also vary widely. Past events have been recorded as taking 4 years and others up to hundreds of years.
Even the possible effects of the pole reversal vary widely amongst the scientific community. Some groups argue that as the magnetic poles are weak or gone completely during the reversal we will be susceptible to the radiation of the cosmic rays or solar flares, the magnetic field of the earth is our protective barrier from radiation in space – cosmic rays – so it disappearing isn’t good. The opposing groups conclude there is no evidence of major extinctions during these events, so there is no danger. Most everyone agrees that the technology we use today is the main thing in danger during a reversal.
As far as how serious a bitch slap in the face from mother nature this is, it’s not huge. She can punch a lot harder than this. At worst we just go old school for a little while, at best and in all likelihood there will be zero impact.
Pictures courtesy of NASA
Buddha’s Brother out.…
A geomagnetic reversal is a change in the Earth’s magnetic field such that the positions of magnetic north and magnetic south are interchanged. The Earth‘s 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 in the opposite direction. These periods are called chrons. The time spans of chrons are randomly distributed with most being between 0.1 and 1 million years. Most reversals are estimated to take between 1,000 and 10,000 years. The latest one, the Brunhes–Matuyama reversal, occurred 780,000 years ago. Brief disruptions that do not result in reversal are called geomagnetic
In the early 20th century geologists first noticed that some volcanic rocks were magnetized opposite to the direction of the local Earth’s field. The first estimate of the timing of magnetic reversals was made in the 1920s by Motonori Matuyama, who observed that the magnetic fields of some rocks in Japan were reversed and that these rocks were all of early Pleistocene age or older. At the time, the Earth’s polarity was poorly understood and the possibility of reversal aroused little interest.
Three decades later, when Earth’s magnetic field was better understood, theories were advanced suggesting that the Earth’s field might have reversed in the remote past. Most paleomagnetic research in the late 1950s included an examination of the wandering of the poles and continental drift. Although it was discovered that some rocks would reverse their magnetic field while cooling, it became apparent that most magnetized volcanic rocks preserved traces of the Earth’s magnetic field at the time the rocks had cooled. At first it was thought that reversals occurred approximately every million years, but by the 1960s it had become apparent that the timing of magnetic reversals was erratic.
During the 1950s and 1960s information about variations in the Earth’s magnetic field was gathered largely by means of research vessels. But the complex routes of ocean cruises rendered the association of navigational data with magnetometer readings difficult. Only when data was plotted on a map, did it become apparent that remarkably regular and continuous magnetic stripes appeared on the ocean floors.
In 1963 Frederick Vine and Drummond Matthews provided a simple explanation by combining the seafloor spreading theory of Harry Hess with the known time scale of reversals: if new sea floor is magnetized in the direction of the field, then it will change its polarity when the field reverses. Thus, sea floor spreading from a central ridge will produce magnetic stripes parallel to the ridge. Canadian L. W. Morley independently proposed a similar explanation in January 1963, but his work was rejected by the scientific journals Nature and Journal of Geophysical Research, and remained unpublished until 1967, when it appeared in the literary magazine Saturday Review. The Morley–Vine–Matthews hypothesis was the first key scientific test of the seafloor spreading theory of continental drift.
Beginning in 1966, Lamont–Doherty Geological Observatory scientists found that the magnetic profiles across the Pacific-Antarctic Ridge were symmetrical and matched the pattern in the north Atlantic’s Reykjanes ridges. The same magnetic anomalies were found over most of the world’s oceans, which permitted estimates for when most of the oceanic crust had developed.
Observing Past Fields
Originally, however, the past record of geomagnetic reversals was first noticed by observing the magnetic stripe “anomalies” on the ocean floor. Lawrence W. Morley,Frederick John Vine and Drummond Hoyle Matthews made the connection to seafloor spreading in the Morley-Vine-Matthews hypothesis which soon led to the development of the theory of plate tectonics. Given that the sea floor spreads at a relatively constant rate, this results in broadly evident substrate “stripes” from which the past magnetic field polarity can be inferred by looking at the data gathered from towing a magnetometer along the sea floor.
However, because no existing unsubducted sea floor (or sea floor thrust onto continental plates, such as in the case of ophiolites) is much older than about 180 million years(Ma) in age, other methods are necessary for detecting older reversals. Most sedimentary rocks incorporate tiny amounts of iron rich minerals, whose orientation is influenced by the ambient magnetic field at the time at which they formed. Under favorable conditions, it is thus possible to extract information of the variations in magnetic field from many kinds of sedimentary rocks. However, subsequent diagenetic processes after burial may erase evidence of the original field.
Because the magnetic field is present globally, finding similar patterns of magnetic variations at different sites is one method used to correlate age across different locations. In the past four decades great amounts of paleomagnetic data about seafloor ages (up to ~250 Ma) have been collected and have become an important and convenient tool to estimate the age of geologic sections. It is not an independent dating method, but is dependent on “absolute” age dating methods like radioisotopic systems to derive numeric ages. It has become especially useful to metamorphic and igneous geologists where the use of index fossils to estimate ages is seldom available.
Geomagnetic polarity time scale
Through analysis of seafloor magnetic anomalies and dating of reversal sequences on land, paleomagnetists have been developing a Geomagnetic Polarity Time Scale(GPTS). The current time scale contains 184 polarity intervals in the last 83 million years.
Changing frequency of geomagnetic reversals over time
The rate of reversals in the Earth’s magnetic field has varied widely over time. 72 million years ago (Ma), the field reversed 5 times in a million years. In a 4-million-year period centered on 54 Ma, there were 10 reversals; at around 42 Ma, 17 reversals took place in the span of 3 million years. In a period of 3 million years centering on 24 Ma, 13 reversals occurred. No fewer than 51 reversals occurred in a 12-million-year period, centering on 15 million years ago. Two reversals occurred during a span of 50,000 years. These eras of frequent reversals have been counterbalanced by a few “superchrons” – long periods when no reversals took place.
Statistical properties of reversals
Several studies have analyzed the statistical properties of reversals in the hope of learning something about their underlying mechanism. The discriminating power of statistical tests is limited by the small number of polarity intervals. Nevertheless, some general features are well established. In particular, the pattern of reversals is random. There is no correlation between the lengths of polarity intervals. There is no preference for either normal or reversed polarity, and no statistical difference between the distributions of these polarities. This lack of bias is also a robust prediction of dynamo theory. Finally, as mentioned above, the rate of reversals changes over time.
The randomness of the reversals is inconsistent with periodicity, but several authors have claimed to find periodicity. However, these results are probably artifacts of an analysis using sliding windows to determine reversal rates.
Most statistical models of reversals have analyzed them in terms of a Poisson process or other kinds of renewal process. A Poisson process would have, on average, a constant reversal rate, so it is common to use a non-stationary Poisson process. However, compared to a Poisson process, there is a reduced probability of reversal for some tens of thousands after a reversal. This could be due to some inhibition in the underlying mechanism, or it could just mean that some shorter polarity intervals have been missed. A random reversal pattern with inhibition can be represented by a gamma process. In 2006, a team of physicists at the University of Calabria found that the reversals also conform to a Lévy distribution, which describes stochastic processes with long-ranging correlations between events in time. The data are also consistent with a deterministic, but chaotic, process.
A superchron is a polarity interval lasting at least 10 million years. There are two well-established superchrons, the Cretaceous Normal and the Kiaman. A third candidate, the Moyero, is more controversial. The Jurassic Quiet Zone in ocean magnetic anomalies was once thought to represent a superchron, but is now attributed to other causes.
Cretaceous Normal Superchron
The Cretaceous Normal (also called the Cretaceous Superchron or C34) lasted for almost 40 million years, from about 120 to 83 million years ago, including stages of theCretaceous period from the Aptian through the Santonian. The frequency of magnetic reversals steadily decreased prior to the period, reaching its low point (no reversals) during the period. Between the Cretaceous Normal and the present, the frequency has generally increased slowly.
Kiaman Reverse Superchron
The Kiaman Reverse Superchron lasted from approximately the late Carboniferous to the late Permian, or for more than 50 million years, from around 312 to 262 million years ago. The magnetic field had reversed polarity. The name “Kiaman” derives from the Australian village of Kiama, where some of the first geological evidence of the superchron was found in 1925.
Moyero Reverse Superchron
This period in the Ordovician of more than 20 million years (485 to 463 million years ago) is suspected to host another superchron. But until now this possible superchron has only been found in the Moyero river section north of the polar circle in Siberia. Moreover, the best data from elsewhere in the world do not show evidence for this superchron.
Jurassic Quiet Zone
Certain regions of ocean floor, older than 160 Ma, have low-amplitude magnetic anomalies that are hard to interpret. They are found off the east coast of North America, the northwest coast of Africa, and the western Pacific. They were once thought to represent a superchron, but magnetic anomalies are found on land during this period. The geomagnetic field is known to have low intensity between about 130 Ma and 170 Ma, and these sections of ocean floor are especially deep, so the signal is attenuated between the floor and the surface.
Character of transitions
Most estimates for the duration of a polarity transition are between 1,000 and 10,000 years. However, geologist Scott Bogue of Occidental College and Jonathan Glen of the US Geological Survey, sampling lava flows in Battle Mountain, Nevada, found evidence for a reversal that took only four years. The reversal was dated to approximately 15 million years ago. The latest reversal, theBrunhes–Matuyama reversal, occurred approximately 780,000 years ago.
The magnetic field of the Earth, and those planets that have magnetic fields are generated by dynamo action in which convection of molten iron in the planetary core generates electric currents which in turn give rise to magnetic fields. Most scientists believe that reversals are an inherent aspect of this process. In 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. For example, Gary Glatzmaier and collaborator Paul Roberts of UCLA have made a numerical model of the electromagnetic, fluid dynamical processes of Earth’s interior. Their simulation reproduced key features of the magnetic field over more than 40,000 years of simulated time. Additionally, the computer-generated field reversed itself. During these periods, the direction and magnitude of the magnetic field observed at any point on the surface fluctuate, and net field strength is reduced by dipole-dipole interactions.
In some simulations, this leads to an instability in which the magnetic field spontaneously flips over into the opposite orientation. This scenario is supported by observations of the solar magnetic field, which undergoes spontaneous reversals every 9–12 years. However, with the sun it is observed that the solar magnetic intensity greatly increases during a reversal, whereas reversals on Earth seem to occur during periods of low field strength.
Some scientists, such as Richard A. Muller, believe that geomagnetic reversals are not spontaneous processes but rather are triggered by external events that directly disrupt the flow in the Earth’s core. Proposals include impact events or internal events such as the arrival of continental slabs carried down into the mantle by the action of plate tectonics at subduction zones or the initiation of new mantle plumes from the core-mantle boundary. Supporters of this theory hold that any of these events could lead to a large scale disruption of the dynamo, effectively turning off the geomagnetic field. Because the magnetic field is stable in either the present North-South orientation or a reversed orientation, they propose that when the field recovers from such a disruption it spontaneously chooses one state or the other, such that a recovery is seen as a reversal in about half of all cases.
Future of the geomagnetic field
 At present, the overall geomagnetic field is becoming weaker; the present strong deterioration corresponds to a 10–15% decline over the last 150 years and has accelerated in the past several years; however, geomagnetic intensity has declined almost continuously from a maximum 35% above the modern value achieved approximately 2,000 years ago. The rate of decrease and the current strength are within the normal range of variation, as shown by the record of past magnetic fields recorded in rocks (figure on right).
The nature of Earth’s magnetic field is one of heteroscedastic fluctuation. An instantaneous measurement of it, or several measurements of it across the span of decades or centuries, is not sufficient to extrapolate an overall trend in the field strength. It has gone up and down in the past with no apparent reason. Also, noting the local intensity of the dipole field (or its fluctuation) is insufficient to characterize Earth’s magnetic field as a whole, as it is not strictly a dipole field. The dipole component of Earth’s field can diminish even while the total magnetic field remains the same or increases.
The Earth’s magnetic north pole is drifting from northern Canada towards Siberia with a presently accelerating rate — 10 km per year at the beginning of the 20th century, up to 40 km per year in 2003, and since then has only accelerated. In the last decade magnetic north was shifting roughly one degree every five years.
Effects on biosphere and human society
Because the magnetic field has never been observed to reverse by humans with instrumentation, and the mechanism of field generation is not well understood, it is difficult to say what the characteristics of the magnetic field might be leading up to such a reversal.
Some speculate that a greatly diminished magnetic field during a reversal period will expose the surface of the Earth to a substantial and potentially damaging increase in cosmic radiation. However, Homo erectus and their ancestors certainly survived many previous reversals, though they did not depend on computer systems that could be damaged by large coronal mass ejections.
There is no uncontested evidence that a magnetic field reversal has ever caused any biological extinctions. A possible explanation is that thesolar wind may induce a sufficient magnetic field in the Earth’s ionosphere to shield the surface from energetic particles even in the absence of the Earth’s normal magnetic field.
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- How geomagnetic reversals are related to intensity[dead link]
- “Look down, look up, look out!”, The Economist, May 10 2007
- “Ships’ logs give clues to Earth’s magnetic decline”, New Scientist, May 11 2006
- Simple explanation of geomagnetic reversal