Is the supercontinent hiding underground? New research may challenge human understanding

Scientists have discovered two “supercontinents” buried deep in the Earth’s mantle, potentially reshaping human understanding of how the Earth’s interior operates.

According to a new study published in the journal “Nature,” these unknown regions within the Earth appear to be older and hotter than surrounding layers (including known subducting plates), with ages possibly reaching up to 500 million years.

This discovery suggests that the operation of the Earth’s mantle may differ from what we previously thought, with potentially lower fluidity and a mixing level far less than expected.

These buried “supercontinents” in the depths of the Earth are referred to by scientists as Large Low Shear Velocity Provinces (LLSVP), found respectively beneath Africa and the Pacific, approximately 1,200 miles (1,930 kilometers) below the surface.

Seismologists identified these structures by analyzing the speed and direction variations of seismic waves, similar to how ultrasound can reveal internal structures of the human body.

Arwen Deuss, a seismologist at Utrecht University in the Netherlands, stated, “No one knows if they are short-lived phenomena or have existed for hundreds of millions or even billions of years.” These islands are surrounded by structures descending to 3,000 kilometers deep through subduction.

Subduction is a geological process in which denser tectonic plates (such as oceanic plates) sink into the mantle, having previously shaped mountains and volcanoes on Earth. However, these “supercontinents” differ from subducting plates as they have higher temperatures.

“We know these ‘islands’ are located at the boundary between the Earth’s core and mantle, where seismic waves slow down because they are very hot,” explained Deuss. “But high temperatures alone do not fully explain these anomalies.”

Researchers found that the mineral grains in these structures are much larger compared to remnants of subducting plates. The higher number of smaller grains and boundaries in the subducting remnants increase the attenuation of seismic waves, whereas LLSVP almost has no attenuation, indicating their extremely ancient structure.

Similar to crystals or stalactites on the Earth’s surface, larger mineral grains represent a lengthier growth process, indicating that these “supercontinents” are older than surrounding subducting plates and may not have been involved in mantle convection.

This discovery suggests that the mantle may not flow as rapidly or mix as uniformly as imagined, preserving ancient stable structures and aiding geophysicists in gaining a deeper understanding of the formation and evolution of global volcanoes.