One of the reasons I could never be a serious scientist is because when I read stories about “mysterious signals” from “huge objects” inside the Earth, my mind goes to every creepy science fiction novel I’ve ever read.

But if it’s not some kind of creature set on destroying the human race, then what is sending the signals?

The objects are “super-continent-sized” and are buried in the Earth’s mantle, and according to recent audio scans of their composition, are also very old.

Arwen Deuss, a seismologist from the Netherlands and co-author of this paper, explains that the Earth expands and contracts during seismic events and we can learn a lot by “listening.” The quality of the tones it produces revealed these two “low-shear velocity provinces (LLSVPs), or superplumes” far underground.

What researchers haven’t been able to figure out, though, is why the objects don’t make the sound waves any less powerful.

At least, until now.

“Nobody knew what they are, and whether they are only a temporary phenomenon, or if they have been sitting there for millions or perhaps even billions of years. These two large islands are surrounded by a graveyard of tectonic plates which have been transported there by a process called subduction, where one tectonic plate dives below another plate and sinks all the way from the Earth’s surface down to a depth of almost three thousand kilometers.”

The researchers theory is that grain size, instead of temperature alone, is compromising the LLSVP. They posit the structures are made up of larger (but fewer) grains, which results in fewer boundaries between them. Every time an LLSVP crosses one of the boundaries it loses energy, and the sound is dampened.

It would take a very long time for grains to grow to larger sizes, which means the LLSVPs are older than the surrounding subducted slabs.

They could be as old as the entire planet, though without a way to measure them more accurately, we may never know for sure.

If you thought that was interesting, you might like to read about the mysterious “pyramids” discovered in Antarctica. What are they?