July 19 () –
The finding of a new field of high-temperature, off-axis hydrothermal vents on the floor of the Pacific Oceanat a depth of 2,550 meters, could change scientists’ understanding of the impact that these Ocean floor vents have on the life and chemistry of Earth’s oceansaccording to the researchers published in the journal ‘Proceedings of the National Academy of Sciences’.
A team of scientists, including Jill McDermottchemical oceanographer and faculty member of the Department of Earth and Environmental Sciences at Lehigh University, in the United States, discovered the off-axis hydrothermal field, named YBW-Sentry, in the area of the global mid-ocean ridge known as the East Pacific Rise. The study area is located more than 300 kilometers from the west coast of Mexico.
the new vent covers an area equivalent to a football field, about twice the size of the nearest active hydrothermal vents in the region. The chimneys look like chandeliers that are the height of a three-story building, they explain.
Deep-sea hydrothermal vents are found all over the world, especially in places with volcanic activity along the crest of the global mid-ocean ridge system. Magmatic activity, driven by rising currents of heat in the Earth’s mantle, causes the fragile tectonic plates that make up the crust to split.
As the plates move apart, magmatic activity and volcanic eruptions form new rocks on the seafloor. This magmatic and tectonic activity creates cracks through which seawater seeps into the rocks of the earth’s crust. Like hot springs on land, hydrothermal vents spew out a mineral-rich liquid that has been heated under the seafloor.
The research that led to the discovery of the off-axis vent field along the Eastern Pacific Rise was spearheaded by the McDermott Laboratory at Lehigh University. The team collects fluids from the black vents and analyzes them based on their geochemical characteristics, which can indicate the temperatures at which the fluids are forming. Higher temperatures could be a sign of an impending eruption.
At the same time, the team is also equipping active vent stacks with self-recording fluid temperature loggers to provide measurements every ten minutes over two-year periods. Temperature measurements provide a time series of changes in stacks. The research team has nine instrumented stacks in the study area.
Near-bottom bathymetric surveys conducted by the research team between 2018 and 2021 with the Sentry autonomous underwater vehicle (AUV), provided by the Woods Hole Oceanographic Institution (WHOI) National Deep Submergence Facility, produced the high-resolution maps. (1 meter) that resolve very small seafloor features, according to Ross Parnell-Turner, a geophysicist at the Scripps Institution of Oceanography in California, and a co-author on the paper.
“We identified a field of tall off-axis pinnacles, and surmised that they were older volcanic spirals or dormant hydrothermal vents deposited long ago.says Parnell-Turner.
For his part, Daniel J. Fornari, WHOI marine geologist and co-author of the work, acknowledges that they were surprised “that the field was not only highly active, but that it was larger in surface and hotter in its source temperature than any other hydrothermal vent field known along this portion of the Eastern Pacific Ridge that has been studied in the last 30 years.
According to McDermott, in the last 15 years, the way scientists study and sample the seafloor has been revolutionized by high-resolution maps produced by autonomous underwater vehicles. Maps generated by autonomous underwater vehicle sonars are similar in scale to those used in land-based geological surveying and mapping using a number of sophisticated techniques including drone mapping and laser scanning.
“Very few areas of the deep ocean have been mapped at high resolution using deep-diving technologies,” says Parnell-Turner. “However, great discoveries can be made by collecting near-bottom bathymetry with AUVs.”
The search for active hydrothermal vents has historically focused on the depression that marks the axis and site of most volcanic eruptions along the East Pacific Rise. The team has been zooming in on the high-resolution map to the west and east of this axial depression, between 9°45-57’N latitude, for the past three years using the NDSF Sentry AUV. McDermott describes the NDSF as the “NASA of the deep sea.”
“The mapping work provides a detailed image of the seabed so that we can control and quantify the changes that occur when the next volcanic eruption occurs along this portion of the axis of the Eastern Pacific ridge,” says McDermott.
According to Thibaut Barreyre, a geophysicist at the University of Bergen (Norway) and co-author of the study, there have already been two eruptions at this site, in 1991-1992 and 2005-2006, and the team predicts that the next eruption could occur in the next years.
“New vent field may seed recovery of hydrothermal ecosystems after volcanic eruptions“says Santiago Herrera, co-author, biological oceanographer and faculty member in the Department of Biological Sciences at Lehigh University.
“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 says. “I hope our study motivate future research efforts to target mapping of off-axis zones along the global mid-ocean ridge to better quantify the extent of off-axis versus on-axis hydrothermal vents.”
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