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Dr. Nelia Dunbar uses geochemistry to study volcanic rock and ash. She directed the electron microprobe laboratory at New Mexico Tech in Socorro, New Mexico, where she is now an advisor and adjunct faculty member. After serving as director of the New Mexico Bureau of Geology and Mineral Resources, her current role includes research and outreach. She has participated in more than 20 research trips to Antarctica to study ice cores, cylinders of ice drilled from ice sheets or glaciers.

� Chris Eboch

This interview was edited for length and clarity. 

What was your path to a career in geochemistry?

I lived overseas growing up, saw a lot of ruins, and wanted to be an archaeologist. I didn’t actually like my first college archaeology class much, but I took geology and was hooked. My research project advisor was a glaciologist studying glacial lakes with volcanic ashes. He said, “Why don’t you work on these volcanic ashes for your senior thesis?� I’m still working on volcanic ash.

What can we learn by studying ice cores?

Earth’s climate is changing, and we need to understand where it’s going. The key to the future is to look at the past. There is a very close connection between what gases are in the atmosphere and what Earth’s climate is. Ice cores trap tiny air bubbles, so you can release the past atmosphere. Then the ice itself contains a temperature record. If you analyze the geochemistry of snow, you can figure out what the temperature of that snowflake was.  

How does volcanic ash come into this?

You can see and count summer and winter layers in the ice, but they only go back 30,000 years. Anything older is too compressed. And if it didn’t snow, that won’t show up in the visual record. The volcanic ash layers give you timelines. We focus on the geochemistry of individual glass particles with an electron microprobe. The volcanic ashes are too tiny and fine-grained to date the ash layer directly, but the chemistry may tie it to a known volcanic eruption with a known age to get the timeline.

How do you collect and process ice cores?

An entire community decides where to sample, because everyone is studying different things. [In the United States,] you submit a proposal to the U.S. National Science Foundation. When funding comes through, you take a big drill rig out to wherever you’re drilling. The ice comes up in meter-long segments covering multiple years. When you get deep, the air bubbles are under pressure, and if the core gets jostled, it will explode. Each piece “relaxes� in an ice cave for a year to get used to being at the surface. A crew makes observations in the field. A lot of students are involved.

Then the cores are flown to McMurdo Station [U.S. Antarctic research station] and are then sent to the United States on a cargo ship in special freezers. Cores are divided into segments for different scientists. Most people want interior ice that hasn’t been contaminated. We can use the outside layers, the wings, for ash studies. 

Do you have advice for high school students?

If you find solving puzzles to be interesting and fun, that will be a big part of your career. What you learn will be used by many other people and will be used as a building block to move science forward. If you love being outdoors, geology may be a great fit, but there are many different careers. If people say they are not good at science, they just haven’t found the science they’re good at.