GEO/OC 103 Exploring the Deep

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GEO/OC 103Exploring the Deep .Todays
TuneSink to the BottomFountains of Wayne
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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

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Shape of the Seafloor
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Techniques of Bathymetry - 1

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

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Bathymetry - 2

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

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single, focused high-frequency, short wavelength
sound beam
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Bathymetry - 3

• 1970s - 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

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multiple, focused, high-frequency, short
wavelength sound beams
A Gigabyte of data an hour
A Gigabyte of data a day
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multiple, focused, high-frequency, short
wavelength sound beams
Multibeam
Movies courtesy of NOAA
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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
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Shallow Water Multibeam
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Shallow Water Multibeam (cont.)
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Initial Tutuila Surveys
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Tutuila Surveys
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Fagatele Bay National Marine Sanctuary
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FBNMS Benthic Terrain
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Entire Eastern Samoa
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Need for Mapping Oregon Territorial
Seafloor Siletz Bay
Goldfinger et al., OSU Active Tectonics
Seafloor Mapping Lab Oregon Department of Fish
Wildlife
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Applications for Mapping
Tsunami Runup Models -Evacuation Planning Habitat Restoration
Shoreline Change Analysis Analyzing Storm Impacts -Coastal Erosion
Fisheries Management Commercial Fishing Marine Reserve Design
Emergency Response, Impact Assessment Port Security
Maps and Visualizations Navigation Products, Services
Wave Energy Oil Spill Response, Tracking
Coastal tourism, recreation MANY others
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Fine Scale Mapping

• on the order of tens of meters to meters
• features the size of a can of beer!

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Study Area
Image courtesy of Dan Fornari, Woods Hole
Oceanographic Institution
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HURL Sub ROV surveys
Launch iTunesU
Kaimikai-o-Kanaloa
Pisces IV or V
HURL Hawaii Undersea Research Lab ROV
remotely-operated vehicle
RCV-150
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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

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Sidescan Sonar
Image courtesy of USGS Woods Hole
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DSL-120 Vehicle
Image courtesy of WHOI Deep Submergence Lab and
Dr.Dan Fornari
Image courtesy of USGS Woods Hole
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Sidescan Sonar
Sidescan
Movies courtesy of NOAA
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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
  1980s
• other instruments needed to see things smaller
  than size of room
• remotely-operated vehicles (ROVs)
• submersibles

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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

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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

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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
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Seafloor Features Deep Ocean

• Plate Boundaries
• Ridges (Rises), Trenches, Transform Faults,
  Fracture Zones