What Will Happen When The Earth's Magnetic Field Switches Or Collapses
So the idea that it could completely flip around, or collapse altogether, should cause us to worry, right?
Well, yes and no.
Magnetosphere Basics
The result of electrical currents generated deep within the Earth through dynamic action, the magnetosphere is a fluid force that is constantly changing in strength and orientation.
The Center of the Earth
The very heart of our planet is a solid inner core of mostly iron that is about the size of the moon.
It is so hot (9000°F to 13000°F or about 5000°C to 7200°C) that its temperature equals that of the "surface" of the sun, but it remains solid because of the combined pressure of everything above it being pulled toward it by gravity.
Surrounding this solid inner core is a second layer made primarily of an iron-nickel alloy. Nearly as hot (7200°F to 9000°F or about 4000°C to 5000°C) but under a bit less pressure, this outer core is liquid.
Around the outer core is a hot layer of dense rock, called the mantle, that "flows like asphalt under a heavy weight." At temperatures ranging from 1600°F (871°C), where it meets the Earth's crust, to 4000°F (2204°C), where it meets the outer core, it is relatively cool compared to its deeper, denser neighbors.
Electrical Currents
The disparity in temperature between the inner core and the mantle causes the Earth to become a giant magnet. As was recently explained:
These thermal movements of flowing liquid induce electrical currents that in turn create the magnetosphere:
The Magnetic Field in Flux
Given the fluidity of the system, it stands to reason that the magnetic field is not an immovable constant, but changes in its strength, orientation and polarity.
Orientation
Since it was first pinpointed in 1831 by James Ross, the magnetic north pole has moved more than 600 miles, and in recent years, this change has accelerated from "an average speed of 10 km per year . . . to 40 km per year." It is expected to move from its current location in North America to Asia within a few decades.
Waning Strength
Over the last 200 years, the magnetic field has "weakened by about 15 percent." Since the magnetic field shields the Earth's surface from some amount of radiation, "flares and coronal mass ejections from the sun," were the field to disappear entirely, there could be dramatic consequences:
Pole Reversal
Part of the natural order, over the last 20 million years, the poles have reversed, on average, every 200,000-300,000 years. However, we are long overdue for a long-term reversal, since the last one occurred about 780,000 years ago.
Although scientists aren't certain, some believe that the pole flip is related to the convection within the core, 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. Some theorize that "truly massive CMB avalanches could disrupt the geodynamo and cause Earth's dipole [two-poled magnetic] field to collapse."
Slow Reversals
Discerned from magnetic signatures found on rocks and sediments, scientists today know that the poles routinely switch places. For those reversals that last 200,000 years or more, the change occurs over a1,000 to 10,000 year-period:
Given the field's waning strength over the last couple of centuries, some scientists believe we are approaching another long-term flip. Many downplay the risk to humans, noting that the magnetosphere rarely disappears, so life on Earth remains largely protected during the reversal.
However, if the magnetic field were to significantly weaken, we could (potentially) be in trouble. In fact, some researchers have opined that there is "a direct link between the demise of the Neanderthals . . . and a significant decrease of the geomagnetic field intensity that occurred exactly at the same period."
Rapid Reversals
In recent years, scientists have found evidence that magnetic pole shifts can occur very quickly, although it is not clear if they typically result in complete reversals.
In the late 1960s near the village of Laschamp in the Massif-Central in France, scientists found incomplete evidence that led them to believe an extremely rapid, short-term magnetic reversal had occurred a mere 41,000 years ago (about the time the Neanderthal disappeared from Europe).
Other evidence of a rapid pole shift was discovered in 1995 in hardened lava in Steens Mountain, Oregon. There, magnetic crystals in the rocks indicated a super-fast magnetic shift had occurred, one in which the poles moved "over 10,000 times faster than normal, at six degrees a day."
At that breakneck rate, a complete magnetic shift could occur in months, rather than thousands of years, so many scientists were understandably skeptical - that is until further evidence of short-term flips was found in 2010 in Battle Mountain, Nevada, where it was revealed that the "magnetic field moved by 53 degrees in a single year."
Even more recently, in 2012, scientists re-visited the Laschamp event, this time examining sediment cores from the Black Sea as well as other data from the South Pacific and North Atlantic, and their findings were remarkable:
Although there is no direct evidence of a causal relationship, the Black Sea sediment cores also revealed that two other "extreme scenarios" occurred at about the same time:
Want to gain some daily interesting knowledge? Today I Found Out offers a free daily newsletter to help you feed your brain.