Earth's biggest mountains, more than 100 times taller than Mount Everest, have been discovered on the boundary between Africa and the Pacific Ocean, a groundbreaking research, published in the journal Nature, has confirmed. The two peaks lie deep beneath the Earth's surface and reach heights of around 1,000 km, far bigger than the 8.8 km height of Mount Everest. Researchers estimate that the mountains are at least half a billion years old but could date back to the formation of Earth four billion years ago.
"Nobody knows 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," said head researcher Dr Arwen Deuss, a seismologist and professor of Structure and composition of Earth's deep interior at Utrecht University, as per The New York Post.
According to the research, two monstrous structures sit on the boundary between Earth's core and the mantle, the semi-solid area beneath the crust, beneath Africa and the Pacific Ocean. They are surrounded by a massive "graveyard of tectonic 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 kilometres," said Dr Deuss.
Scientists have known for decades that there are massive structures hidden deep within the Earth's mantle thanks to seismic shockwaves rippling through the Earth's interior. Large earthquakes cause the planet to ring like a bell, and it will sound "out of tune" when it hits anomalous objects such as the supercontinents. So, by listening carefully to the tone that arrives on the other side of the planet, scientists are able to build up a picture of what lies beneath.
"We see that seismic waves slow down there," said Dr Deuss while discussing how they happened to discover the underground mountains, which are referred to as "Large Low Seismic Velocity Provinces" or LLSVPs for this reason.
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According to the research, the new structures are hotter than their neighbouring tectonic plates. Scientists were thrown for a loop when studying the so-called damping of seismic waves, which is the "amount of energy that waves lose when they travel through the Earth," explained Dr Duess' colleague Sujania Talavera-Soza.
"Against our expectations, we found little damping in the LLSVPs, which made the tones sound very loud there," she said, adding, "But we did find a lot of damping in the cold slab graveyard, where the tones sounded very soft."
This was unlike the upper mantle, which was expectedly "hot" with damped waves, researchers said. Ms Sujania analogized the phenomenon to going for a run in hot weather, explaining, "you don't only slow down, but you also get more tired than when it is cold outside."
Ultimately, the study suggests that the mountains are made up of much larger grains than the surrounding slabs since these wouldn't absorb so much energy from passing seismic waves.
"Those mineral grains do not grow overnight, which can only mean one thing: LLSVPs are lots and lots older than the surrounding slab graveyards," said Ms Sujania.
