Submarine volcano spits sulfur and gases

Researchers are observing eruptions for the first time from close range

Submarine volcano Rota-1 © NOAA / PMEL
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A "yellow, pulsating plume of smoke with properties unlike any observed so far" - so researchers in an international team of scientists describe now in "Nature" their observations of a submarine volcanic eruption near the Mariana Islands northwest of Guam. As close as before, they were eyewitnesses of the eruption.

The scientists around Robert Embley, geophysicist at the Pacific Ocean Marine Environmental Laboratory of the US Marine Research Agency NOAA and Bill Chadwick, volcanologist at Oregon State University, had been monitoring the eruptive activity of the Northwest Rota-1 baptized volcano in several expeditions since 2004, including using a remote-controlled underwater robot, His recordings provided the closest direct images of an undersea eruption ever.

Several times during this period, eruptions occurred in an active crater, "Brimstone Pit", on the south side of the volcanic peak 550 meters below the water surface. Large clouds of sulphurous liquid and puffs of volcanic ash were ejected. According to the researchers, this activity suggests that this type of deep-sea volcanoes appears to have longer eruptions than other subsea volcanoes located on mid-ocean ridges.

On "close contact" with the eruption

"We had to repeatedly rescue our remote-controlled submersible 'Jason II' several times to prevent it from being trapped by the volcanic clouds, " Chadwick reports. "But at other times we were able to observe the eruption from only three meters away - something that would never be possible in the countryside. In some ways, therefore, we were able to see the processes more clearly at the bottom of the ocean than in the dry land. That was surprising. "

The Mariana Islands - Part of the Pacific Ring of Fire © NOAA / PMEL

In addition to the sulphurous clouds of liquid and ash, which fluctuated in intensity and volume, the volcano also hurled volcanic "bombs", structures of semi-molten sulfur and boulders of up to 15 centimeters in diameter, which flew up to 50 meters above the crater. In particular, the 2006 expedition was, as the researchers describe, "breathtaking": "We saw species of volcanic activity that had never been directly observed before, including lava explosions from a crater accompanied by red glow It's the heightening of gas and rock, "explains Embley. display

Sulfur lights and teeming life

In another volcano, Daikoku, in the northern part of the Marian volcanic arc, scientists discovered a cloud of molten sulfur 420 meters below the water's surface. Its temperature was 187 degrees Celsius. "It was a sulfur tern with a flexible crust that moved in a wave, " explains Chadwick. The movement was triggered by gases that rose continuously from the depths below the pool and migrated through the sulfur. It was a captivating sight

But life was also found in depth: The scientists discovered extensive bacteria mats and hydrothermal animals on Rota, including two different species of crab, which lived in places at a density of up to 200 animals per square meter. At least one of them evidently fed on dead fish, which, killed by the poisonous volcanic gases, sank down from the middle water range. In particular, the "black smokers" lying near the submarine volcanoes are considered by researchers to be a possible model of primeval life on earth.

(Oregon State University, May 30, 2006 - NPO)