Two hidden mountains, more than 100 times larger than Mount Everest have been discovered deep underground. The two ‘islands of rock’ each measure more than 620 miles / 998km tall, dwarfing anything found on Earth’s surface and making Mount Everest look like an anthill. Scientists at the University of Utrecht uncovered the sizable duo around 1,200 miles / 1931km beneath Africa and the Pacific Ocean, on the boundary between Earth’s core and mantle layers.

The two are estimated to be at least half a billion years old but could date back as far as four billion years to Earth’s creation. “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,” Head Researcher Dr Arwen Deuss told the . The existence of the two mountains was confirmed by scientists using seismic measuring technology.

like an earthquake sends shock waves rippling through the earth. When these waves pass through dense, or hot objects, they’re slowed and weakened. By listening to the tone of seismic activity, scientists can map out structures thousands of miles beneath our feet.

Seismic waves passing through the two giant structures slowed drastically, revealing the mountains’ whereabouts. At 29,032ft / 8,849m tall, Mount Everest is the tallest mountain on Earth, measured from sea level. Around the Nepaleese behemoth each year, with roughly five to ten people losing their lives.

Last year, on Moun.