Mapped by satellites, it's a giant pothole in the magnetic field off the coast of Brazil. Geophysicists believe the problem is the South Atlantic Anomaly. So you could never build a tunnel through its diameter. On the other hand, 'the field could turn and start growing again.' 1The Earth is largely solid or molten liquefied by heat 1 rock thats hot enough to melt iron.

The most recent reversal occurred about 750,000 years ago - three times the average interval. The latest weakening is consistent with the start of a new pole reversal, Olson said. But 'no one has been able to establish a convincing correlation,' Olson said. Paleontologists have tried to match pole reversals with great extinctions evident in the fossil record. But intervals have ranged from thousands of years to millions. Over the past 5 million years, Olson said, it's averaged once every 250,000 years. Geophysicists can read the timing, strength and direction of those ancient magnetic fields in old lava and sedimentary rock.īy one count, 171 pole reversals have occurred in the past 71 million years. It occurs with intermittent reversals in the direction of the field, when Earth's magnetic poles swap positions - north to south, south to north. But it has always maintained at least 10 percent of its current strength, and the hazard has always been brief, a few thousand years. The Earth's geomagnetic field has weakened substantially many times in the past 3 billion years, Olson said. Some say the atmosphere itself might erode, and the planet would eventually become uninhabitable. Radiation injuries and genetic mutations would mount. 'You wouldn't see it, but you would be exposed to more radiation,' Olson said. If the field shut down today, solar particles and radiation would stream into the atmosphere, creating worldwide auroras of a kind now seen only near the poles.

In real life, the loss of the Earth's magnetic field would have more gradual effects, from the curious to the catastrophic. It's all based on a particle of truth, Olson said, 'but they took the actual phenomena as we currently understand them and exaggerated everything.' Lightning bolts blast the Colosseum to rubble. Increased radiation from space and electrical changes in the atmosphere stop watches and melt suspension cables on the Golden Gate Bridge like an overloaded fuse.

Molton core tunnel