Scientists discovered six mysterious regions deep inside Earth — and have no idea what they are

Scientists from the Chinese Academy of Sciences trained artificial intelligence to analyze over 2 million seismic records from 5,000 earthquakes between 1990 and 2024. The system identified six unknown regions at the boundary between the mantle and outer core, at a depth of about 2,900 km. Researchers speculate they may be remnants of tectonic plates that sank or possibly remnants from the planet Theia, but have not yet determined their nature with certainty.

Scientists from the Chinese Academy of Sciences used artificial intelligence to analyze more than two million seismic records collected from nearly 5,000 earthquakes between 1990 and 2024. The system, trained to detect particularly weak signals, produced a database of nearly 175,000 high-quality signals — more than ten times all previous studies combined. The analysis revealed six unknown regions at the boundary between the mantle and outer core, at a depth of about 2,900 km, where significant differences were found that had not been documented before. Researchers estimate that these regions may contain material different from the surrounding rocks — possibly remnants of tectonic plates that sank to great depths over millions of years, or alternatively remnants of the ancient planet Theia, which collided with Earth about 4.5 billion years ago and led to the formation of the Moon. However, the current study does not prove a connection to Theia. The discovery may help in the future to understand the movement of heat and material within the Earth, processes that affect volcanic activity and tectonic plate movement. For now, the six regions are targets for further research.