A 620-mile-long "plume of iron and other nutrients" billowing out of hydrothermal vents calls into question researchers past beliefs about iron distribution.

"This study and other studies like it are going to force the scientific community to reevaluate how much iron is really being contributed by hydrothermal vents and to increase those estimates, and that has implications for not only iron geochemistry but a number of other disciplines as well," Mak Saito, a WHOI associate scientist and lead author of the study, said, according to a Woods Hole Oceanographic press release, reported.

Researchers set out across the South Atlantic Ocean to map out the microbial life and chemical composition of the water. They weren't expecting to find the iron plumes.

The team's route passed over an area where some of the Earth's major tectonic plates are starting to separate. There are faster-spreading ridges in other parts of the world that are more active, so this area had never been a priority for study.

Past studies used helium to detect vent activity in the area and found very little, scientists were not expecting to see iron flowing freely from the vents.

The team studied samples they had taken during the experiment, and found high levels of magnesium and iron that formed a distinctive "plume." The area had 80 times more iron than is seen in faster-spreading plates.

"We had never seen anything like it," Saito said. "We were sort of shocked-there's this huge bull's-eye right in the middle of the South Atlantic Ocean. We didn't quite know what to do with it, because it went contrary to a lot of our expectations."

The finding contradicts the belief that slow-spreading ridges emits little iron and nutrients, and also calls into question the accuracy of helium testing.

"We've assumed that low helium means low iron, and our study finds that that's not true," Saito said. "There's actually quite a lot of iron coming out of these slow-spreading regions in the Atlantic, where people thought there would be little to none."

Much of the ocean's floor is made up of slow-spreading ridges, and these findings suggest iron might be more abundant in similar areas than researchers previously believed.