From Arizona’s aquifers to the Western Tiers

Chris Eastoe grew up on a farm along Illawarra Road outside Longford, and for much of his adult life that was about as close to Tasmania as his career would get. He spent his professional years at the University of Arizona in Tucson, where he became one of the world’s leading isotope geochemists, mapping the hidden plumbing of desert aquifers, pioneering new techniques in chlorine isotope analysis and running a carbon dating laboratory that could reach back through centuries of geological time.

The work that defined those decades was far from abstract. Tucson sits atop a vast alluvial basin that, until Colorado River water became available, was the city’s sole source of drinking water. With a population approaching a million people, understanding that underground resource was not a trivial matter. Eastoe and his students used isotopes of oxygen, hydrogen, sulfur and carbon to trace exactly where the water came from, how old it was, and how it moved through the basin beneath the city. “Water comes in from different creeks in different corners of the basin,” he says, “and you can actually trace how it flows through.”

That work expanded into a cross-border project around El Paso and Ciudad Juárez, the sister cities straddling the Rio Grande, and into a study of chlorine isotopes in salt-bearing geological formations that Eastoe regards as pioneering. Among his most unusual projects was completing a decades-long study begun by his colleague Professor Paul Damon, who died before the project was completed. The work involved 500 sequential carbon-14 measurements taken from a sequoia tree spanning roughly 1000 AD to 1500 AD. Because carbon-14 levels in wood function as a proxy for solar activity, the data offered a rare long-term window into how the sun’s behaviour translated into climate effects. One finding still puzzles him: a lag between peaks in solar activity and the corresponding climate response in the region where the tree grew. “At a thousand-year timescale, the heating from a peak would actually be delayed by one or two centuries,” he says. The implication, still contested among researchers, is that some additional solar-induced warming may eventually compound what humans have already set in motion.

He also spent years cultivating research links with China and India, including a doctoral student who made a 36-hour train journey through the mountains from Guiyang to Nanjing in the days before China’s high-speed rail network simply to meet him and take an opportunity to study under Chris. That student went on to build a successful consulting career cleaning up contaminated groundwater sites in Shenzhen. “They have a lot of cleaning up to do in China,” Eastoe says.

Both Chris and his partner James have enjoyed the last year in Deloraine. They walk with the Deloraine Walking Club on expeditions into the Western Tiers, attend a small French conversation group at the Empire Hotel on Tuesday afternoons and have found, to their considerable surprise, a Quaker meeting that gathers in Deloraine on Sunday mornings. 

In the garden, Eastoe is relearning temperate horticulture after decades in the Sonoran Desert. Raspberry canes and fruit trees are going in. Old plantings keep surfacing through the grass at the back of the property, volunteers from whatever grew there before. He is happy to work around them.

“Deloraine’s a delightful town,” he says. “But I just love driving out through Meander to go hiking in the Western Tiers.”