You've almost certainly seen the diagram – the layers of the Earth exposed as something more complex hard boiled eggs. The bark we live on is actually a thin shell with a hot (but still firm) cloak that forms a thick layer beneath it. In the center – against Jules Verne – there are inner and outer layers of core made up of iron. The outer core is the only layer that is liquid because the inner core is actually solid.
Although you will never visit the core, it will deeply affect your life. The Earth's magnetic field produces convection of the current outer core and directs the compass and protects us from the action of solar wind. The Earth's magnetic field history is a big question – not just because we are not really sure when the inner core hardens.
Magnets … well, you know
There are actually geological records of the magnetic field. Tiny crystals of magnetic minerals in the coolant magma will be aligned with the magnetic field before freezing in place. This can be useful because the Earth's magnetic field often turns the poles (which means that the pincers with the compass point to the geographical south). The orientation of these mineral needles also shows how close the equator was when they formed. The information that these minerals captured was the last piece that broke the tectonic plate case, and this allows us to understand where every continent was in the past.
We can also determine how many magnetic fields were from these records. This is what the team headed by Richard Bond and John Tardun at Rochester University were most interested in analyzing 565 million years old rocks in Quebec.
We do not have much data from that time period, which some researchers suspect might happen when the inner core finally began to be firm. In this case, the magma rocks that the researchers worked with slow cooling below the ground, which means their record probably covers about 75,000 years. This should be longer than usually the magnetic pole turns, so any such temporary changes should be average.
The team found that the magnetic field was incredibly weak in the observed time. The late jure period is highlighted by the fact that it has anomally weak magnetic field, but it was just about one fifth as strong as the time period. Moreover, it seems that the magnetic poles turned very often. It's a weird behavior.
This data actually fits with the limited information we have from the times that are closest to this point, which is also quite strange. And the study becomes really interesting when compared to the simulations of the Earth's core history. Some of these simulations have predicted that the core core was relatively recent in geological conditions, something that just happened at this time. In these models, the core reorganization causes the magnetic field to be wild for a while, shaking in a weakened state.
Researchers say their evidence fits into a scenario where the inner core began to consolidate roughly 565 million years ago – almost 4 billion years in Earth's life. This leads to questions about how the "geodynamic" that creates a magnetic field in the nucleus looked like this before and how it lasted so long. It also contributes to a fair list of strange things that happened in this chapter of Earth's history, which includes a remarkable evolutionary explosion of complex animal life.
In the summary that follows the work in Nature GeoscienceResearcher Carnegie Institution for Science Peter Driscoll (who was not involved in the study) provides the work needed to monitor this hypocritical hypothesis: "Additional paleomagnetic observations, both directions and intensity, are the next step to get a clearer picture of the core state around that time. skinning and iron conductivity will further limit the core thermodynamics. Finally, numerical models of developing cores can produce detailed predictions that test all these components together. "
And if this timeline of inner core formation is correct, Driscoll writes, "the nucleation of the inner core may have occurred just as it filled the geodesist and saved the Earth's magnetic shield."
Nature GeoscienceDOI: 10.1038 / s41561-018-0288-0, 10.1038 / s41561-019-0301-2 (O DOIs).