The oceans cover about 70% of Earth’s surface. Scientists have estimated that nearly fifty percent of the earth’s living species reside in the oceans, and 97% of the water on Earth is contained within them.

Most people learn these facts in science class at a young age. But one thing most people probably don’t associate with the ocean is mining.

Sure, we drill for oil and in relatively shallow offshore waters. But when it comes to mining – gathering ore rich rocks, processing them, and selling the end product for a profit – we haven’t even scratched the surface of the seafloor’s mineral wealth.

There are good reasons why seafloor mining hasn’t historically been successful. For one thing, conditions in the deep ocean are extreme, requiring the development of robotic technology capable of collecting and processing deposits automatically.

But there’s a much bigger reason seafloor mining hasn’t taken off. It simply isn’t profitable.

Building and maintaining an army of mining robots is an expensive proposition. The prices of metals simply haven’t been high enough to support extraction.

However, some people see this changing in the near future. Concerns about upcoming shortages of rare earth elements – critical to modern electronics – have led some to predict that seafloor mining may soon become commonplace. The prices of other metals have also been rising as demand continues to grow and production growth from existing mines slows.

Some companies have already been experimenting with seafloor mining, although none has yet extracted metals in particular at a profit.

How do metal deposits end up on the seafloor? And how do companies know where to look for them?

It turns out that finding minerals on the seafloor is actually pretty straightforward. Most operations would probably focus on massive sulphide deposits. These large, concentrated deposits form as hot, mineral laden water emerging from the seafloor at hydrothermal vents is cooled by seawater near the freezing point, causing minerals to precipitate out of solution. The precipitated minerals, which are sometimes reworked by microorganisms, can form structures on the seafloor.

To find the structures, companies would just need to travel to a mid-ocean ridge. The slower the seafloor around the ridge is spreading, the larger the deposits will be. That’s because faults that allow for fluid flow from depth tend to be longer and more continuous in these regions.

Although undersea mining shows promise, some scientists are worried about the environmental consequences. On land, where we understand how ecosystems function, we can manage environmental impacts. At a poorly understood mid ocean ridge thousands of feet beneath the surface of the sea, managing environmental impacts would be difficult at best.

For more in depth coverage of undersea mining, take a look at these articles: