PRIMER : DEEP-SEA MINING

Why the next gold rush is happening at the bottom of the ocean

Down past the jellyfish, through the water column and beyond the light is the deep sea: the place between 200 to 11,000m (650 to 36,000ft) below the ocean's surface. The extremely high pressures and cold, dark conditions make unique habitats for the surprisingly colourful life here bizarre creatures like hairy-chested crabs and glittery Elvis worms.

But some people have their eyes on a different sort of riches formed in these unusual conditions: rare earth metals. Dr Helen Scales explains the drive to mine the materials buried in the deepest parts of the ocean.

THE WORD 'MINING' USUALLY BRINGS UP IMAGES OF GRUBBY FACES IN HARD HATS DISAPPEARING UNDERGROUND. SO WHAT IS MINING WHEN IT'S IN THE DEEP SEA?

It's just as grubby as mining on land - the difference is there aren't people actually in deep-sea mines. It's all going to be done remotely, using similar sorts of camera and robot technologies to those scientists are using to explore the deep sea. Only they'll be much bigger, with mining machinery bolted to them.

There are three main mining targets: polymetallic nodules, seamount crusts and hydrothermal vents.

For mining nodules - these dense lumps of rare metals - imagine a massive digger with caterpillar treads and, on the front, a massive scoop. That scoop is going to stick forks into the seabed and then drag them forwards, pick up the rocks and pop them into a tube a huge pipe that's several miles long and will suck those rocks up to the surface.