It is easy to forget, as we go on with our lives, that we stand on a flimsy layer of rock above the intricate and complex layers of the Earth’s interior. And while it is mildly terrifying, the good news is that we are getting better at understanding what goes on below our feet. Some of the latest info actually has historical roots.
In an extremely detailed review article on The Conversation, Dr Christopher Davies from the University of Leeds discusses the mysterious “geomagnetic spike” that happened in the Middle East around 1000 BCE. The evidence for the spike comes from copper slag produced during smelting.
The copper from the original research was found in Jordan and Israel, and researchers expanded the search to other Iron Age sites. Similar magnetic signatures were seen in Turkey, Georgia, and China but not in samples from Cyprus, Egypt, and India. This allowed the researchers to estimate that the spike couldn’t have been much wider than 2,000 kilometers (1,240 miles).
This event was one of the most extreme variations in the Earth’s magnetic field ever recorded. The cause is not exactly clear. Something happened in the Earth’s core. The magnetic field is produced by the liquid core. It is heated by radioactive elements at the very center of our planet and passes the heat to the above rocky layers. This heat gradient leads to turbulent motions and the spike might have been caused by a jet of molten iron shooting up.
While this appears to be a pretty good solution, it has drawbacks and leads to several more questions. To create such a localized spike, the material in the core must be moving five to 10 times faster than it has been in the last 200 years. It also suggests that there are localized flows rather than the modeled global one.
Davies discusses the risk associated with changes in the magnetic field. There is no evidence that such changes are harmful to life but they might become problematic when solar storms reach weak spots, as they could damage our electronics. There's currently an area of weaker magnetic field over the South Atlantic.
There’s so much we still don’t know about the core, but new numerical simulations might help with that.
[H/T: The Conversation]