 Earth's Inconstant Magnetic Field
Our planet's magnetic field is in a constant state of change, say researchers who are beginning to understand how it behaves and why.
Every few years, scientist Larry Newitt of the Geological Survey of Canada goes hunting. He grabs his gloves, parka, a fancy compass, hops on a plane and flies out over the Canadian arctic. Not much stirs among the scattered islands and sea ice, but Newitt's prey is there--always moving, shifting, elusive.
His quarry is Earth's north magnetic pole.
At the moment it's located in northern Canada, about 600 km from the nearest town: Resolute Bay, population 300, where a popular T-shirt reads "Resolute Bay isn't the end of the world, but you can see it from here." Newitt stops there for snacks and supplies--and refuge when the weather gets bad. "Which is often," he says.
Right: The movement of Earth's north magnetic pole across the Canadian arctic, 1831--2001. Credit: Geological Survey of Canada. [More]
Scientists have long known that the magnetic pole moves. James Ross located the pole for the first time in 1831 after an exhausting arctic journey during which his ship got stuck in the ice for four years. No one returned until the next century. In 1904, Roald Amundsen found the pole again and discovered that it had moved--at least 50 km since the days of Ross.
The pole kept going during the 20th century, north at an average speed of 10 km per year, lately accelerating "to 40 km per year," says Newitt. At this rate it will exit North America and reach Siberia in a few decades.
Keeping track of the north magnetic pole is Newitt's job. "We usually go out and check its location once every few years," he says. "We'll have to make more trips now that it is moving so quickly."
Earth's magnetic field is changing in other ways, too: Compass needles in Africa, for instance, are drifting about 1 degree per decade. And globally the magnetic field has weakened 10% since the 19th century. When this was mentioned by researchers at a recent meeting of the American Geophysical Union, many newspapers carried the story. A typical headline: "Is Earth's magnetic field collapsing?"
Probably not. As remarkable as these changes sound, "they're mild compared to what Earth's magnetic field has done in the past," says University of California professor Gary Glatzmaier.
Sometimes the field completely flips. The north and the south poles swap places. Such reversals, recorded in the magnetism of ancient rocks, are unpredictable. They come at irregular intervals averaging about 300,000 years; the last one was 780,000 years ago. Are we overdue for another? No one knows.
Above: Magnetic stripes around mid-ocean ridges reveal the history of Earth's magnetic field for millions of years. The study of Earth's past magnetism is called paleomagnetism. Image credit: USGS. [More]
According to Glatzmaier, the ongoing 10% decline doesn't mean that a reversal is imminent. "The field is increasing or decreasing all the time," he says. "We know this from studies of the paleomagnetic record." Earth's present-day magnetic field is, in fact, much stronger than normal. The dipole moment, a measure of the intensity of the magnetic field, is now 8 x 1022 amps x m2. That's twice the million-year average of 4 x 1022 amps x m2.
To understand what's happening, says Glatzmaier, we have to take a trip ... to the center of the Earth where the magnetic field is produced.
At the heart of our planet lies a solid iron ball, about as hot as the surface of the sun. Researchers call it "the inner core." It's really a world within a world. The inner core is 70% as wide as the moon. It spins at its own rate, as much as 0.2o of longitude per year faster than the Earth above it, and it has its own ocean: a very deep layer of liquid iron known as "the outer core."
Right: a schematic diagram of Earth's interior. The outer core is the source of the geomagnetic field. [Larger image]
Earth's magnetic field comes from this ocean of iron, which is an electrically conducting fluid in constant motion. Sitting atop the hot inner core, the liquid outer core seethes and roils like water in a pan on a hot stove. The outer core also has "hurricanes"--whirlpools powered by the Coriolis forces of Earth's rotation. These complex motions generate our planet's magnetism through a process called the dynamo effect.
Using the equations of magnetohydrodynamics, a branch of physics dealing with conducting fluids and magnetic fields, Glatzmaier and colleague Paul Roberts have created a supercomputer model of Earth's interior. Their software heats the inner core, stirs the metallic ocean above it, then calculates the resulting magnetic field. They run their code for hundreds of thousands of simulated years and watch what happens.
What they see mimics the real Earth: The magnetic field waxes and wanes, poles drift and, occasionally, flip. Change is normal, they've learned. And no wonder. The source of the field, the outer core, is itself seething, swirling, turbulent. "It's chaotic down there," notes Glatzmaier. The changes we detect on our planet's surface are a sign of that inner chaos.
They've also learned what happens during a magnetic flip. Reversals take a few thousand years to complete, and during that time--contrary to popular belief--the magnetic field does not vanish. "It just gets more complicated," says Glatzmaier. Magnetic lines of force near Earth's surface become twisted and tangled, and magnetic poles pop up in unaccustomed places. A south magnetic pole might emerge over Africa, for instance, or a north pole over Tahiti. Weird. But it's still a planetary magnetic field, and it still protects us from space radiation and solar storms.
Above: Supercomputer models of Earth's magnetic field. On the left is a normal dipolar magnetic field, typical of the long years between polarity reversals. On the right is the sort of complicated magnetic field Earth has during the upheaval of a reversal. [More]
And, as a bonus, Tahiti could be a great place to see the Northern Lights. In such a time, Larry Newitt's job would be different. Instead of shivering in Resolute Bay, he could enjoy the warm South Pacific, hopping from island to island, hunting for magnetic poles while auroras danced overhead.
Sometimes, maybe, a little change can be a good thing.
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 Polar Shift by 2012?
New Evidence and Theory Suggests Einstein May Have Been Right
By Carl Peterson
Science has long speculated that the earth's center rotates at a different speed from the crust. The big question really has been "What holds the earth's crust in equilibrium with the center?" Visionary writer and inventor Carl Peterson may have discovered the answer. In looking for the reasons "magnetic north" lies far from the North Pole, Peterson has stumbled upon a scientific explanation that also fits with past polar shifts; and offers probable causes, timing, and local effects of the next shift. His theory complements and completes a Charles Hapgood theory endorsed by Albert Einstein, in which the poles, aided by massive ice build up, are eventually thrown by centrifugal force to the equator.
If the center rotates at a different speed from the crust, there is good reason to believe that this is the cause for the static electricity apparent on the earth's surface. If that is true, then North Pole on the crust must have an opposite magnetic charge from north in the earth's core.
Are the Earth's poles shifting in 2012?
by Nicholas Gerbis
Pole shift refers to a geological phenomena in which the Earth's outermost layers move together as one piece.
Image © HowStuffWorks.com
Some say the world will end in fire; some say ice. Lately, screenwriters and apocalypse enthusiasts have preferred natural cataclysms as their world-killers. As for when the end will arrive, those folks who claim to be in the know have an affinity for stamping 2012 as the Earth's sell-by date.
Why 2012? The answer traces back to true believers' interpretations (and reinterpretations) of Nostradamus, Edgar Cayce and various other ambiguous and nonscientific sources. Some armchair eschatologists have narrowed the expiration date further, to Dec. 21, 2012 -- when, they argue, the Mayan Long Count calendar ends its 5,125-year cycle. However, experts agree that the Mayans themselves did not believe that the world would end on this date, so feel free to buy green bananas on Dec. 19, 2012 [source:MacDonald].
The lack of scientific evidence for the coming apocalypse hasn't deterred believers from trotting out scientific theories to serve as evidence of imminent mass destruction. One of the most remarkable ideas they've chosen to flog is the pole shifthypothesis, in which the Earth's crust and mantle (or outermost layers) move as one piece. Pole shift might send the poles sliding toward the equator, swing North America poleward or produce any arrangement that might result from turning a globe in your hands.
People have been batting around some version of the pole shift hypothesis since at least the mid-19th century and, although many of the scientific questions it attempted to answer have since been addressed by plate tectonics, it's rooted solidly in physics. Plate tectonics and pole shifts interact and are governed by the same forces, but pole shifts, in which the outer shell of the world moves as one piece, produce very different results than plate tectonics, in which pieces of the Earth's crust bump, grind and slide -- opening seas, building mountain ranges and rearranging continents.
If a large pole shift could happen suddenly, the redistribution of land and water it caused would be nothing short of cataclysmic. In the short term, it would mean earthquakes, strange weather patterns, massive tsunamis capable of drowning parts of continents, and possibly gaps in the planet's magnetic field -- our shield against harmful cosmic rays. In the long term, the redistribution of land and water in the tropics, subtropics and poles would fundamentally alter ocean currents and the heat balance of the Earth, resulting in widespread climatological shifts. Ice caps might melt and reform elsewhere, or remain melted, driving sea levels down or up.
All of which returns us to the question: Could such a catastrophic shift occur, and if so, will it happen in 2012? We'll tell you next -- if the world doesn't end before you click to the next page.
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