Researchers from Utrecht University have found in a study that there are two colossal peaks that reach heights of around 620 miles (1,000), in what have been described as 'islands'. They can be found about 1,200 miles (2,000km) below the Earth's crust, and are said to be at least half a billion years old.

The LLSVPs are found in what scientists refer to as "slab graveyards," where tectonic plates sink through a process called subduction.

Deep within Earth’s mantle lie two enormous regions, often referred to as "islands," which are the size of continents.

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.