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          Front Page

Curiosity's Light Led to Finding

By John Fleck
Journal Staff Writer
    SOCORRO— Fred Phillips was 15 when he looked up into the Sierra Nevada and asked his geology teacher what seemed like a simple question.
    Above them in the California mountains were distinctive piles of earth and rock.
    Piled up as glaciers pushed downhill like bulldozers, the rocks were left when the glaciers retreated. Geologists call them "moraines," and they were a ubiquitous feature in the California mountains of Phillips' youth.
    "I remember asking the instructor of the class, 'How old are those moraines up there?' '' Phillips recalled. "He told me 'Nobody knows.' ''
    Phillips was a curious kid. Now 52 and a professor at the New Mexico Institute of Mining and Technology, he has built an internationally renowned career on the search for an answer.
Seeds of curiosity
    West of Mono Lake in California's Owens Valley, Bloody Canyon slices through a classic moraine as it drains the high Sierra Nevada.
    The rock pile's age— 18,000 years, give or take a bit— is one piece of a global puzzle assembled last month by Phillips and his colleagues in the journal Science.
    By dating the Bloody Canyon moraine and 10 like it around the world, the scientists determined that the end of the last ice age— the point in Earth history when the glaciers finally began retreating for good— happened roughly simultaneously around the world.
    The story of how the scientists got to that point is a testament to the power of the curiosity aroused in a teenage Fred Phillips by that long-ago conversation with his first geology teacher.
    As a scientist, Phillips is hard to pigeonhole. His academic title is "professor of hydrology" at New Mexico Tech, and understanding ground water occupies a big part of his scientific life.
    One of the things ground water scientists struggle to understand is how long the water has been down there, and that's what Phillips was focused on when he had his "aha" moment.
    The scientists were using a type of chlorine as a tracer to date the water's age when Phillips ran across a paper by a scientist arguing that, over time, the same type of chlorine would build up on a rock lying on the surface of the Earth.
    Cosmic rays banging in from outer space create the chlorine. The longer the rock has been lying in the open, the more chlorine there would be.
    Phillips remembered the question that had nagged at him when he was 15.
    "I read this paper, and this light went on in my head," Phillips said.
    Phillips' application for a research grant was turned down, but he cobbled together a tiny effort anyway. It led to a groundbreaking paper in January 1986 in Science.
    "Looking back at it now," Phillips said in a recent interview about that first work, "it was all incredibly crude and haphazard, but you've got to start somewhere."
    Phillips, using chlorine as his clock, was the first to publish, but in short order three other scientific teams showed how to do the same thing using other elements, and a new scientific field was born.
A field opened wide
    The implications reach far beyond dating glacial moraines. Earthquake faults, ancient shorelines and newly uplifted mountains can all be dated using the techniques.
    To "hydrology," then, you can add the term "geomorphology"— the study of how landscapes form— to Phillips' list of academic qualifications. Last year, the Geological Society of America gave Phillips its Kirk M. Bryan award for his contributions.
    "Generations of geomorphologists have said, 'I'd give anything to know how old this is,' '' Phillips said. "Now we can do it."
    But like most good scientists, Phillips is not entirely satisfied with the results to date.
    Imagine that you've got a trophy on your mantle, and you're trying to figure out how long it's been sitting there based on the thickness of the layer of dust.
    To do that, you'd need to know how fast the dust is building up.
    That is the problem faced by Phillips and his colleagues in the cosmic ray-dating community. Using a variety of techniques, they've come up with increasingly accurate estimates of the "cosmic ray flux" over time. But there are still uncertainties.
    Cosmic ray flux can vary with latitude and altitude, and it has also likely varied over time.
    That is why Phillips is heading a $6 million National Science Foundation effort to improve the accuracy of the scientists' cosmic clock.
    Thirteen universities are involved, along with a European Union team.
    "This has tremendous implications for a whole number of disciplines," said Enriqueta Barrera, the NSF program director overseeing the project.