Earth’s core is growing out of balance, scientists have found, but it’s not clear why.
The dense iron core in the center of the planet has grown faster beneath Indonesia’s Banda Sea, according to findings by seismologists at the University of California at Berkeley.
The growth on one side of the molten metal is a product of iron crystals that form when molten iron cools, but something in the Earth’s core or outer mantle beneath the Southeast Asian nation is giving off heat at a faster rate than on the other hand. side, under Brazil. The faster the cooling, the faster the iron crystallization occurs – and the faster its growth accelerates.
Such differences have important implications for Earth’s magnetic field, and it is the convection currents in the core that generate these fields that protect us from harmful solar particles.
While the core is solid iron, it is surrounded by a molten outer core and then a mantle of hot rock. In the mantle and outer core, heat from crystallized iron and warmer rock in the mantle rises to the surface, pushing cooler material down. This movement produces a magnetic field.
“We provide a rather loose limit on the age of the inner core – between half a billion and 1.5 billion years – which may be useful in the debate about how magnetic fields were generated before they existed. strong inner core,” said Barbara Romanowicz, professor at UC Berkeley in the Graduate School of the Department of Earth and Planetary Sciences and director emeritus of Berkeley Seismology Laboratory (BSL).
“We know that magnetic fields existed three billion years ago, so other processes must have caused convection in the outer core at that time.”
The relatively young age of the inner core suggests that, in the history of our planet, the heat holding molten iron came from the lighter elements separated from the iron, and not from the crystallization of iron. But tricky questions remain: “If the inner core can only exist for 1.5 billion years… then where did the old magnetic field come from?” BSL deputy scientist Daniel Frost poses. “That’s where the idea of this dissolved light element came from, which then solidified.”
One possible explanation is plate tectonics, with cold plates cooling the mantle as they sink into subduction zones, but it’s not clear if the cooling of the mantle could have an impact on the inner core.
However, the asymmetrical growth of the nucleus answers a mystery that scientists have been trying to solve for 30 years: why does the crystallized iron core appear aligned along the Earth’s axis of rotation further west than ‘to the East? Seismic waves travel faster in a north-south direction than along the equator, due to the asymmetry of the iron crystals, and this difference in growth is one possible explanation.
“The simpler model looks a bit unusual — that the inner core is asymmetrical,” Frost said. “The west side is different from the east side all the way to the center, not only at the top of the inner core, as some say. The only way to explain this is that one side grows faster than the other. “
As the iron crystals grow, gravity redistributes the overgrowth from east to west in the inner core. Movements in the soft solids of this inner core line up along the crystal lattice, showing the scientists’ computer model. In the east, the core grows 60% more than in the west, which explains the difference in the speed of seismic waves that can cause earthquakes, volcanic eruptions and other phenomena.
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