Jules Verne’s renowned novel “Journey to the Center of the Earth” portrays explorers descending through an Icelandic volcano to a massive underground realm inhabited by ancient creatures, but the reality of the Earth’s core is quite different from this imaginative portrayal, and in certain aspects, even more awe-inspiring.
Scientists announced on Tuesday that an extensive investigation of the Earth’s deep interior, utilizing seismic waves produced by significant earthquakes, has verified the existence of a unique configuration at the center of our planet. This structure is a solid sphere composed of iron and nickel, extremely hot and approximately 1,350 km in diameter.
The Earth has a diameter of roughly 12,750 km and is composed of four layers: an outer rocky crust, a rocky mantle, a liquid outer core, and a solid inner core. In the 1930s, the existence of the solid inner core, which is around 2,440 km in width, was discovered using seismic waves that traveled through the planet.
In 2002, scientists proposed the notion that a distinct innermost layer, akin to a Russian Matryoshka nesting doll, was hidden within the inner core. Recent advances in seismic monitoring technology have allowed this theory to be verified.
Seismic waves generated by earthquakes travel through the Earth and provide valuable insight into the planet’s internal structure by measuring the shape of the waves. Previously, scientists could only detect these waves reflecting up to two times, from one side of the planet to the other and back. However, a recent study has analyzed the waves produced by over 200 earthquakes with magnitudes exceeding 6.0, bouncing as many as five times within the planet, much like ping pong balls.
Thanh-Son Pham, an observational seismologist at the Australian National University in Canberra and the lead author of the study published in the journal Nature Communications, remarked that our awareness regarding the Earth’s deep interior may be inferior to our understanding of the surface of remote celestial bodies. He stated, “We may know more about the surface of other distant celestial bodies than the deep interior of our planet.”
“We analyzed digital records of ground motion, known as seismograms, from large earthquakes in the last decade. Our study becomes possible thanks to the unprecedented expansion of the global seismic networks, particularly the dense networks in the contiguous U.S., the Alaskan peninsula and over the European Alps,”
Pham said.
The outer layer of the inner core, along with the newly verified innermost sphere, are composed of a solid iron-nickel mixture that can reach molten temperatures, yet remain in a solid state due to the immense pressure present at the Earth’s core.
“I like to think about the inner core as a planet within the planet. Indeed, it is a solid ball, approximately the size of Pluto and a bit smaller than the moon,”
“If we were somehow able to dismantle the Earth by removing its mantle and the liquid outer core, the inner core would appear shining like a star. Its temperature is estimated to be about 5,500-6,000 degrees (Celsius/9,930-10,830 Fahrenheit), similar to the sun’s surface temperature,”
said Australian National University geophysicist and study co-author Hrvoje Tkalčić
According to Pham, the boundary between the outer section of the inner core and the innermost sphere seems to be a gradual transition rather than an abrupt one. The scientists were able to distinguish between these two areas based on the distinct behavior of the seismic waves that passed through them.
Over time, the Earth’s inner core is expanding by converting liquefied substances into solids, depleting the outer core in the process, as the planet cools down continuously since its formation approximately 4.5 billion years ago.
“The latent heat released from solidifying the Earth’s inner core drives the convection in the liquid outer core, generating Earth’s geomagnetic field,”
“Life on Earth is protected from harmful cosmic rays and would not be possible without such a magnetic field.”
In addition, Pham said.
