Monster Hydrothermal Field Found in the Dark Depths of the Eastern Pacific

The large field of hydrothermal vents on the seafloor in the dark depths of the East Pacific ocean is the hottest and largest ever found in the region.

Not only that, but in places where scientists don’t expect to find active vents, let alone the entire system, hundreds of meters from the axis of the volcanic ridge.

The discovery, scientists say, could have a significant impact on our understanding of ventilation systems, and the role they play in marine ecosystems.

The field was discovered by a team of scientists using autonomous underwater vehicles to map the ocean floor at depths inhospitable to human explorers.

In the data obtained from the AUV. Woods Hole Oceanographic Institution Securitythe team looked at the region of the massive tower, standing three stories high at 2,560 (8,400 feet) meters below the surface – in permanently dark and silent bathypelagic depths.

Ventilation is monitored with a temperature recorder. (WHOI/NDSF/ROV Jason/NSF)

Initially, the team thought the vents were extinct, but a closer look revealed otherwise.

“We were surprised that not only is this field highly active, but also that it is wider and its origin temperature hotter than any other known hydrothermal vent field along this part of East Pacific Rise that has been studied over the last 30 years,” said marine geologist Daniel Fornari. from WHOI.

Hydrothermal vents are home to some of the most interesting ecosystems on Earth. They are openings in the ocean floor through which heat and chemicals are ejected from our planet’s crust, usually associated with volcanic activity.

The vent clumps themselves can be very hot, over 400 degrees Celsius (750 Fahrenheit), but life thrives near them.

Most life on Earth depends on a photosynthetic food web, but under bathypelagic darkness, life takes a different route. Chemicals stored by ventilation feed a food web based on chemosynthesis, harnessing chemical reactions for energy rather than sunlight.

Not only is this extraordinary evidence for “life finding a way”, but it also reveals the mechanisms by which life might exist on other worlds, such as the icy Solar System moons Enceladus and Europa.

They are also very important to the ocean as a whole, supplying transportation systems from the Earth’s interior that help regulate ocean chemistry and temperature. But, because they are often found at depths that are not very hospitable to humans, our understanding of them is truly incomplete.

Typically, the search for hydrothermal vent systems in the Eastern Pacific is concentrated near the axis of the ridge, and the locus of volcanic activity.

Here, a team led by chemical oceanographer Jill McDermott of Lehigh University is attempting to better map the western and eastern regions of the East Pacific Rise axial trough, using Securitysonar to produce a three-dimensional map of the ocean floor.

A spectacular chimney on site. (WHOI/NDSF/ROV Jason/NSF)

“The mapping work provides a detailed picture of the seafloor so that we can monitor and measure changes that occur when the next volcanic eruption occurs along this part of the axis of the East Pacific Rise ridge,” explains McDermott.

It was during this survey that the team saw the apex of the large vent field, 750 meters east of the ridge axis, and 5 to 7 kilometers north of the active vent on the closest known axis.

Sampling of the nine vents revealed a temperature of 368 degrees Celsius, with elements whose presence indicated a higher origin temperature – a minimum of 437 degrees Celsius for the observed iron-manganese ratio.

Overall, the field covers an area equivalent to a football field, the team said. Its proximity to the fault line indicates that it is controlled by tectonic activity.

Scientists believe the vents could help regrow nearby hydrothermal ecosystems after volcanic eruptions. Two eruptions have occurred at East Pacific Rise in recent decades; one from 1991 to 1992, and another from 2005 to 2006. Others are expected to occur within a few years, the researchers said.

Wider exploration of the deep ocean floor could reveal more ventilation fields in unexpected locations, which in turn could improve our understanding of how this almost alien ecosystem works.

“Much remains to be discovered about deep-sea vents along the global mid-ocean ridge, both in terms of their location and their geological, geochemical and biological characteristics,” McDermott said.

“I hope that our study will motivate future research efforts to target off-axis mapping of areas along the crest of the global mid-ocean ridge to better quantify off-axis versus on-axis hydrothermal ventilation rates.”

This research has been published in PNAS (link not active at the time of writing).

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