{"id":397627,"date":"2026-04-25T22:15:08","date_gmt":"2026-04-25T22:15:08","guid":{"rendered":"https:\/\/www.newsbeep.com\/nz\/397627\/"},"modified":"2026-04-25T22:15:08","modified_gmt":"2026-04-25T22:15:08","slug":"scientists-say-a-hidden-structure-may-exist-inside-earths-core","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/nz\/397627\/","title":{"rendered":"Scientists Say a Hidden Structure May Exist Inside Earth\u2019s Core"},"content":{"rendered":"

\"Inside<\/a>Scientists have found evidence that Earth\u2019s inner core may contain a previously unknown layer, suggesting the planet\u2019s center is more complex than once believed. Credit: Shutterstock<\/p>\n

Deep within Earth\u2019s core, scientists are uncovering signs of a hidden structure that challenges long-standing models of the planet\u2019s interior.<\/p>\n

Far below the surface, beyond the reach of drilling, Earth\u2019s core may contain a previously unknown layer.<\/p>\n

Scientists now believe Earth\u2019s center is not a single uniform sphere but a more complex structure, with a distinct zone buried inside the solid inner core. Often referred to as the \u201cinnermost inner core,\u201d this region is reshaping how researchers understand the planet\u2019s deepest interior and may hold clues to how Earth formed billions of years ago.<\/p>\n

Earth is traditionally divided into four layers: crust, mantle, outer core, and inner core. \u201cTraditionally we\u2019ve been taught the Earth has four main layers,\u201d said lead author Joanne Stephenson, a PhD researcher at The Australian National University (ANU). \u201cThe idea of another distinct layer was proposed a couple of decades ago, but the data has been very unclear.\u201d<\/p>\n

A study published in 2020 by researchers at The Australian National University (ANU)<\/a> in the Journal of Geophysical Research: Solid Earth identified signs of an additional layer within the inner core, pointing to a more complex structure at Earth\u2019s center.<\/p>\n

Probing the Inner Core With Seismic Waves<\/p>\n

The inner core is a dense, solid sphere made mostly of iron and nickel, with temperatures exceeding 5,000 degrees Celsius (9,000 degrees Fahrenheit). Although it accounts for only about 1 percent of Earth\u2019s volume, it provides important insights into the planet\u2019s history. Because it cannot be directly observed, scientists study it using seismic waves from earthquakes. These waves travel at different speeds depending on the materials they pass through.<\/p>\n

\"Seismic<\/a>(a) Example seismogram showing the arrivals of PKPdf (PKIKP), PKPbc, and PKPab for an epicentral distance of 152\u00b0 for an event from the South Sandwich Islands recorded in Alaska. (b) Theoretical travel time curves for the three IC phases in terms of epicentral distance. (c) Ray paths of PKPdf, PKPbc, and PKPab (labeled) through the Earth for an epicentral distance of 152\u00b0. \u03be denotes the angle between the tangent to the PKPdf ray and the Earth\u2019s rotational axis. The inner core boundary is denoted by ICB. IC, inner core; ICB, IC boundary. Credit: Stephenson et al., Journal of Geophysical Research: Solid Earth, 2020<\/p>\n

The ANU team analyzed decades of seismic data using an advanced algorithm that tested thousands of models. Instead of averaging the data, which can hide subtle features, they examined the wave patterns more closely. This approach revealed a shift in seismic behavior about 650 kilometers (roughly 400 miles) from Earth\u2019s center, suggesting a boundary within the inner core.<\/p>\n

Evidence for a Distinct Central Region<\/p>\n

One important clue comes from anisotropy, meaning seismic waves move at different speeds depending on their direction. In many models, waves travel faster along Earth\u2019s rotational axis than along the equator. In this newly identified central region, that pattern shifts.<\/p>\n

The slowest wave speeds occur at an angle of about 54 degrees relative to the rotation axis, indicating a different alignment of iron crystals.<\/p>\n

Lead author Joanne Stephenson explained that this difference may reflect major events in Earth\u2019s past. \u201cWe found evidence that may indicate a change in the structure of iron, which suggests perhaps two separate cooling events in Earth\u2019s history,\u201d Stephenson said. She added that this hidden layer could reflect \u201can unknown, dramatic event in the Earth\u2019s history,\u201d though its exact nature remains uncertain.<\/p>\n

Independent Confirmation From New Techniques<\/p>\n

Further support came in 2023 from a study in Nature Communications that used a different seismic technique. Instead of focusing only on direct earthquake waves, researchers analyzed rare signals that bounce through Earth multiple times<\/a>. Some of these waves pass through the core up to five times, providing more detailed information.<\/p>\n

These repeated signals revealed a similar central region about 650 kilometers (roughly 400 miles) across. In this area, seismic waves again showed directional differences, with the slowest speeds occurring at about 50 degrees relative to Earth\u2019s rotation axis. The surrounding part of the inner core appeared more uniform, with weaker directional variation.<\/p>\n

These results could help resolve why some past experiments have not matched existing models of Earth\u2019s interior.<\/p>\n

Scientists have long suspected the presence of a deeper layer within the inner core, with earlier clues suggesting that the iron crystals there may be arranged in different ways.<\/p>\n

Implications and Remaining Uncertainties<\/p>\n

These findings could help resolve why some past experiments have not matched existing models of Earth\u2019s interior. However, researchers acknowledge that there is still work to be done. \u201cWe are limited by the distribution of global earthquakes and receivers, especially at polar antipodes,\u201d the ANU team wrote, noting that gaps in data can reduce confidence in some models.<\/p>\n

Future studies may close these data gaps, giving researchers a clearer picture of the events recorded deep within Earth\u2019s earliest history. But even with current data, the implications are massive.<\/p>\n

\u201cIt\u2019s very exciting\u2014and might mean we have to re-write the textbooks!\u201d Stephenson remarked.<\/p>\n

References:<\/p>\n

\u201cEvidence for the Innermost Inner Core: Robust Parameter Search for Radially Varying Anisotropy Using the Neighborhood Algorithm\u201d by J. Stephenson, H Tkal\u010di\u0107 and M. Sambridge, 7 December 2020, Journal of Geophysical Research: Solid Earth.
DOI: 10.1029\/2020JB020545<\/a><\/p>\n

\u201cUp-to-fivefold reverberating waves through the Earth\u2019s center and distinctly anisotropic innermost inner core\u201d by Thanh-Son Ph\u1ea1m, and Hrvoje Tkal\u010di\u0107, 21 February 2023, Nature Communications.
DOI: 10.1038\/s41467-023-36074-2<\/a><\/p>\n

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