New Hydrothermal Field Discovered in East Pacific Ocean

A team of researchers including Ross Parnell-Turner, a geophysicist at Scripps Institution of Oceanography at UC San Diego, discovered a hydrothermal field, named YBW-Sentry, near to where the tectonic plates spread apart on the East Pacific Rise.

The discovery on the floor of the Pacific Ocean at 2,550 meters (8,370 feet) deep could change scientists’ understanding of the impact that such ocean-floor vent systems have on the life and chemistry of Earth’s oceans, the research team said.

“Very few areas in the deep ocean have been mapped at high-resolution using deep submergence technologies,” said Parnell-Turner. “However, major discoveries can be made by collecting near-bottom bathymetry using autonomous underwater vehicles (AUVs).”

The field is about 200 miles off the coast of western Mexico, and was discovered during an expedition on Scripps Oceanography’s Research Vessel Roger Revelle in 2021. The site of the hydrothermal vent and its field covers an area equivalent to a football field, roughly twice the size of the nearest previously known active hydrothermal vents in the region. Vent chimneys resemble candelabras that are the height of three-story buildings.

The findings were published July 18 in an article titled “Discovery of Active Off-Axis Hydrothermal Vents at 9° 54’N East Pacific Rise,” in the journal Proceedings of the National Academy of Sciences (PNAS).

Deep-sea hydrothermal vents are found around the world, most often in volcanically active locations along the crest of the global mid-ocean ridge system. Magmatic activity, driven by upwelling of Earth’s mantle, creates new oceanic crust that makes up the tectonic plates. This creates cracks through which sea water percolates in crustal rocks. Much like hot springs on land, hydrothermal vents discharge mineral-rich fluids that have been heated deep beneath the seafloor.

The research that led to the discovery of the off-axis vent field along the East Pacific Rise was spearheaded by the McDermott lab at Lehigh University. The team collected fluids from the black smoker chimneys and analyzed them for their geochemical characteristics, which can indicate the temperatures at which the fluids are forming. Hotter temperatures could be a sign of an impending eruption. At the same time, the team also installed self-recording fluid temperature loggers to provide measurements every ten minutes over two-year time periods at the active vent chimneys. The temperature measurements provide a time series of the changes the vents experience. The research team has nine vents instrumented in the study area.

Near-bottom bathymetric surveys conducted by the research team between 2018 and 2021 with the AUV Sentry, provided by Woods Hole Oceanographic Institution's (WHOI) National Deep Submergence Facility, produced the high-resolution (1 meter) maps that resolve very small seafloor features, according to Parnell-Turner.

“We identified an off-axis field of tall pinnacles, and we assumed that they were either older volcanic spires or inactive hydrothermal chimneys deposited long ago,” he said.

Paper co-author Daniel Fornari, a marine geologist at WHOI, said, “We were astounded that not only was the field very active, but it is larger in area and hotter in origin temperature than any other hydrothermal vent field known along this portion of the East Pacific Rise that has been studied for the past 30 years.”

According to Lehigh’s Jill McDermott, over the past 15 years the ways in which scientists study and sample the seafloor have been revolutionized by the high-resolution maps produced by autonomous underwater vehicles. The maps generated by the AUV sonars are similar in scale to what is used in land-based geological surveying and mapping using a variety of sophisticated techniques that include drone mapping and laser scanning.

The search for active hydrothermal vents has historically focused on the trough that marks the axis and locus of most of the volcanic eruptions along the East Pacific Rise. The team has been expanding the high-resolution map west and east of this axial trough — between 9° 45-57'N latitude — for the past three years using the Sentry AUV.

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

Two previous eruptions have occurred at this site―in 1991-1992, and again in 2005-2006―and the team forecasts that the next eruption could occur within the next few years, said co-author Thibaut Barreyre, a geophysicist at the University of Bergen in Norway.

“The new vent field may seed recovering hydrothermal ecosystems after volcanic eruptions,” said Santiago Herrera, a co-author who is a biological oceanographer and faculty member in Lehigh University’s Department of Biological Sciences.

The three-year research project is funded by the U.S. National Science Foundation's Ocean Sciences Division, Marine Geology and Geophysics Program.

“There is much still left to be discovered about deep-sea vents along the global mid-ocean ridge, both in terms of where they are located as well as their geological, geochemical and biological characteristics,” said McDermott. “I hope our study will motivate future research efforts to target mapping off-axis areas along the global mid-ocean ridge crest to better quantify the extent of off-axis versus on-axis hydrothermal venting.”

Additional authors of the PNAS paper include: Connor C. Downing, Kelden Pehr and William S. Dowd in Lehigh’s Department of Earth and Environmental Sciences; Jyun-Nai Wu of Scripps Oceanography; Nicole C. Pittoors and Samuel A. Vohsen in Lehigh University’s Department of Biological Sciences; and Milena Marjanović of France’s Institut de Physique du Globe de Paris.

Adapted from Lehigh University