Researchers have determined magma is wetter than previously thought.

Volcano experts knew volatiles in magma play an important role in influencing the size and power of an eruption. But measuring volatile levels is difficult. In the wake of a violent eruption, all the volatiles have evaporated and escaped into the atmosphere.

The best technique scientists have for measuring volatile levels is locating and analyzing tiny bits of magma trapped in crystals ejected during the eruption. By measuring the amount of hydrogen in the magma inclusions, researchers can estimate the amount of water that was dissolved in the magma prior to the eruption.

Scientists have accepted the technique as a reasonable way to determine the lower limit of volatile levels in a volcanic magma. But researchers at Washington University in St. Louis wanted to establish an upper limit.

"What people have never looked at before and what we're trying to measure now is, how big is this bucket?" Michael J. Krawczynski, assistant professor of earth and planetary sciences, said in a news release. "You can imagine if it rained a lot, and your rain gauge was full, then you don't really know how much it rained. It could have rained more! We just can't say."

Similarly, if a melt inclusion is too small to hold all the water dissolved in the magma, then scientists aren't measuring the upper limit of volatile levels.

Researchers took to the lab to test how much water a melt inclusion can hold. To create a synthetic melt inclusion, scientists replicated the conditions of a magma chamber, complete with high temperatures and extreme pressure. They melted and rapidly cooled a magma sample, confirming that glass formed. Scientists repeated the process, adding more water each time until the rapid cooling failed to form glass.

"We found out that if you have a lot of water, then eventually you don't have a glass," said Maxim Gavrilenko, a former postdoctoral fellow in Krawczynski's lab, now a researcher at the University of Nevada.

Non-glassy melt inclusions are relatively common, but they are rarely studied by scientists. The authors of the latest study -- published this week in the journal American Mineralogists -- suggest this bias has prevented scientists from accurately modeling volatile levels inside volcanoes.

"If the deep magmas in these zones have more than 9 weight-percent of water, then they won't be correctly measured by the current gold-standard method," Gavrilenko said. "There is a need to find a new method for how to measure. We need a new, bigger bucket."

The findings could force researchers to reconsider the amounts of water being absorbed into the mantle at subduction zones.

"If more is going down into the mantle, more needs to be coming out back into Earth's crust," Krawczynski said. "That's what we're looking at here. We've understood that it's a cycle that needs to be balanced, but we haven't had a good grasp of the sizes of the different reservoirs."

Related Links
Bringing Order To A World Of Disasters
When the Earth Quakes
A world of storm and tempest

Tweet

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only

Papua New Guinea deploys army to help volcano emergency
Kokopo, Papua New Guinea (AFP) June 28, 2019
Troops have been sent to help thousands of people displaced by a volcanic eruption on a remote archipelago in Papua New Guinea, the prime minister said Friday, as a second volcano erupted. Lava and ash flows from Mount Ulawun - one of the world's most hazardous volcanoes - have subsided, but between 7,000 and 13,000 people are believed to have been displaced and a state of emergency has been declared. "We will mobilise the military to go in and assess the situation, and we will despatch the mi ... read more