Q: What exactly is deep-sea mining?

It is the process of retrieving mineral deposits from the deep sea - the area of the ocean below
200m.

Around 90% of the ocean - and 50% of the Earth's surface - is considered the deep sea. Since 1982, around 1.4 million sq km have been explored, mostly in the Pacific Ocean. But this only amounts to 0.0001% of the area open to explore. Now, more companies are looking to expand into the deep sea to search for deposits.

Q: Why are companies so keen to mine the deep sea?

Companies have their eye on minerals deposited in three different parts of the ocean. Most exciting - and most popular - are polymetallic nodules. These are bundles of ore that look like potatoes. They litter the ground on abyssal plainsA flat area of the ocean floor, usually around 3,000m deep. They cover more than 50% of the Earth's surface. - flat areas of the seafloor. The nodules are rich in manganese, nickel, cobalt and rare earthsA set of 17 metallic elements found in the Earth's crust.. Up to 10cm in diameter, they grow at a rate of just a few centimetres every one million years.

Elsewhere, sulfide deposits rich with gold, silver, lead and zinc have been found on ridges near hydrothermal vents. And underwater mountains have rich cobalt crusts.

As the price of rare earths and certain metals go up, it is becoming clear that companies and countries could make billions of dollars by setting up deep-sea mines.

Q: What are all the minerals used for?

Many of the minerals available underwater are used to make batteries as well as in renewable energy manufacturing. Supporters of deep-sea mining argue that we need these metals and minerals to help with the green revolution.

The lithium to be found under the sea could be used to create millions of electric vehicles, wind turbines or solar panels - as well as mobile phones.

Q: Can't we get these on dry land?

We can - but current land mining is known to cause severe environmental problems including air and water pollution, soil erosion and loss of biodiversityBiodiversity is all the different kinds of life you'll find in one area - the variety of animals, plants, fungi, and even microorganisms like bacteria that make up our natural world. Each of these species and organisms work together in ecosystems, like an intricate web, to maintain balance and support life. . And the mining of some elements, such as cobalt, is centred in countries where children are known to carry out dangerous work.

Plus, resources are running out. It's calculated that by 2050, demand for cobalt and nickel will be four times greater than the available reserves on land. The answer, many mining companies argue, is in the oceans.

Q: So what is the problem?

Some are concerned that the environmental impacts of underwater mining could be even worse than those on land. Duncan Currie, an international lawyer says: "You are talking about the destruction of the habitat. Any area you are mining will be destroyed."

And given the size and mystery of the ocean floor, many experts worry that the implications are completely unpredictable. The sediment and water returned to the ocean after the mining process will create almost constant plumes. "No one has any idea what it will do", Currie warns, "It's incredibly important and we know almost nothing."

Q: What is next for the deep sea?

It is down to regulation. International waters, known as the high seas, are controlled by the International Seabed AuthorityA United Nations body charged with regulating human activities on the deep sea floor. It has issued 30 contracts for mineral exploration since 1982. (ISA). Last month, the Pacific Island of Nauru, located in the Clarion-Clipperton ZoneAn area in the Eastern Central Pacific Ocean estimated to contain three to six times more cobalt reserves than all known land reserves combined., triggered a clause in the law that gave the ISA two years to finalise rules. If they are not ready by then, companies will be able to start mining at will.

But at the same time, more than 350 scientists from 44 countries signed a petition calling for a moratorium on deep-sea mining "until sufficient and robust scientific information has been obtained".