AMHERST, Mass. – Geochemist Isaac Larsen at the University of Massachusetts Amherst has been granted a Fulbright U.S. Scholar award and will spend the coming spring semester at the University of Salzburg, Austria.
The U.S. Department of State and the J. William Fulbright Foreign Scholarship Board points out that the program, funded by Congress, awards recipients on the basis of academic and professional achievement, record of service and demonstrated leadership in their respective fields. Larsen is one of over 800 U.S. citizens who will teach, conduct research and/or provide expertise abroad for the 2019-2020 academic year in over 160 countries.
He will teach graduate courses and conduct research on Earth surface changes using cosmogenic nuclide geochemistry techniques to study erosion rates using sand samples from rivers and river terraces in non-glaciated Alpine landscapes, as well as investigating how they respond to climate change.
Cosmic rays – high energy particles originating in the cosmos – continually bombard the Earth and smash into oxygen atoms and produce a rare cosmogenic isotope called Beryllium 10 (10Be), Larsen explains. “It’s like a person sunbathing,” he says. “The longer you’re exposed, the more you’ll burn.” In the same way, in areas where erosion is rapid there will be shorter exposure and lower 10Be levels, but a grain of sand in an area that is eroding more slowly will have longer exposure and a higher concentration of 10Be. Comparing nuclide measurements in the different samples reveals the rate of erosion in each.
The geomorphologist says this research is planned for about 20 sites on the Bohemian Massif and the Alpine Foreland north of the Alps because there he can collect sand samples from river terraces that remain from the last ice age. “In non-glaciated areas there it was much colder than it is in the present day. It’s been proposed that erosion rates increased globally during the ice age, but that’s controversial,” he points out. “We’re going to try to understand how erosion rates respond to climate change by measuring modern rates and comparing that to samples in river terraces and rivers from those sites.”
Larsen will collaborate with colleagues at the University of Salzburg for these studies. He will bring the Alpine samples back to his UMass Amherst lab for analysis, which involves dissolving sand grains and separating the 10Be so it can be analyzed in an accelerator mass spectrometer that can measure individual atoms. The specialized equipment for this is available in only a few research facilities in the world.
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