The massive seafloor hydrothermal vent field in the dark depths of the eastern Pacific Ocean is the hottest and largest discovered in the region.
Moreover, it is located in a place where scientists did not expect to find active vents, not to mention their whole system, hundreds of meters from the axis of the volcanic ridge.
The discovery could have a significant impact on our understanding of vent systems and the role they play in ocean ecosystems, the scientists say.
The field was discovered by a team of scientists using autonomous underwater vehicles to map the seafloor at depths unfavorable for human explorers.
Based on data from the Woods Hole Oceanographic Institution AUV. Hourlythe team saw an area of huge spiers up to three stories high, 2,560 (8,400 feet) meters below the surface—in silent, permanently dark bathypelagic depths.
Initially, the team thought the vents were extinct, but upon closer inspection, it turned out otherwise.
“We were amazed that this field is not only very active, but also larger and warmer than any other hydrothermal vent field known along this part of the East Pacific Rise that has been studied over the past 30 years.” says marine geologist Daniel Fornari of WHOI.
Hydrothermal vents are home to some of the most amazing ecosystems on earth. These are openings in the seafloor through which heat and chemicals escape from our planet’s crust, usually associated with volcanic activity.
The vent plumes themselves can be scalding hot, over 400 degrees Celsius (750 Fahrenheit), but life thrives in their immediate vicinity.
Most life on Earth depends on the photosynthetic food web, but below, in the bathypelagic darkness, life takes a different path. Chemicals deposited by vents feed the chemosynthesis-based food web, using chemical reactions to generate energy rather than sunlight.
Not only is this amazing evidence that “life finds a way out,” but it also reveals the mechanism by which life can exist on other worlds, such as the solar system’s icy moons Enceladus and Europa.
They are also very important to the ocean as a whole, providing a transportation system from the Earth’s interior that helps regulate ocean chemistry and temperature. But since they are often found at depths that are not particularly hospitable to humans, our understanding of them is indeed incomplete.
Usually, searches for hydrothermal vent systems in the eastern Pacific Ocean are concentrated near the axes of the ridges and centers of volcanic activity.
Here, a team led by ocean chemist Jill McDermott of Lehigh University sought to better map the area west and east of the East Pacific Rise axial trough using Hourlysonar to create 3D seabed maps.
“The mapping work provides a detailed picture of the seafloor so that we can track and quantify the changes that occur when the next volcanic eruption occurs along this part of the East Pacific Rise ridge axis,” explains McDermott.
It was during this survey that the team saw the peaks of a huge vent field 750 meters east of the ridge axis and 5 to 7 km north of the closest known active vents on the axis.
Samples from nine vents showed a temperature of 368 degrees Celsius, and elements whose presence suggested a temperature of origin were even higher – a minimum of 437 degrees Celsius for the observed ratio of iron to manganese.
Overall, the field covered an area equivalent to a football field, the team said. Its proximity to a fault line suggests that it is controlled by tectonic activity.
Scientists believe the vents could help restore nearby hydrothermal ecosystems after volcanic eruptions. There have been two eruptions on the East Pacific Rise in recent decades; one from 1991 to 1992 and the other from 2005 to 2006. Another one is expected in a few years, the researchers said.
Wider exploration of the deep seafloor could reveal new vent fields in unexpected places, which in turn will help us better understand how these near-alien ecosystems work.
“Much remains to be learned about deep-sea vents along the global mid-ocean ridge, both in terms of their location and in terms of their geological, geochemical and biological characteristics,” says McDermott.
“I hope our study will motivate future research efforts to target off-axis mapping along the global mid-ocean ridge ridge to better define the extent of off-axis versus axial hydrothermal release.”
The study was published in PNAS (link not yet active at the time of writing).
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