From the Field: 'Trail by Fire' Takes Geoscientists on a Rugged Tour of South American Volcanoes


A team of six young researchers led by Yves Moussallam, a research fellow at Scripps Institution of Oceanography at University of California San Diego, will visit 15 active volcanoes in Peru and Chile over a three-and-a-half-month period beginning this week. Their ultimate goal is to better understand how volatile gases in the atmosphere and hydrosphere are recycled through Earth’s crust and mantle at subduction zones.

An expedition of the scope and scale of “Trail by Fire” has never before been attempted, said Moussallam.

“The atmosphere that allowed our planet to spark and sustain life formed as a result of gases emitted by volcanoes early in Earth history,” he said. “One of the outstanding questions with profound implications for the Earth system regards how much of the subducted volatile gas is released back to the atmosphere, and how much remains trapped at depth”.

Volcanic gases, mainly water and carbon dioxide, are constantly recycled back into the deep Earth at subduction zones where tectonic plates sink into the mantle. During this process, the sinking plate, subjected to increasing heat and pressure, releases volatiles which, added to the mantle, induce melting and fuel volcanic explosions, completing the cycle. While this depiction of the earth system is well established conceptually, the actual flux of volatiles in and out of the deep Earth remains poorly quantified.

The researchers chose a region with some of the world’s most active subduction-related volcanoes and will travel the length of half a continent from Peru to the southern tip of Chile conducting state-of-the-art measurements to characterize gas emissions of every degassing volcano on the way.

“Gas measurements on active volcanoes have been performed for many years but never at such scale and this expedition will provide the first data on many volcanoes never studied before,” said David Hilton, a professor of geochemistry at Scripps. “It is a very ambitious and remarkable undertaking.” 

Because only a fraction of active volcanoes are permanently monitored, a large gap remains in scientists’ knowledge of what volcanoes add to the chemical mix of the atmosphere. Moussallam says that one goal of ‘Trail by Fire’ is to better characterize this volcanic contribution. Such data are critically needed as they constitute one of the largest sources of uncertainty in climate models.

The researchers will be traveling among the volcanoes in a specially outfitted vehicle, the use of which was awarded to them by a bursary administered by the United Kingdom’s Royal Geographical Society and funded by automaker Land Rover.  As part of the award, a Land Rover Defender was modified to fit the scientific equipment and provide extra battery storage, transforming the vehicle into what the scientists have dubbed the first 4x4 mobile volcano observatory.

The team’s suite of instruments will enable first-of-their-kind measurements. For instance, a newly developed “Delta Ray” portable laser spectrometer will be able to determine the isotopic composition of carbon in the field as opposed to having to collect samples for analysis back in the lab.

In addition, drones operated by the scientists will fly both underneath and inside volcanic gas plumes to measure the flux and composition of gases remotely.

“Such measurements would be the first of their kind and allow us to perform accurate measurement even when the plume is unattainable by ground or the volcanic activity too high for safe ascent,” said team member and drone specialist Aaron Curtis from the New Mexico Institute of Mining and Technology.

With the support of NASA scientists, satellites will track the team’s progress along the Andes, with team data being used for ground-truthing satellite measurements, allowing for their observations to be extrapolated spatially and temporally.

The South American Andes range is one of the most active segments of the “Ring of Fire” tectonic borderland that surrounds the Pacific Ocean. As evidence, two earthquakes both exceeding magnitude 8 have struck Chile in the past four years and the country was the site of the largest earthquake in recorded history, a magnitude 9.5 event in 1960.

The other expedition members are Nial Peters of Cambridge University (United Kingdom), Talfan Barnie of The Open University (United Kingdom), Ian Schipper of the Victoria University of Wellington (New Zealand), and Philipson Bani of the Institute of Research for the development (Indonesia and France).

Additional support for the expedition came from the Deep Carbon Observatory and a number of other companies that supplied scientific instruments, safety equipment, and logistical support.

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