The most surprising truths are usually the ones we don't expect to find, like those 5.100 kilometers below the surface. According to a new study that changes what we know about the Earth's center, the planet's inner core is not a solid, rigid mass, but a dynamic structure that can be deformed.
The discovery that changes everything
Complete solidity at the center of the Earth has been the model for decades, if not forever. That notion is now under scrutiny by new research that reveals that the inner core can, in fact, deform. The discovery, published in the journal Nature, not only settles a long-standing debate about what was happening at the core of the planet, but it also raises new questions about how these changes might alter the length of our 24-hour day and Earth's magnetic field. "After decades of research and debate, we are now getting closer to a clearer picture of how the inner core is changing," says Xiaodong Song, a seismologist at Peking University, who was not involved in the study.
An innovative method of study
The researchers made this discovery by analyzing how seismic waves from earthquakes traveled from the South Sandwich Islands in the South Atlantic Ocean to seismometers in Alaska and Canada, on the other side of the planet. The waveforms of some seismic signals changed between 2004 and 2008, and these changes occurred because the waves briefly penetrated the Earth's inner core, which was changing shape.
“For the first time we are seeing that it is deforming,” he says. John Vidale, seismologist ofUniversity of Southern California in Los Angeles, who together with his colleagues published the discovery on Nature Geoscience (I link it to you here).
The center of the Earth is “dynamic”
Earth's inner core is surrounded by an outer core, and the interface between the two, about 5.100 kilometers below the planet's surface, is a rather mysterious realm. Previous seismic studies have revealed that the inner core is made of solid metal and rotates inside a superfluid, hot outer core composed mostly of metals like iron and nickel.
The researchers then monitored how this rotation speeds up and slows down over time, and found that it occurs at a slightly different rate than the rest of Earth.
New perspectives and theories
Some scientists have argued that changes in seismic signals traveling through the Earth are not due to rotational changes in the core, but to physical changes at the boundary between the inner and outer core. However, this new study implies that both explanations are valid: Many of the changes in the waveforms of the South Sandwich Islands earthquakes can be traced back to the rotation of the core, while other changes were probably triggered by the stretching of the boundary separating the inner and outer cores.
Earth's Center Changes Shape: The Implications for Our Planet
The study sheds light on a fluid, moving inner Earth: essentially, as crystals in the outer core form, the inner core slowly grows. This process induces movement in the outer core and maintains Earth’s magnetic field. Variations in how the inner core rotates may be another factor that affects the length of our day.
“Ideally, we would like to connect all these things we are seeing to make the deep center of the Earth less mysterious,” he says. vidale. Studies are ongoing that continue to reveal new features of how the internal mechanisms of our planet work, showing how dynamic and complex the system that hosts us is.
These deep mechanisms aren’t just interesting in themselves; understanding them can help us predict changes in Earth’s magnetic field and other phenomena that can directly affect life on the planet’s surface. Such a discovery opens up new avenues for investigation and serves as a reminder of how little we really know about our extraordinary world.
