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48°30'
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Arc Explorer
Themes visible in the above map: LATITUDE/LONGITUDE and RELIEF(Image). There are four themes which make up the bathymetry data: BATHYMETRY (Image) theme which is a color image of the bathymetry, the BATHBAR (Image) theme which provides a legend for the BATHYMETRY (Image) theme, the RELIEF (Image) theme is a gray-scale image which incorporates the topography and bathymetry and the BATHYMETRIC CONTOURS vector data theme. Only data from the BATHYMETRIC CONTOURS theme can be queried as the other two themes are images. The CONTOURS field contains the depth value for each contour line. Please note that the depths are given as negative values (depth below sea level) in the Arc Explorer data.

Modern surface morphology of the eastern Juan de Fuca Strait
David C. Mosher, Robert Kung and Antony T. Hewitt

The bathymetric/relief map represents a compilation of historic hydrographic field sheet data and multibeam bathymetric data. The field sheet data are derived from single beam echosounding by the Canadian Hydrographic Service (CHS) and the National Oceanographic and Atmospheric Administration (NOAA) of the U.S. The NOAA field sheet data are available digitally through the National Geophysical Data Center . The CHS field sheet data are available digitally from Nautical Data International. Multibeam bathymetric data were collected from the Victoria waterfront during cruise PGC98004 and subsequent surveys by the CHS and the Acoustic Data Analysis Centre - Pacific of the Department of National Defense.

The overall shape of the Strait is bedrock controlled, enhanced by glacial deposition and scouring during numerous Pleistocene glaciations. Water depths range to 250 m in the study region. The present-day seafloor relief is quite variable as a result of the many shallow banks and intervening deep troughs. These features may result from glacial deposition and erosion during the Pleistocene, or may, in part, be tectonically controlled. The banks are glacial drumlins, and side- and end-moraines (Figure 1). The upper surfaces of some of the shallower banks have been eroded during lower relative sea level stands. A set of "braided" channels is apparent, emanating from Puget Sound at Admiralty Inlet, likely resulting from outwash during melting of the Puget Lobe glacier, but perhaps tectonically controlled as well. Draping of the topography is obvious to the east and west of Whidbey Island, resulting from reworking (erosion and redeposition) of abundant Pleistocene sediment comprising much of Whidbey Island and surrounding land-mass.

Multibeam sonar data are available only along the Victoria waterfront (Figures 2-8) and off of Race Rocks. These data provide a scale of resolution impossible to achieve by conventional sounding techniques and show many features, anthropogenic and natural, that otherwise would not be observed. These data, combined with limited sidescan sonar data, indicate that it is likely much of the seafloor is covered by bedforms, resulting from reworking of material by strong tidal and estuarine circulation currents within the strait. The largest of these bedforms is a set of massive sand dunes just east of Victoria (Figure 3), in which dune height is up to 25 m. Paleoshorelines are also obvious on the multibeam data (Figure 4) as are pipelines, cables, and other sources of debris.

 

Reference citation:

Mosher, D.C., Kung, R., and Hewitt, A.T., 2000. Modern surface morphology of the eastern Juan de Fuca Strait, in: Mosher, D.C. and Johnson, S.Y. (Eds.), Rathwell, G.J., Kung, R.B., and Rhea, S.B. (Compilers), Neotectonics of the eastern Juan de Fuca Strait; a digital geological and geophysical atlas. Geological Survey of Canada Open File Report 3931

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Moraines Sandwaves Race Rocks Victoria Waterfront