The Queen of Wind-Blown Sediments: Kelly Deuerling’s Aeolian Geochemistry (Women in Science 53)
Life is an ion-hungry enterprise. Sure, carbs, proteins, and fatty acids get most of the press, but without a steady stream of calcium to help regulate signal transduction in cells, zinc to promote proper growth, iron for oxygen transport, and a host of other minerals besides, things start going very wrong for living systems. We need minerals, but how do we get them? How is it that they move themselves around the Earth?
For areas high in precipitation, there is a ready answer – ions dissolved in rain water are deposited wherever the water falls, but what about places where rain is comparatively rare? The answer, it turns out, lies in one of the great unsung heroes of world ecological and geological history. Dust. Or, more precisely, dust and wind, and among those working to uncover the extent to which physical weathering and aerial dust transportation shape our world is the University of Florida’s Dr. Kelly Deuerling.
She was born in Tallahassee, Florida, in 1985, and divided her youth between books and nature, her geologist father making sure that the family took two weeks out of each year to go explore the natural phenomena of different parts of the country, constantly stopping the car on the way to and from their ultimate destination to check out any geological sites that looked promising.
It doesn’t get much better, as a kid, than to tromp along next to a parent who is genuinely excited about something, and willing to include you as an observer or even deputy in that passion. Small wonder, then, that Deuerling naturally gravitated to science in high school and, while in college at the University of Florida, she found her passion for the precise minutiae of geochemistry. She loved the “tedious/technical protocols and instrumentation” just as much as the field work, the hours upon hours of getting soil samples to offer up their compositions and thereby tell their geological tales.
As an undergraduate, she studied Floridian aquatic geochemistry, sediment provenance in Alaska, and magma evolution of a million year old eruption in Dominica. That is, already, objectively cooler than anything any of us Norms have done or will do. But her Master’s work at Ohio State was several orders of magnitude cooler still. Quite literally, as her thesis involved a scientific expedition to Antarctica to quantify the mechanisms of mineral recycling in the McMurdo Dry Valleys, or MDV. These are plains of brutally low temperature but also incredibly low precipitation. Most of the snow that falls sublimates (turns directly to gas) instead of melting, and so the question becomes, how do the aquatic systems found in the lakes of the MDV get their minerals?
Deuerling describes her work as, “Basically, I walked around at the bottom of the Earth for about a month and collected dirt and loved every second of it!” That is a modest understatement. Yes, she collected samples of the sediments that had been blown onto the lakes and plains, but then she also had to analyze those sediments and compare the compositions to the minerals found in the surrounding geological formations, and then, since she couldn’t just hang around for a year and observe the seasonal fate of these deposited sediments, she had to recreate the leaching of her specimens in the lab.
Her analysis of the composition of the sediments revealed that they were overwhelmingly locally derived, the result of dust swept from the Antarctic hills onto the plains, rather than deposits from the massive amounts of dust blown into the global ecosystem from the world’s major desert systems. While other geologists are discovering more each day about how pervasive wind-blown desert sediments are, how dust blown off the Sahara Desert finds its way to California, Deuerling was able to ascertain that in Antarctica, they keep it local. Dust from Antarctic mineral sources gets blown down into the valleys, and then lands on the frozen lakes.
But what happens to it then? That involved recreating a season in the lab, including the two major events of an Antarctic year, melting and freezing/thawing. What happens when you try and dissolve the sediments in newly melted ice, and what happens when you freeze them and then let them thaw again? She quantified how much of the mineral continent of those sediments leaches its way into the aquatic system, and provided thereby the mineral link between the mountains, the wind, and the water, the workings of a massive geologic recycling program founded on dust.
Her studies of the recycling of minerals through wind-blown sediments resulted not only in the first quantification of this Antarctic system, but in one of the all time great stories of scientific romance, about how Deuerling met her husband, Rich Jenkins. I’ll let her tell it.
The BBC had just finished filming “Frozen Planet” the second year I went to Antarctica and they threw a wrap party for town. I was in attendance and ended up conversing extensively with Sir David Attenborough, THE voice of natural science. After being whirled around the room and introduced to more people than I could hope to remember, we ended up back by the entrance. Just then, the assistant lab supervisor for Crary Lab (McMurdo’s science facility), Rich Jenkins, came in and Sir David lit up. He brought me over and said, “Rich, Rich! Have you met Kelly, the Queen of Windblown Sediments?”
Rich, slightly confused and elated by the fact that Sir David Attenborough knew his name, replied, “Why yes, Sir David, I have!”
“Capital! Go get her a mimosa!”
And I was handed off to Rich with the blessings of nobility.
After wrapping up her work at Ohio State on Antarctic sediments, it was back to the University of Florida to get her PhD, this time studying, perhaps inevitably, the other awesomest place on Earth, Greenland. Here, her question was, how does physical weathering promote chemical weathering? Chemical weathering includes processes like oxidation and hydrolysis that break down a rock’s chemical bonds. Those work a good deal better when the surface area is high. Deuerling hypothesized that those areas of a rock’s structure that are subjected to the grinding of glacier advance and retreat would, as a result, have a higher surface area (the grinding reducing the rock to a kind of geologic “flour”) and therefore higher rates of chemical weathering despite the low temperatures, which ties also into the relation of glacial events to carbon dioxide release and therefore global warming.
Once the Greenland samples were collected, the arduous but satisfying task of analysis began. “We spend days sending samples that have been dissolved using concentrated hydrofluoric acid through a series of columns filled with exchange resins that isolate our elements of interest. It takes a minimum of 4 days to isolate all the elements and you can run up to 12 at once. I collected over 120 samples when I went to Greenland in 2013 and I only finished analyzing them about a month ago!”
Geochemistry lies at an interesting intersection of interests. It has the rough and tumble fieldwork of ecology, the minute and precise labwork of chemistry, and the big questions where time is measured in hundreds of millions of years of astronomy. There is the romance of looking at a soil composition and imagining the massive world-spanning processes that caused it, and the steady pragmatism of ensuring proper collection procedures and chemical analysis. It takes a rigorous dreamer, a Dr. Kelly Deuerling, and if you’re one such, the world is large, and full of dust, and silt, and rock, all of which have been waiting for millions of years to tell their secrets.
FURTHER READING AND DOING: Here is Kelly’s list of awesome things to read and neat apps to pick up to make your walking life a bit more geologic in scale:
1) Bill Bryson’s “A Short History of Nearly Everything”
2) John McPhee “Annals of the Former World” (which I am just starting, but it’s worth it!)
3) “Roadside Geology of {insert state here}”. I would not recommend reading these, but actually living them. Pick up one for your state and see what is around you! If your family travels a lot, there is a new app called “Flyover Country” that allows you to download geological and paleontological information about the route you are taking. Both of these are awesome because they give you the geological context of what is going on around you.
