Technology Opens Promise, Perils Of Ocean Mining

Scientists have long known about remarkably pure concentrations of metals found near some of the hydrothermal vents, nicknamed "black smokers" because they resemble underwater chimneys.

The vents sprout in areas with heavy seismic activity, including the mid-Atlantic ocean ridge and the Pacific's volcanic "Ring of Fire," which stretches along the west coast of the Americas, to Asia and down near New Zealand. There, the earth's spreading plates allow sea water to seep into the earth's crust, where it becomes heated, leaching precious minerals from the surrounding rock.

Eventually, the water is hot enough to become buoyant and bursts toward the surface, similar to when cold milk is poured into a cup of coffee, gets heated and rises to the top. The minerals cool in the frigid sea water and solidify into the deposits.

About 200 active vents have been found, though only 10 nearby deposits are considered prolific enough to mine, according to a report by the International Seabed Authority. Dormant vents are much tougher to locate, but the deposits around them may also be fruitful.

The ISA report indicates a single deposit could weigh 100 million tons.