Tom Pierson’s talk to GSOC focused on his study of the aggradation and erosion of volcanic sediment that occurred in the Rio Chaiten valley as a result of the December 2008 and February 2009 eruptions of the Chaiten volcano in the southern region of Chile. Pierson, who has worked at the USGS Cascades Volcano Observatory since 1981, has traveled the Pacific rim studying hydrologic and geomorphic responses to volcanic eruptions.