The authors thank the captain and crew of the NOAA ship Thomas Jefferson for their work in collecting and processing bathymetry and sidescan-sonar data. We also thank Barry Irwin, the captain of the RV Rafael, for his support in collecting sediment samples and bottom photography. This report has benefited from critical reviews by Jason Chaytor, VeeAnn Cross, and Emily Himmelstoss (all of the USGS).