Reading Material River Deltas from The Coast of Puget Sound J P Downing Puget Sound Books Field Trip B Working cruise in Puget Sound on the Thompson UW s oceanographic research vessel Wednesday October 24 All day no class Puget Sound Cruise Time Depart UW 7AM Oceanography Parking Lot Return UW 9 PM Oceanography Parking Lot Clothing foul weather gear hat fleece good shoes Prepare for cold wet windy and muddy conditions Food Lunch and dinner onboard ship Special dietary needs Observations during cruise Water column CTD chlorinity temperature depth turbidity suspended sediment Seabed Grab samples surface sediment box core 50 cm long piece of seafloor kasten core 250 cm long record of sedimentation Seafloor mapping multibeam acoustic profiles Below seafloor seismic profiles Puget Sound Morphology Glacial Origin scour flow under ice sheet formed depressions e g Main Basin Hood Canal Lake Washington sedimentary deposits also raised land surface glacial tills outwash deposits lake deposits old glacial sediment now provides new input to PS cliff erosion landslides land surface erosion Bathymetry water depth Shallow entrance glacial origin moraine oceanographic name sill primary sill is Admiralty Inlet Several others divide PS into separate basins 200 m Main Basin has 46 of water volume Sinuous shape result of origin Southern Basin has 29 of shorelines Fluvial river sediment supply fills PS from shoreline Whidbey Basin has 43 of tidelands Hydrography water properties Salinity amount of salt dissolved in water river water has 0 ppt parts per thousand ocean water has 35 ppt differs around world brackish water at depth in PS 20 30 ppt Density low salinity low density river plume flows over more dense brackish water Input of river water varies with space and time northern PS rivers supply the most water small input during late summer large input during late autumn and winter rains large input during spring snowmelt Types of river mouth environments estuary semi enclosed setting river and salt water meet and mix fjord estuary with glacial origin deep with shallow sill near mouth delta river mouth receiving much sediment estuary filled with sediment shoreline growing seaward Puget Sound Sedimentation Sources of sediment shallow shoreline erosion landslides deep biological productivity algal debris much carbon decomposes forming methane gas all depths river discharge deltas form near river mouths river plume carries sediment deeper near sill inflow with deep ocean water Mechanisms associated with Sedimentation plume transport turbid surface water river momentum tides wind flocculation silt and clay particles form larger aggregates which sink quickly landward bottom flow traps sediment near river delta formation thick deposits near river mouth topset tidelands foreset steep surface rapid accumulation bottomset deep deposits escape seaward Duwamish delta Intensely impacted by humans Wetlands hardened landfill roads parking lots buildings Distributary channels altered and stabilized depth in m Duwamish delta 4 m resolution 5x VE Nisqually delta nearly natural condition Several distributary channels bring water and sediment across delta to Puget Sound depth in meters Nisqually Delta 5x VE 3 m resolution looking SW heave squat pitch yaw tide position roll water column sound speed
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