Research@Mines

The island splitting eruption of the Tonga Volcano in January caught the world’s attention with its explosive plume of ash and subsequent tsunami. Large volcanic eruptions like this can have impacts on the climate and carbon budget of earth’s atmosphere and oceans.

But some may not realize that many, if not most, volcanic eruptions on earth don’t happen on volcanic islands, rather they occur deep under water along oceanic rift zones. These rift zones are volcanic fissures that occur along tectonic boundaries where rising plumes of magma come to the surface and slowly push oceanic plates apart. The constant underwater eruptions along rift zones can also impact the amount of carbon dioxide (CO₂) in the atmosphere and ocean.

For scientists to understand and model the impacts of human caused climate change, they need to know all the sources and sinks for CO₂ - including the amount of CO₂ naturally produced by these oceanic rift zones. Better quantifying this amount can yield improved understanding of the impacts of anthropogenic climate change.

South Dakota Mines Assistant Professor and principal investigator Gokce Ustunisik Ph.D., and co-principal investigator Roger Nielsen, Ph.D., in the university’s Department of Geology and Geological Engineering are leading a new $654,105 National Science Foundation funded research project to quantify the amount of CO₂ produced in mid-oceanic rift zones. The research, led by Mines, is being undertaken in conjunction with Woods Hole Oceanographic Institute (WHOI) of Massachusetts Institute of Technology.

To achieve their research goal, Ustunisik and Nielsen will study the amount of dissolved CO₂ content of tiny melt pockets – melt inclusions trapped in minerals from the rocks produced by underwater eruptions and collected from the ocean floor.

“Our project looks at CO₂ dissolved in the magma. We look at the content in tiny pockets of melt captured in crystals formed in cooling magma that makes up oceanic crust. This kind of crust make up 70% of the Earth’s crust,” says Nielsen.

“The Earth’s mantle is the largest reservoir of carbon on the planet, but it’s also among the least studied and constrained. The current estimates for the amount of carbon produced by oceanic rift zones and stored in the mantle vary greatly. Scientists who want to accurately model future climate change need to know how much carbon is produced by these earth systems” Ustunisik adds.

“The equivalent would be if you were a business owner, and you ignored your taxes or Social Security payroll obligations as part of your expenditures. This would be ignoring an important component in your balance sheet,” says Nielsen.

But rocks from the depths of the ocean are not easy to come by. Dr. Ustunisik and her graduate students at Mines will be using rock samples collected from all over the world over the past 40 years, during multiple missions by submarines, robotic submersibles and ocean dredging. The experimental petrology laboratory run by Ustunisik at Mines will collaborate with microanalytical laboratories at Woods Hole and Oregon State University to analyze parts of the recently formed rocks to better quantify how much CO₂ these rift zones produce.

“We are looking at what are called zero age lavas,” says Nielsen. “So, these are very, young rocks formed inside mid-oceanic ridges where the plates are separating,” says Ustunisik.

While the estimates vary widely, Nielsen says it’s possible the amount of CO₂ produced annually along mid-oceanic rifts is about the same as the amount of extra carbon produced by human emissions each year. He says the input from the earth varies dramatically from year to year, but is not increasing at the same rate as human emissions.

“We need to understand the base level produced by the earth. The human emissions on top of the natural CO₂ production leaves us less and less wiggle room,” says Nielsen. “We also need to understand the potential impacts of infrequent events, like volcanoes, on top of human caused greenhouse emissions. What we are really trying to do is build accurate predicative models.”

The team will also be working with students at both Mines and Oglala Lakota College to undertake the experiments and analysis that will gather the data needed for the overall study. This project involves efforts for developing analytical infrastructure, teacher training and research projects for undergraduates in partnership with Oglala Lakota College.

Ustunisik and Nielsen point out that an initial investment of $50,000, from a South Dakota Board of Regents competitive faculty research grant awarded to Ustunisik formed the foundational research needed to secure this NSF funding. “The BOR seed money for our research was essential in our success,” she says.