Introduction

These maps show the sea floor topography and backscatter intensity of the region offshore of Boston, Mass., at a scale of 1:125,000. Sheet 1 shows seafloor topography in shaded relief view, with sea floor depth superimposed in color. Sheet 2 shows sea floor topography in shaded relief view, with backscatter intensity superimposed in color. Both sheets also show smoothed topographic contours at selected intervals. The maps are based on multibeam echo-sounder data collected on four cruises conducted between the fall of 1994 and the fall of 1998. Additional sea floor bathymetry from the National Geophysical Data Center (NGDC) Coastal Relief Model and onshore topography from the U.S. Geological Survey (USGS) Digital Elevation Model (DEM) are also included. The maps combine multibeam echo-sounder data collected as part of the Stellwagen Bank National Marine Sanctuary map series (Valentine and others, 2001, 2003a–c) and the companion western Massachusetts Bay map series (Butman and others, 2003a–f). For a more detailed description of seabed features, see the maps at a scale of 1:25,000 for quadrangles 1-18 in the Stellwagen Bank National Marine Sanctuary map series, and quadrangles 1 and 2 in the western Massachusetts Bay map series.