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GEO/OC 103 Exploring the Deep …. Today’s Tune “ Sink to the Bottom” Fountains of Wayne

GEO/OC 103 Exploring the Deep …. Today’s Tune “ Sink to the Bottom” Fountains of Wayne. Labs Start Next Week. Read through labs ahead of time See your sections and TAs on the web dusk.geo.orst.edu/oceans/103labs.html. Shape of the Seafloor. Techniques of Bathymetry - 1.

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GEO/OC 103 Exploring the Deep …. Today’s Tune “ Sink to the Bottom” Fountains of Wayne

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  1. GEO/OC 103Exploring the Deep ….Today’s Tune“Sink to the Bottom”Fountains of Wayne

  2. Labs Start Next Week • Read through labs ahead of time • See your sections and TAs on the web • dusk.geo.orst.edu/oceans/103labs.html

  3. Shape of the Seafloor

  4. Techniques of Bathymetry - 1 • Challenger expedition (1872-1876) -1st systematic bathymetric survey • ocean floor NOT flat - significant topographic relief • German ship Meteor (1920’s) - 1st echosounding survey • sounds travels through water much better • velocity = distance/time • SONAR (Sound Navigation and Ranging)

  5. Bathymetry - 2 • WWII - U.S. Navy further developed SONAR technology • knowledge of the enemy • knowledge of the ocean • 1950’s - 1960’s - single, focused high-frequency, short wavelength sound beam • “wide-beam” bathymetry • sound beam spreads out as it reaches bottom • range of depths - fuzzy estimate

  6. single, focused high-frequency, short wavelength sound beam

  7. Bathymetry - 3 • 1970’s - revolution in bathymetric mapping with multibeam bathymetry • multiple, focused, high-frequency, short wavelength sound beams • “narrow-beam” or “multibeam” bathymetry • sound beam stays narrow and focused all the way to the bottom • depths much more precise • e.g., Sea Beam has 16 beams, Sea Beam 2000 has 121, Simrad EM120 has 191

  8. multiple, focused, high-frequency, short wavelength sound beams A Gigabyte of data an hour A Gigabyte of data a day

  9. multiple, focused, high-frequency, short wavelength sound beams Multibeam Movies courtesy of NOAA

  10. Bottom Coverage & Data Density by Survey Method Leadline Single Beam Multibeam 1-2 K soundings per survey 500 - 750 K soundings per survey 400,000 – 1,000,000 K soundings per survey Image courtesy of NOAA & UNH

  11. N

  12. N

  13. Shallow Water Multibeam

  14. Shallow Water Multibeam (cont.)

  15. Initial Tutuila Surveys

  16. Tutuila Surveys

  17. Fagatele Bay National Marine Sanctuary

  18. FBNMS Benthic Terrain

  19. Entire Eastern Samoa

  20. Need for Mapping Oregon Territorial Seafloor Siletz Bay Goldfinger et al., OSU Active Tectonics & Seafloor Mapping Lab Oregon Department of Fish & Wildlife

  21. Applications for Mapping

  22. “Fine Scale” Mapping • on the order of tens of meters to meters • features the size of a can of beer!

  23. Study Area Image courtesy of Dan Fornari, Woods Hole Oceanographic Institution

  24. HURL Sub & ROV surveys *Launch iTunesU Ka‘imikai-o-Kanaloa Pisces IV or V HURL = Hawaii Undersea Research Lab ROV= remotely-operated vehicle RCV-150

  25. Sonar Also Used as... • a “catscan” of oceans to see water structure ABOVE seafloor • an “x-ray” of seafloor to see structure BENEATH seafloor • seismic reflection & seismic refraction • low frequency, long-wavelength sound • sidescan sonar to get pictures of seafloor in addition to depth • backscatter strength as opposed to traveltime

  26. Sidescan Sonar Image courtesy of USGS Woods Hole

  27. DSL-120 Vehicle Image courtesy of WHOI Deep Submergence Lab and Dr.Dan Fornari Image courtesy of USGS Woods Hole

  28. Sidescan Sonar Sidescan Movies courtesy of NOAA

  29. Resolution • with multibeam bathymetry can see things on seafloor the size of this room • swath width of 6 km or 3.7 miles • good, high-resolution maps possible only since 1980’s • other instruments needed to see things smaller than size of room • remotely-operated vehicles (ROVs) • submersibles

  30. Seafloor Features: Continental Margins • continental shelf - extends from shore to a point marked by great increase in slope • continental slope - steep slope beyond the continental shelf break • slopes often cut by submarine canyons • turbidity currents - dense flows of sediment-laden water • deepsea fans • continental rise • abyssal plain - extensive, flat

  31. Seafloor Features: Deep Ocean • seamounts - underwater volcanoes 500 m to 1000 m high • flat-topped ones are called guyots • volcanic features (buoyed up by hot rock, lava) • abyssal hills - features around 200 m high • pervasive on seafloor • volcanic AND tectonic in origin - still debated

  32. USS San Francisco crashed into2-km tall uncharted seamount • Los Angeles class nuclear submarine ran aground enroute from Guam to Brisbane, Australia - 8 January, 2005 • One sailor killed, 115 injured • 30-hour trip back to Guam, crew managed to keep the sub from sinking Courtesy of Dave Sandwell, Scripps Institution of Oceanography

  33. Seafloor Features: Deep Ocean • Plate Boundaries • Ridges (Rises), Trenches, Transform Faults, Fracture Zones

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