Scientists claim that the earth’s magnetic poles will reverse within a few thousand years. So why does that happen? The north and south poles weren’t always that way. About 786,000 years ago, the earth’s magnetic field reversed and remained constant. But before that happened, the south was north.
According to scientists, the earth’s dipole magnetic field starts to weaken every half million years before reversing completely. It’s thought to be caused by changes in the fluid portion of the earth’s iron core. About 20 million years ago, the Earth’s magnetic field reversed about once every 200,000 to 300,000 years. This is called a geomagnetic reversal. Recent research shows that the Earth’s magnetic field is weakening ten times faster.
It is about 5 percent per decade, a sign that the magnetic field may be starting the process of reversing. There isn’t any evidence suggesting that magnetic field reversals have led to mass extinctions in the past.
What happens when earth’s magnetic field reverses?
The direction of the magnetic field depends on the direction of the giant electrical currents, which depend on the direction of small magnetic loops. The helical convection flows generate it. If the magnetic field were switched off entirely, it would reestablish itself randomly, with the north and south magnetic poles aligned either way or the other.
There seems to be no pattern in the geological record when the field flips, nor which alignment is preferred. So that’s probably how the reverse happens. Earth’s magnetic field isn’t necessarily switched off. But it’s scrambled in some way. It then builds up again, choosing its direction randomly.
- When it does a full reverse, it creates a geomagnetic reversal.
- When the field glitches but ends in the same direction, it starts a geomagnetic excursion.
Here’s what happens during a magnetic field reversal:
Weakening and Variation of Magnetic Field: As the reversal process begins, the strength of the Earth’s magnetic field weakens. The magnetic field becomes more complex, with multiple poles and areas of magnetic variation across the globe.
Navigation and Animal Behavior: The shifting and weakening of the magnetic field can affect navigation systems that rely on magnetic compasses, such as those used by migratory birds, sea turtles, and certain marine species. During a reversal, these organisms may need to adapt their navigation strategies.
Solar Radiation: During a reversal, the Earth’s magnetic field may be temporarily weakened, which can result in increased exposure to solar radiation. However, the planet’s atmosphere and other layers of protection, such as the ozone layer, still shield us from most harmful radiation.
Impact on Technology: Reversals can impact technology and electrical systems. The changing magnetic field can induce fluctuations in power grids, disrupt satellite communications, and affect sensitive electronic equipment. However, modern technology and infrastructure are designed to handle such variations and can be shielded or adjusted accordingly.
Geologic Record: The magnetic field reversal is recorded in rocks through a phenomenon known as magnetic stratigraphy. As molten lava or sediment solidifies, it aligns with the current magnetic field. The newly formed rock will show the opposite magnetic orientation when the field reverses. This record in rocks provides valuable evidence for studying the history of magnetic field reversals.
Effects on Earth’s surface
There are a few ideas on how these glitches might happen. It may be that some event triggers a disruption in the flows within the outer core. It could be an asteroid or comet impact, an interaction between the core and mantle.
Scientists presumed this reversal process took a few thousand years. But new evidence suggests that the most recent major reversal 786,000 years ago happened in less than 100 years, roughly a single lifetime. Flips like this have occurred several times throughout Earth’s history.
Scientists say the next one may happen within the next few thousand years. New evidence indicates that the Earth’s magnetic field intensity is decreasing at a rate ten times faster than normal. It leads many geophysicists to believe we’re on the brink of another reversal. So what would happen if that did occur? Would there be any noticeable changes? The good news is there are no documented catastrophes associated with past reversals.
The Earth has had a magnetic field for millions of years. It protects from radiation from space and coronal mass ejections from the Sun. A magnetic reversal would almost surely wreak havoc on our electrical grid. It could potentially bring it down. Also, It would make it vulnerable to energetic particles from the Sun and cosmic rays, which can cause genetic mutations. That could happen before the reversal even takes place.
Our navigational equipment would get disoriented, and compasses would point to the wrong part of the world. The blow on the animal kingdom could be much worse, depending on how slowly it reverses.
- If it moves too fast, this could cause mass extinctions of thousands of species that rely on the magnetic field to find their migration or spawning grounds.
If the magnetic field weakens, there is still an atmosphere to protect from harmful radiation. The main concern is that power grids and communications systems may be at risk. Also, animals that use the magnetic field to navigate might be confused. Research suggests that many rely on the magnetic field to find their way. Birds migrate by following a specific field gradient.
Homing pigeons find their way home by using the magnetic field. It is theorized that many migrating fish, like salmon, use the magnetic field to find their way. Some predators, like foxes, prefer to attack from a North-Eastern direction, and large grazing animals tend to align north-south while grazing. Any animal using the magnetic field for navigation would surely get lost and die.
There’s a period before reversals where the magnetic field gets progressively weaker. The genetic mutations that arise from that could potentially increase cancer rates. So the longer it takes for that reversal process to complete, the more harmful it will be to us.
Humanities would move underground and start a new civilization there, with thick rock layers protecting us from radiation. Going to the surface would only be possible briefly, and a special suit would probably be needed.
The magnetic field has weakened by over 20% this century at the ‘South Atlantic Anomaly.’ Half its area has grown over three times to a massive 105 million square km. It equals roughly 70% of the world’s landmass and about one-fifth of the Earth’s surface. The magnetic field in this area is so weak that many satellites suffer problems when flying over it.
Their systems malfunction, they lose communication, and some break altogether. When flying through this zone, the Hubble space telescope stops observing and shuts down sensitive equipment. NASA astronauts have reported seeing many ‘shooting stars’ when passing the region, which are cosmic particles hitting their retinas. It has also been reported that a flyby through this region once fried several modern laptops on the International Space Station.
Suppose the field’s weakening in this region continues. In that case, it might become impossible to fly airplanes through it—the risk of failing electronics and a higher risk of cancer for the passengers and airplane staff. Satellites could stop working entirely in this region, severely crippling their technology. If the region grows large enough, it can influence our global network.
The anomaly is mostly above the ocean but already over much of South America and Africa. However, at the rate that this anomaly is growing, it will envelop the United States in roughly 100 years. The field will have weakened by another 15%.
The entire world will be enveloped in roughly 350 years, by which time the field will have only 50% of the strength of today. A small consolidation is that we would regularly see auroras at all latitudes. History shows that during a polar reversal, many things can happen.
- There are also recorded cases of the magnetic poles breaking up into 4, 6, and even 8 due to instabilities in the Earth’s core.
These fields will be much weaker than the current one and point in random directions. The fields will be very messy and much less capable of defending themselves from the harsh conditions of space. For this reason, studying the Earth’s magnetic field and predicting what will happen is very important.
The forerunners of this are the European Space Agency with its Swarm satellites. These spacecraft form a constellation and have scanned the Earth for over 6 years, making very accurate maps of the Earth’s magnetic field. Knowing how and when the field changes will allow us to predict the required level of satellite protection and plan to minimize this influence on the planet.
What causes a magnetic field?
Magnetic fields are generated in two ways: In magnetic materials like iron, the small magnetic fields of their constituent particles align to give a global field. Alternatively, flows of many charged particles like electrons can produce magnetic fields, for example, in an electromagnet. But Earth’s interior is not intrinsically magnetic. It’s too hot for the iron atoms in the core to align spontaneously.
Although the interior is rotating, it’s electrically neutral, So there shouldn’t be an overall electrical current. Earth’s core lies beneath the thin crust and 2900 km of solid mantle. The 2400 km thick outer core is molten iron, nickel, and other stuff. Beneath this layer is the inner core, a 1200 km radius ball of solid iron. It’s solid because of the around 5500 Kelvin temperature pressure at that depth. It would instantly melt at lower pressures.
The outer core has a rotation gradient. The outer layer rotates a bit slower than the surface. But it speeds up deeper, and that motion gets messier. As the inner core grows, it releases non-iron impurities that flow upwards, joining convection streams. These flows are then twisted into helixes by the Coriolis force, the same effect that produces hurricanes on Earth’s surface. It’s all of this motion that together makes Earth’s magnetic field through a process.
The Earth has a magnetic field due to the molten iron in the outer core. The motion of that molten iron and some complicated physics generate a magnetic field through the dynamo effect. Therefore, the molten iron’s motion must change to reverse the magnetic field. Dynamo theory explains geomagnetism and why Earth’s field sometimes reverses its polarity.
Table of Contents