By Charles Q. Choi, OurAmazingPlanet Contributor Oct 20, 2011 12:12 PM ET
An underwater volcano bursting with glowing lava bubbles — the deepest active submarine eruption seen to date — is shedding light on how volcanism can impact deep-sea life and reshape the face of the planet.
Submarine eruptions account for about three-quarters of all of Earth's volcanism, but the overlying ocean and the sheer vastness of the seafloor makes detecting and observing them difficult. The only active submarine eruptions [ http://www.ouramazingplanet.com/underwater-volcano-erupts-1848/ ] that scientists had seen and analyzed until now were at the volcano NW Rota-1, near the island of Guam in the western Pacific.
Now researchers have witnessed the deepest active submarine eruption yet. The volcano in question, West Mata, lies near the islands of Fiji in the southwestern Pacific in the Lau Basin. Here, the rate of subduction — the process in which one massive tectonic plate dives under another, typically forming chains of volcanoes [ http://www.ouramazingplanet.com/secret-behind-formation-of-volcanic-ring-of-fire-found-0644/ ] — is the highest on Earth, and the region hosts ample signs of recent submarine volcanism.
A jumbled pillow lava forms at the base of Hades vent at West Mata submarine volcano. Credit: Joseph Resing
Surprising explosive eruption
Scientists discovered West Mata in 2008 during a survey of the northeast Lau Basin. Explosive eruptions were seen in the following year there using a remotely operated underwater vehicle — the first eruption was called Hades, the second Prometheus, both occurring at a depth of approximately 3,900 feet (1,200 meters). [Infographic: Tallest Mountain to Deepest Ocean Trench [ http://www.ouramazingplanet.com/infographic-tallest-mountain-to-deepest-ocean-trench-0249/ ]]
The nearly continuous eruptions generated spectacular incandescent gas-filled bubbles of lava up to 3 feet (1 m) wide. Gas flowing through the glowing lava could sometimes look flame-like in appearance, scientists said.
"It was absolutely stunning and exciting, something we'd never seen on the seafloor before," researcher Joseph Resing, an oceanographer at the University of Washington in Seattle, told OurAmazingPlanet. "People were just ecstatic."
Shrimp feed on microbes from diffuse venting within tens of meters of eruptive activity. The metal wand is collecting the diffuse fluids. Credit: Joseph Resing
The rich soup of chemicals these eruptions spew out helps fuel communities of deep sea organisms at West Mata. For instance, the researchers witnessed shrimp colonies grazing on mats of microbes on the rocks. Deep-sea volcanism such as this might have nurtured the first life billions [ http://www.livescience.com/16580-mud-volcanoes-life-ingredients-greenland.html (below)] of years ago — "we might see the same ingredients here as the ones used to make the first organic molecules on Earth," Resing said.
This submarine eruption is the deepest seen yet, about 2,200 feet (700 m) deeper than NW Rota-1. This was deeper than scientists had expected to see explosive eruptions. Water pressure goes up the further down you go, "so as pressure goes up, the ability of gas as it comes out of magma to cause explosions is diminished, and the thought was that you wouldn't get explosive eruptions below about 1,000 meters (3,300 feet)," Resing said.
Explosive eruption at Prometheus vent on West Mata submarine volcano. The white smoke is sulfur. Credit: Joseph Resing
Questions left
Eruptions at centers of ocean floor spreading — where the majority of eruptions on Earth happen — generally seem to occur in relatively short episodes lasting hours to months, but West Mata appears to have erupted near continuously since it was first observed in 2008. This might be because magma is focused there, instead of being spread across many volcanoes at once. "However, this is a question that we don't currently know the answer to," Resing said.
Samples the researchers gathered from West Mata revealed the volcano is spewing out boninite, a kind of water-rich lava never before seen, newly made and hitherto only unearthed in ancient deposits. Boninite is always linked with subduction zones, and these pristine samples could help yield new clues about subduction, especially its early stages. Subduction plays a key role in shaping the face of the planet [ http://www.ouramazingplanet.com/undersea-volcano-expedition-1122/ ] by consuming and recycling material from the oceanic plates.
"One thing about the deep sea is that we still don't have the best idea of what's going on down there," Resing said. "The overlying ocean and its vast size makes it a relatively unexplored place [ http://www.ouramazingplanet.com/ocean-deep-mysteries-exploration-2063/ ]. I'd like to continue exploration of the seafloor — I'd like humanity to know what else is on planet Earth and what else we can learn about it."
Resing and his colleagues detailed their findings online Oct. 9 in the journal Nature Geoscience.
Ancient Mud Volcanoes Perfect for Early Life, Rock Study Suggests
Early archean serpentine mud volcanoes in Isua, Greenland. CREDIT: PNAS/Marie-Laure Pons, et al.
Charles Choi, LiveScience Contributor Date: 17 October 2011 Time: 03:00 PM ET
Ancient deep-sea mud volcanoes may have been ideal settings for early life on Earth, researchers suggest.
Life may have first developed on Earth nearly 4 billion years ago, but much remains mysterious about its beginnings. To learn more about life's origins [ http://www.livescience.com/13363-7-theories-origin-life.html ], scientists investigated some of the oldest remnants of crust on Earth — rocks 3.7 billion to 3.8 billion years old from Isua on the southwestern coast of Greenland.
The researchers found these ancient rocks once were permeated with lukewarm alkaline fluids rich in carbonates. These liquids resemble those seen today in so-called serpentine mud volcanoes [ http://www.livescience.com/3461-otherworldly-scenes-seafloor.html ] located in the deep sea near the Mariana Islands, an archipelago in the Pacific Ocean formed by the summits of volcanoes; the conditions would have made the area off the coast of Greenland an especially friendly place for amino acids, helping keep them stable in the distant past. Amino acids are key ingredients of life, serving as the building blocks of proteins.
"These serpentine mud volcanoes would have been the best environment for sustaining life," researcher Francis Albarede, a geochemist at the Ecole Normale Supérieure of Lyon in France, told LiveScience. "These findings mean that you could have sparked life at those places and also have it survive there."
Scientists have long thought that life might have begun at deep-sea hydrothermal vents [ http://www.livescience.com/24-volcanic-origin-life.html ] typically found near volcanically active locales. These are rich in chemical and thermal energy, often helping sustain vibrant ecosystems. However, the vast majority of hydrothermal vent fields seen now are too hot and too acidic for a soup of free-floating amino acids to have survived.
"It'd be like trying to make life evolve from hot Coca-Cola," Albarede said. In contrast, serpentine mud volcanoes are relatively lukewarm, and alkaline instead of acidic.
Although these serpentine mud volcanoes are relatively uncommon now, they would have been more prevalent when the seas more thoroughly dominated the world. They seem to prefer to form at oceanic subduction zones [ http://www.livescience.com/16233-primordial-gases-deep-earth-reveal-planet-formed.html ] — that is, areas where oceanic plates dive under one another. Nowadays, subduction zones are mostly located at the borders of continental plates instead.
As to why serpentine mud volcanoes prefer to form at oceanic subduction zones, "that's an issue people haven't figured out yet," Albarede said.
Albarede and his colleagues detailed their findings online Oct. 17 in the journal Proceedings of the National Academy of Sciences.
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