Underwater volcanism and hydrothermal vents important in carbon cycle
The nature of hydrothermal activity at ‘petit-spot’ volcanoes have not been revealed at all. Now, scientists reveal that petit-spot hydrothermal activity occurs on the deepest seafloor known to date and could release carbon dioxide (CO2) and methane, which may have implications for the global carbon cycle
Underwater volcanism on the Earth’s crust are active contributors of many different elements to the oceanic environment.
Hence, they play an important role in biogeochemical and chemosynthetic cycles of the ocean.
Although there have been many studies on high-temperature hydrothermal systems in the mid-ocean ridge — a series of underwater volcanoes that trace the edges of the different oceanic plates — there is little information on low-temperature hydrothermal systems in other volcanoes, such as “petit-spot” volcanoes.
Petit-spot volcanoes are small volcanoes that are found around the world, in regions where oceanic plates flex. Recent studies in the east of the Japan Trench have found that petit-spot volcanoes erupt alkaline magma that is enriched in carbon dioxide (CO2).
These volcanoes also produce a volcanic rock called peperite that results from the heating of water-rich sediment, which implies hydrothermal fluid production and methanogenesis. Thereby, it is suggested that petit-spot volcanoes may vent hydrothermal fluids containing methane.
These findings indicate the need for a better understanding of the hydrothermal activity of petit-spot volcanoes to properly evaluate their contributions to marine biogeochemical cycle.
In a recent study, a team of scientists, including Assistant Professor Keishiro Azami from Waseda University, investigated hydrothermal deposits from a petit-spot volcano at a water depth of 5.7 km in the Japan Trench in the western North Pacific Ocean.
“The submarine hydrothermal activity we have described in our paper is the deepest known to date. Based on our findings, we have further estimated the hydrothermal interactions that occur in petit-spot volcanoes,” explains Azami.
The research team also included Dr. Shiki Machida from Chiba Institution of Technology and Associate Professor Naoto Hirano from Tohoku University. The paper has been published in Communications Earth & Environment.
As a part of their study, the team analyzed the chemical and mineralogical composition of dredge samples obtained from the oceanic floor near the petit-spot volcano.
They found that the samples were primarily composed of iron (Fe) and manganese (Mn) oxides, and that their characteristics were attributed to hydrothermal origin, i.e., the Fe-Mn oxides precipitated directly from hydrothermal fluid.
These results indicate petit-spot hydrothermal activity as the reason for the formation of these oxides and the petit-spot volcano as the deepest hydrothermal site known to date. The researchers also found that the chemical and mineral compositions of the samples were indicative of low-temperature hydrothermal activity.
The researchers then performed x-ray fluorescence spectroscopy to identify the elemental distribution of the sample cross-sections and performed independent component analysis on the elemental distribution data to elucidate the formation process of these Fe-Mn oxides.
Their findings suggested that the formation of these Fe-Mn oxides starts when petit-spot magma produces low-temperature hydrothermal fluid, which flows up via the sediment column and precipitates Mn oxides at the interface with seawater.
This Mn oxide layer, which contains silicate debris, then grows downwards toward the seabed as more Mn oxide is deposited. Eventually this debris is altered. Next, Fe oxides are deposited via the same action on the interface between the low-temperature hydrothermal fluid and the Mn oxides.
A hydrogenetic rim then grows on these deposits at the surface that is exposed to seawater, after the cessation of hydrothermal activity.
“Based on previous research, we can estimate hydrothermal fluid from petit-spot volcanoes to be enriched in CO2 and methane compared to that from the mid-ocean ridge,” explains Azami. “This means, in turn, that the elemental contributions from petit-spot hydrothermal activity around the world may potentially have important implications for global biogeochemical cycles, in particular the carbon cycle.”
These findings underscore the presence of hydrothermal activity in cold and old oceanic plates and highlight the need for further studies on petit-spot volcanoes.
See more here sciencedaily.com
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Kevin Doyle
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Dear Science Daily,
Thank you for stumbling upon the truth. The last sentence of your article, “These findings underscore the presence of hydrothermal activity in cold and old oceanic plates and highlight the need for further studies on petit-spot volcanoes.”
“Highlight the need for further studies” means: Let’s take someone else’s tax dollars and piss them away on pointless ‘research’!
If any of you folks at ‘Science Daily’ understood actual science, you would comprehend that CO2 and methane have ZERO effect upon air temperatures in the atmosphere!
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Richard Greene
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They understand science, Mr. Doyle, but you don’t.
In addition, there are very few active volcanoes on this planet. No one knows how much heat they release, although underwater volcano heat releases can not be measured a mere 100 yards away. And no one knows the trend of CO2 emissions from the underseas volcanoes. The result is insufficient data to make ANY claims about active volcanoes, except one: It is unlikely they contribute more than 1% to 2% of the CO2 emitted each year.
More important, even with volcanoes emitting CO2, nature, which includes oceans, are still major CO2 absorbers. That means the +2.5pppm CO2 increase every year is ENTIRELY from manmade CO2 emissions.
The effect of CO2, methane and water vapor has been easured in laboratories and the results are in the MODTRAN and HITRAN databases, used by scientists, Including “skeptic” scientists, on our side, to make the claim that CO2 above the current 420ppm is A WEAK GREENHOUSE GAS THAT CAN NOT CAUSE MUCH MORE GLOBAL WARMING, SO MORE CO2 SHOULD NOT BE FEARED. Your claim that CO2 and methane do nothing ignores the work of at least 99.9% of the scientists living on this planet. Why do you think you know better?
Now you know some real climate science. You can thank me later.
CLAIMING CO2 DOES NOTHING IS JUST AS WRONG AS CLAIMING CO2 DOES EBE EVERYTHING.
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Herb Rose
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Hi Richard,
You make the same mistake that lost “scientists) make in only looking at evidence that supports your existing belief. CO2 and methane o nothing to the heat flow in the atmosphere. As Angstrom’s argument to savant pointed out (And caused Svanti to withdraw the GHGT) it is water that controls the temperature of the atmosphere.It takes 600 calories to evaporate 1 gram of water so each liter of rain that falls represents 600,000 calories of heat transported from the surface into space. Considering how much water there is on the planet, do you really believe a gas in the atmosphere (whose ability to absorb or alter the flow of heat is non-existent) at a concentration of .004% in the atmosphere can play any role in the regulation of temperature?
Herb
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MattH
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Hi Richard Green.
Geologists know a little about the history of elemental and molecular influences on earth’s climate through atmospheric, oceanic, and geologic processes.
Whilst there could be percentage errors in some statements in this year’s presentation by Dr. Ian Plimer (a geologist) the fundamental concepts are pretty reliable.
The heat flow map at 17 minutes of the above video is specifically relevant to this article.
https://coralreefwatch.noaa.gov/data/5km/v3.1/current/animation/gif/ssta_animation_90day_large.gif
Good Luck.
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