ScienceDaily (Sep. 26, 2008) -- Earth's north magnetic pole is shifting and weakening. Ancient lava flows are guiding a better understanding of what generates and controls the Earth's magnetic field -- and what may drive it to occasionally reverse direction.
The main magnetic field, generated by turbulent currents within the deep mass of molten iron of the Earth's outer core, periodically flips its direction, such that a compass needle would point south rather than north. Such polarity reversals have occurred hundreds of times at irregular intervals throughout the planet's history -- most recently about 780,000 years ago -- but scientists are still trying to understand how and why.
Short of a complete polar reversal (North moving to South) the poles have "wandered" significantly over the last 80,000 years. These changes puzzle scientists because the corresponding changes to the equator should have dramatically effected the Earth's climate. Below are some examples of the equator at verious times in our recent past history.|
63 degrees N, 135 degrees W. From the Yukon area of North America at about
80,000 B.P.(before present era) and moving east by 75,000 B.P
to the Greenland Sea.
72 degrees N, 10 degrees E. From the Greenland Sea, starting at about
55,000 B.P. and then moving south-west by 50,000 B.P.
what is now Hudson Bay.
60 degrees N, 73 degrees W. From the Hudson Bay area at about 17,000 B.P. and moving north to its present location by about 12,000
The current position. When and where will the next shift occur?
For more information on why the poles may have shifted see Changing Poles on viewzone.com.
A new study of ancient volcanic rocks, reported in the Sept. 26 issue of the journal Science
, shows that a second magnetic field source may help determine how and whether the main field reverses direction. This second field, which may originate in the shallow core just below the rocky mantle layer of the Earth, becomes important when the main north-south field weakens, as it does prior to reversing, says Brad Singer, a geology professor at the University of Wisconsin-Madison.
Singer teamed up with paleomagnetist Kenneth Hoffman, who has been researching field reversals for over 30 years, to analyze ancient lava flows from Tahiti and western Germany in order to study past patterns of the Earth's magnetic field. The magnetism of iron-rich minerals in molten lava orients along the prevailing field, then becomes locked into place as the lava cools and hardens.
According to Singer:
"When the lava flows erupt and cool in the Earth's magnetic field, they acquire a memory of the magnetic field at that time... It's very difficult to destroy that in a lava flow once it's formed. You then have a recording of what the paleofield direction was like on Earth."
Hoffman (California Polytechnic State University at San Luis Obispo and UW-Madison), and Singer are focusing on rocks that contain evidence of times that the main north-south field has weakened, which is one sign that the polarity may flip direction. By carefully determining the ages of these lava flows, they have mapped out the shallow core field during multiple "reversal attempts" when the main field has weakened during the past million years.
During those periods of time, weakening of the main field reveals "virtual poles," regions of strong magnetism within the shallow core field. For example, Singer says, "If you were on Tahiti when those eruptions were taking place, your compass needle would point to not the North Pole, not the South Pole, but Australia."
The scientists believe the shallow core field may play a role in determining whether the main field polarity flips while weakened or whether it recovers its strength without reversing. "Mapping this field during transitional states may hold the key to understanding what happens in Earth's core when the field weakens to a point where it can actually reverse," Hoffman says.
Current evidence suggests we are now approaching one of these transitional states because the main magnetic field is relatively weak and rapidly decreasing, he says. While the last polarity reversal occurred several hundred thousand years ago, the next might come within only a few thousand years.
According to Singer:
"Right now, historic records show that the strength of the magnetic field is declining very rapidly. From a quick back-of-the-envelope prediction, in 1,500 years the field will be as weak as it's ever been and we could go into a state of polarity reversal... One broad goal of our research is to provide some predictive capability for what could happen and what could be the signs of the next reversal."
Movement Of Earth's North Magnetic Pole Accelerating Rapidly
After some 400 years of relative stability, Earth's North Magnetic Pole has moved nearly 1,100 kilometers out into the Arctic Ocean during the last century and at its present rate could move from northern Canada to Siberia within the next half-century.
If that happens, Alaska may be in danger of losing one of its most stunning natural phenomena - the Northern Lights.
But the surprisingly rapid movement of the magnetic pole doesn't necessarily mean that our planet is going through a large-scale change that would result in the reversal of the Earth's magnetic field, Oregon State University paleomagnetist Joseph Stoner reported today at the annual meeting of the American Geophysical Union in San Francisco, Calif.
"This may be part of a normal oscillation and it will eventually migrate back toward Canada," said Stoner, an assistant professor in OSU's College of Oceanic and Atmospheric Sciences. "There is a lot of variability in its movement."
Calculations of the North Magnetic Pole's location from historical records goes back only about 400 years, while polar observations trace back to John Ross in 1838 at the west coast of Boothia Peninsula. To track its history beyond that, scientists have to dig into the Earth to look for clues.
Stoner and his colleagues have examined the sediment record from several Arctic lakes. These sediments -- magnetic particles called magnetite -- record the Earth's magnetic field at the time they were deposited. Using carbon dating and other technologies -- including layer counting -- the scientists can determine approximately when the sediments were deposited and track changes in the magnetic field.
The Earth last went through a magnetic reversal some 780,000 years ago. These episodic reversals, in which south becomes north and vice versa, take thousands of years and are the result of complex changes in the Earth's outer core. Liquid iron within the core generates the magnetic field that blankets the planet.
Because of that field, a compass reading of north in Oregon will be approximately 17 degrees east from "true geographic north." In Florida, farther away and more in line with the poles, the declination is only 4-5 degrees west.
The Northern Lights, which are triggered by the sun and fixed in position by the magnetic field, drift with the movement of the North Magnetic Pole and may soon be visible in more southerly parts of Siberia and Europe -- and less so in northern Canada and Alaska.
In their research, funded by the National Science Foundation, Stoner and his colleagues took core samples from several lakes, but focused on Sawtooth Lake and Murray Lake on Ellesmere Island in the Canadian Arctic. These lakes, about 40 to 80 meters deep, are covered by 2-3 meters of ice. The researchers drill through the ice, extend their corer down through the water, and retrieve sediment cores about five meters deep from the bottom of the lakes.
The 5-meter core samples provide sediments deposited up to about 5,000 years ago. Below that is bedrock, scoured clean by ice about 7,000 to 8,000 years ago.
"The conditions there give us nice age control," Stoner said. "One of the problems with tracking the movement of the North Magnetic Pole has been tying the changes in the magnetic field to time. There just hasn't been very good time constraint. But these sediments provide a reliable and reasonably tight timeline, having consistently been laid down at the rate of about one millimeter a year in annual layers.
"We're trying to get the chronology down to a decadal scale or better."
What their research has told Stoner and his colleagues is that the North Magnetic Pole has moved all over the place over the last few thousand years. In general, it moves back and forth between northern Canada and Siberia. But it also can veer sideways.
"There is a lot of variability in the polar motion," Stoner pointed out, "but it isn't something that occurs often. There appears to be a 'jerk' of the magnetic field that takes place every 500 years or so. The bottom line is that geomagnetic changes can be a lot more abrupt than we ever thought."
Shifts in the North Magnetic Pole are of interest beyond the scientific community. Radiation influx is associated with the magnetic field, and charged particles streaming down through the atmosphere can affect airplane flights and telecommunications.
[ScienceDaily (Dec. 9, 2005)]
Displacement of EarthÕs magnetic poles may turn planet into giant Hiroshima
The planet's magnetic poles are being displaced. Scientists say that mankind may eventually find itself defenseless against the cosmic radiation, and the Earth will turn into the giant Hiroshima.
The chief scientist of the Central Military Institute for Ground Troops, Candidate of Technical Sciences, Yevgeni Shalamberidze, that that the geographic poles of the planet remain on their previous positions, whereas the magnetic poles have already drifted away 200 kilometers each. This phenomenon affects the processes of global scale.
"The planet relieves its excessive energy into space through crust fractures. When those breakouts close, the negative energy is left on the planet. It is not ruled out that the growing number of catastrophes that rocked the world during the recent years is based on the displacement of the magnetic poles," the scientist said.
Alexander Fefelov, a senior spokesman for the Russian Academy of Natural Sciences, said that planet Earth would have its magnetic and geographic poles relocated during the upcoming years.
"Planet Earth on the orbit is a round object in weightlessness. The planet may suddenly change its axial inclination from time to time. It happens once in 23,000 years. The pole displacement angle may reach 30 degrees. The South Pole used to be located in the area of Easter Island before the latest displacement, whereas the North Pole was located in the Himalayas. That is why mammoths, rhinoceroses and saber-toothed tigers used to inhabit Arctic latitudes. It was a very sudden displacement of poles. Archeologists still uncover animals with indigested herbal food in their stomachs, which means that the animals died as a result of fast freezing, so to speak," the scientist said.
The displacement of poles can result in the disappearance of the atmosphere, which in its turn will cool the planet to 273 degrees below zero Centigrade. The biosphere of the planet will virtually be killed in this case; only those located close to the EarthÕs axis will survive the disaster.
Doctor of Physical and Mathematic Sciences, Vladimir Kuznetsov, said that planet Earth had experienced 16 polar displacements in 4 million years. "There is no chance that the EarthÕs magnetic field will disappear. The planet will always have the radiation shield. Even a possible change of the poles will not be able to make the magnetic field vanish. The planet will not be frozen. The geomagnetic field does change, but it is not dangerous. Even if the poles drift hundreds of kilometers away, there will be no threat to humanity posed."
Viewzone || Comments?
I guess the first thing that will freak people is when the GPS units in their cars don't work. Also I think airplanes use the same system to navigate -- ships also. So it's going to be a big mess when it happens.