Deep-sea Exploration Of Underwater Volcanic Eruption Reveals "Some Of The Newest Seafloor On Earth"

The remotely operated vehicle Deep Discoverer explores a conical eruptive center at the top of one of the newly discovered lava flows. Bill Chadwick, NOAA Exploration and Research Program and Pacific Marine Environmental Laboratory

An accidental discovery has led scientists to some of the newest seafloor on Earth, and let’s just say the photos look as though they've captured something from out of this world. The team wasn’t looking for the deepest known volcanic eruption on the planet. Rather, they were searching for new hydrothermal vents just off the Mariana Trench. 

“One reason we’re interested in this area is because deep-sea eruptions provide heat for these hot springs and hot springs provide chemical energy for really unusual ecosystems that live around hydrothermal vents,” lead author and marine geologist Bill Chadwick explained to IFLScience. Although the scientific community has been aware of these hydrothermal vents since the 1970s, less is known about the different kinds of animals that live around them.

The Mariana area is particularly interesting because there are hydrothermal vents in two different environments that have contrasting chemistry and are home to different animals. Here, the plan was to compare organisms that live in the Mariana back-arc against those found in the Mariana arc – two ecosystems that run parallel to each other but exhibit different oceanic conditions. Instead, the team came across a recent volcanic eruption about 4,500 meters (14,700 feet) below the surface, which has formed volcanic glass structures. They also spotted a few organisms moving into their new home.

“Most of Earth’s volcanic activity actually occurs in the deep ocean but it almost always happens undetected and unseen,” said Chadwick.

In the last 30 years, scientists have used innovative exploration methods to document about 40 undersea eruptions – before 1990, none had been detected. Chadwick and his team discovered the eruptions thanks to a combination of luck and having the right tools to be able to detect them.

When the team first arrived on the scene in 2015, they observed venting indicative of new lava that was still warm. When they returned the following year, this venting had subsided considerably. After comparing this data with bathymetric data collected in 2013, the team determined the eruption had likely taken place just a few months before their initial arrival, stretching 7.2 kilometers (4.5 miles) in length and ranging in thickness from 40 to 137 meters (130-450 feet).

Chadwick said discoveries like this one can tell us more about how volcanoes behave on land and how underwater eruptions impact the ocean around them.

“Since we can’t really detect most eruptions when they’re happening, every time we find one it’s kind of a rare opportunity to learn about rare eruptions, how they work, and what kind of impacts they have on the surrounding ocean,” he said.

The full study, along with more incredible deep-sea photos, is published in a special issue of Frontiers in Earth Science.  

Edge of new lava (darker at the bottom) flowing over older sedimented seafloor (lighter at the top) photographed in the Mariana back-arc. Bill Chadwick, NOAA Pacific Marine Environmental Laboratory, Woods Hole Oceanographic Institution, and Schmidt Ocean Institute

Very glassy lava flows less than 3 years old discovered in the Mariana back-arc. Bill Chadwick, NOAA Exploration and Research Program and Pacific Marine Environmental Laboratory

The rover's arm (a), a polychaete or "bristle" worm (b), and a shrimp (c). The squat lobster (d), which only lives around hydrothermal vents, is one of the early colonizers of the new lava flows erupted in the Mariana back-arc. Chadwick et al./Frontiers in Earth Science
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