EXPLORING THE EVOLUTION OF CHESAPEAKE BAY OVER THE LAST TWO GLACIAL CYCLES USING 3D VISUALIZATION AND ANIMATION

A project of 3D visualization and animation was undertaken in an attempt to better understand the recent geomorphic evolution of the Chesapeake Bay region. The process of developing a continuous sequence of seamless bathymetric-topographic surfaces over multiple rises and falls of sea level made it necessary to synthesize a variety of datasets in unique ways. Existing geospatial data incorporated into the animation included: (1) maps of Pleistocene erosional surfaces beneath the bay prepared from seismic survey data, (2) modern bay bathymetry from the NOAA-NOS Chesapeake Bay, VA/MD (M130) Bathymetric Digital Elevation Model (~30-m resolution; 1998), (3) modern inner continental shelf bathymetry from the NOAA-NGDC Coastal Relief Model Vol. 02 (~90-meter resolution; 1999), and 4) topography from the USGS National Elevation Dataset (~30-m resolution; 2007). Radiocarbon and uranium series ages, combined with optically stimulated luminescence (OSL) ages from various formations on the southern Delmarva Peninsula were used for timing and relative sea-level control. ArcGIS software was used for map registration, digitizing, and surface generation using 500-m grid cells. Surfaces were combined using EarthVision software to verify and visually check the horizontal and vertical compatibility of the merged datasets in a 3D model. Morphing of surfaces was primarily performed using ImageMagick software; Adobe Flash software was used to build the final animation by combining the generated topo-bathy surfaces with semi-transparent ocean, river, and land overlays. The animation shows 200,000 years of bay history in 1,200 frames, at a rate of 12 frames per second. Geomorphic processes shown by the animation include incision and deflection to the south over time of the paleo-Susquehanna valley and progressive capture of western shore rivers during lowstands, as well as pulsed progradation of the Delmarva spit during successive sea-level highstands, resulting in partial infilling of incised paleochannels (Cape Charles, Eastville, etc.) and narrowing of the bay mouth. Challenges encountered in constructing the animation included creation of geologically reasonable transitional sequences, and depiction of intervals where disagreement exists about the position of relative sea level in the region (e.g., MIS 3).