Some of the Earth’s most “extreme features” have been discovered deep, deep underground, and scientists can’t work out what they are.The mysterious zones have the power to slow down seismic waves by up to 50 per cent, yet experts don’t know what they’re made of or what role they play.These strange b...

The mysterious zones have the power to slow down seismic waves by up to 50 per cent, yet experts don’t know what they’re made of or what role they play.

These strange black holes (figuratively speaking) are located within the Earth’s lower mantle – near the core – and are known as ultra-low velocity zones (ULVZs).