Deep inside the Earth lie massive mountain ranges with peaks four times higher than Everest. No one knows why.

It was a sunny summer day in Antarctica. Samantha Hansen watched the colourless landscape through her frozen eyelashes – a white wall where the land seamlessly merged with the sky. In these disorienting conditions, with the air temperature at approximately -62 °C (-80 F), she found a suitable spot in the snow and thrust her shovel into it.

S. Hansen was in the gloomy interior of the continent – not the relatively picturesque Antarctica known from cruise ship excursions, but a brutal environment where even local animals rarely dare to venture. As part of a team of researchers from the University of Alabama and Arizona State University, Samantha was searching for hidden mountain ranges – peaks upon which no explorer has ever set foot and which have never been illuminated by sunlight. These mountains are located deep within the Earth.

In 2015, researchers arrived in Antarctica to install a seismological station – equipment half-buried in the snow that would allow them to study our planet's interior. The team installed 15 such stations in Antarctica.

The mountain-like structures inside the Earth are very mysterious. Samantha Hansen's team discovered that these ultra-low velocity zones or ULVZs (ultra-low velocity zones), as they are called, are likely to be found almost everywhere – wherever you are in the world, they could be hiding deep, deep beneath your feet.

“We found evidence of ULVZs everywhere we looked,” says S. Hansen. The question is – what are they? And what do they “do” deep inside our planet, and why?

A mysterious history

The Earth's strange internal mountains form between the planet's metallic core and the rocky mantle surrounding it. This sharp transition, as pointed out by S. Hansen's research team, is even more extreme than the change in physical properties between a solid rock massif and air. It has baffled experts for decades – it is equally enigmatic and influential on the planet's geology.

Although the “core-mantle boundary” is located thousands of kilometres below the Earth's surface, there is a surprisingly high level of interaction between its vast depths and our world. It is believed to be a kind of graveyard for ancient pieces of ocean floor, and it may be the basis for the existence of volcanoes in unexpected places, such as the Hawaiian Islands, because it creates a heated path to the Earth's crust.
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