Pole reversal: Feared "flip" of Earth's magnetic field takes 7,000 years

PARIS (AFP) - A reversal of the Earth's magnetic field, a rare but feared event due to the catastrophic effect it could have on human life, takes about 7,000 years to complete, according to a study.

The so-called "flip" between the Earth's North and South poles occurs at long but unpredictable intervals, the most recent one occurring about 780,000 years ago.

The 180-degree switch occurs when there is a change in the circulation patterns in the molten iron which flows around the Earth's outer core and, like a dynamo, creates the magnetic field.

The intensity of the field drops for a while before the circulation rhythm is established and the new polarity occurs.
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http://story.news.yahoo.com/news?tmpl=story&cid=1540&e=14&u=/afp/science_magnetism

and it will flip just before the election and all those negativly charged Neo-Cons will get sent hurdling into deep space! We can only hope!

"The intensity of the field drops for a while before the circulation rhythm is established and the new polarity occurs."

:freak:

>is this being caused by global warming?

No.

In fact, it's probably not happening at all. Evidence is scarce - not enough to form a conclusion either way.

at all?

just where does all the heat come from? gravity? radioactive potassium? some magical mechanism of concentrating solar energy?

(yeah, i know i could go look this up on my own . . . )

Once upon a time, the earth was a hot molten ball of gas or what have you and as it cooled off, then the heavier elements (some radioactive) sank to the center because of gravity and a light crust floated to the surface and began to cool. Radioactive heating has kept the center of the earth from completely solidifying ever since.

Here is an article about it if you want to learn more. I feel like my brief answer is so over-simplified as to almost be false but maybe it will give you a vague idea:

http://www.nature.com/nsu/030505/030505-5.html

so the radioactive phosphorus decay is correct (i had heard that before but didn't take it seriously - that must be a hell of a lot of phosphorus).

anyhow, based on a half-life of 1.25 billion years, there must only be 1/7th or 1/8th the original amount of K-40 left - i guess that would explain the slow solidification of the core the article mentioned. looks like we're all doomed in the next few billion years - just what we need, more bad news!

It's actually hotter than the surrounding liquid core. It's solid because the pressure is so much higher.

There is a lot of Uranium and Plutonium on Earth. 99% of it is in the core though. The heat of radiation has kept the core of the Earth hot for 4.5 billion years.

Almost all of it is Plutonium-244 found (on an atomic level) in old Thorium ores in California. The amount of it is so small, that it is literally confined to a few atoms. Plutonium-244 (half-life 80 million years) was probably found in fair quantities on earth for several hundred million years after it's formation, although all of it effectively has now decayed to radioactive Thorium-232. Tiny, although largely undectable, amounts of Plutonium-239 are formed from the neutron fluxes that occur in natural Uranium ores. About 1.8 billion years ago, neutron fluxes in Uranium ores were so high that naturally occurring nuclear reactors, about 15 of them, ran for hundreds of thousands of years in a place called Oklo, Gabon. These undoubtably generated considerable heat, but the decay of Uranium-235 over hundreds of millions of years now makes naturally occuring nuclear reactors impossible.

The internal heat of the earth today derives from five radioactive decay chains. One is that Uranium-238 and all of its daughters (Thorium-234, Protactinium-234, Uranium-234, Thorium-230, Radon-226, Radon-222, Polonium-218, lead-214, Bismuth 214, Polonium-214, Lead-210, Bismuth-210, Polonium-210). The latter decays to stable lead 206. For Thorium-232 the decay chain is similar. The Uranium-235 decay chain is more complex and includes all of the above elements plus tiny fractions of the extremely radioactive elements Actinium and Francium. Two other elements contribute heat, potassium-40, (which is the primary source of natural physiological radioactivity found in all living tissue) and Rubidium-87. The majority of the potassium-40 found on the earth at the time of its formation has now decayed to Argon, where it constitutes a significant portion of the atmosphere. The remaining potassium-40 is still a relatively important source of the internal heat of the earth, though not nearly as important as the Uranium and Thorium decay chains. Rubidium-87 generates an almost insignificant portion of the heat, but it is a fair constituent of the radioactivity of natural tissues. (Rubidium mimics potassium very closely in its chemistry and is present in all living tissue, though it has no known physiological purpose.)

Some radioactive elements are also formed constantly in earth's atmosphere. The most famous is Carbon-14, which is formed in the upper atmosphere as a result of nuclear reactions deriving from interaction with high energy solar particles with Nitrogen. In this reaction, neutrons produced by the sun or by the interaction of cosmic rays and atmospheric atoms ("spallation" reactions) hit Nitrogen-14 causing it to eject a proton (a hydrogen ion). The rate of formation and decay of carbon-14 has long been at equilibrium, it decays as fast as it is formed, and this equilibrium establishes the atomic clock in radiocarbon dating.

Another radioactive element formed in the upper atmosphere in measurable quantities is Krypton-85. Naturally occuring Krypton-84 in the atmosphere is hit by neutrons (from the same source as with carbon-14) and transformed into Krypton-85. The majority of the Krypton-85 found on earth today, however derives from nuclear testing and nuclear power plants. (Krypton-85 is the only normal radioactive release of nuclear power plants.)

About 18 grams of radioactive tritium, a form of hydrogen, is produced each year from interaction of solar neutrons with deuterium that is naturally found in water.

Radioactive phosphorus does not naturally occur on earth. All that is present in the environment is the result of leaks from laboratories (where it is an important tracer in biochemical studies, particularly of DNA).

geothermal energy is really a form of nuclear energy?

btw, for those (like myself) who know next to nothing about geothermal energy, a fairly interesting and moderately informative slideshow can be found at:

http://geothermal.marin.org/GEOpresentation/sld001.htm

when you consider it's physical origins. The overwhelming majority of it, is not derived from neutron induced fission, but comes from ordinary nuclear decay. (Caveat: Some people consider alpha decay fission, albeit highly controlled fission, since it results in two new atoms, one of which is always helium.)

Only one form of energy on earth does not have, as it's ultimate source, energy that originated in nuclear interactions. (This remark is made in ignorance of a successful GUT or Grand Unification Theory). This is tidal energy, which derives from gravatational interactions as opposed to nuclear interactions.

Nuclear decay heat type devices, as opposed to fission devices, are sometimes manufactured for technological purposes. Usually the devices are spacecraft which use the decay heat of Plutonium-238 to power them. The Pioneer, Voyager, Cassini, Galileo, and the Apollo seismographs all used Plutonium-238. (Apollo 13's seismograph crashed back into the earth when that mission was abandoned as shown in the movie.) Other types of devices that have used plutonium-238 decay heat include pacemakers.

So called nuclear "waste" also has decay heat. There have been many proposals to use Strontium-90, a pure beta emmitter (no penetrating radiation), to provide batteries that would work for many decades without recharging. The technological application is limited by two things. One of course is the old standby, irrational public fear of anything radioactive. The other limitation is more interesting. There is a maximal amount of strontium-90 that can accumulate, after which it is impossible to add more. This is because it decays at the same time as it is created and ultimately equilibrates. This means that if an amount of energy equal to that of the entire world output of energy in 2050, 1000 exajoules, was created from nuclear energy, it would be possible to accumulate (over about 150 years) about 11,000 MT of Strontium-90. Once you'd accumulated this amount, the Strontium-90 would be decaying about as quickly as it is formed. Strontium-90 (in equilibrium with Y-90 in its decay chain to Zr-90) puts out about 1 watt per gram. This means each metric ton puts out a megawatt. Thus the total amount of Strontium 90 it is possible to accumulate would be putting out about 11,000 MWth, the energy of 3 additional fission nuclear plants.

These plants would have nearly the same risk as any geothermal plant but would be transportable to any place on earth. (They need not be the size of a standard nuclear plant, 3000 MWth, of course; the total number of reactors would be the total energy output of accumulated Sr-90 divided by the power or each plant.) Their side product would be isotopically and chemically (Hafnium free) pure Zr-90, a non-radioactive metal which is very valuable where refractory corrosion resistant metal is required. At equilibrium, these plants would produce about 275 metric tons of pure zirconium metal per year.

Pole reversals are sound science. We have very good evidence from studies of the floor of the Atlantic Ocean to prove that they occur at irregular intervals over geological time.

What we don't have, possibly can't have, is a way to predict when the poles will reverse again. As it isn't likely to happen during the presumably brief future (in geological time scales) of the human race, and there wouldn't be anything we could do to stop it anyway, there is a limit to how much time and energy serious geologists are prepared to spend worrying about it.

You are absolutely correct to point out pole reversals have nothing to do with our current problems of global warming/climate change.

Unless you're really using a standard magnetic compass, it wouldn't have much of an impact on regular human events.

and the evidence for it is in the geologic record. Computer models have also compliled all the known flips and ran a model and guess what..sudenly things went crazy and the poles fliped!

You forget about the most important thing,our magnetic field sheilds the planet from the intense solar radiation. If the field becomes unstable and flips, our protective shield will also fluctuat. This could allow massive amounts of Gamma radiation (and others) to penetrate the sheild and escentialy microwave any lifeform unlucky enough to be in the effected area.

I'd like mine well done please!

If they did, there would be nothing left on Earth. The flips have happened literally thousands of times since the Triassic (the oldest rocks that record the flips), and the periods with no field last between hundreds to thousands of years. There are no extinctions recorded to be coincident with magnetic field flips, so I think that the danger is really overblown.

I never doubted their reality, I just was saying that unless your survival depends on a magnetic compass, you don't have anything to worry about.

extinctions. I was merly suggesting that the radiation that would get through would cause a lot of damage to life. Cancers, illness and assorted afflictions. And forgive me about what radiation would get through..i'm no rocket scientist, but harmfule radiation would get closer than it normally would. And it would have adverse effects on anything that got a good dose.