Download PPT

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
 Challenger
expedition (1872-1876) -1st
systematic bathymetric survey
– ocean floor NOT flat - significant topographic
relief
ship Meteor (1920’s) - 1st
echosounding survey
 German
– sounds travels through water much better
– velocity = distance/time
– SONAR (Sound Navigation and Ranging)
Bathymetry - 2
 WWII
- U.S. Navy further developed SONAR
technology
– knowledge of the enemy
– knowledge of the ocean
 1950’s
- 1960’s - single, focused highfrequency, short wavelength sound beam
– “wide-beam” bathymetry
– sound beam spreads out as it reaches bottom
– range of depths - fuzzy estimate
single, focused high-frequency,
short wavelength sound beam
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
multiple, focused, high-frequency,
short wavelength sound beams
A Gigabyte of
data a day
A Gigabyte of
data an hour
multiple, focused, high-frequency,
short wavelength sound beams
Multibeam
Movies courtesy of NOAA
Bottom Coverage & Data Density by Survey Method
Leadline
1-2 K
soundings
per survey
Single Beam
500 - 750 K
soundings
per survey
Multibeam
400,000 – 1,000,000 K
soundings
per survey
Image courtesy of NOAA & UNH
Shallow Water Multibeam
Shallow Water Multibeam (cont.)
Initial Tutuila Surveys
Tutuila Surveys
Fagatele Bay National Marine Sanctuary
FBNMS Benthic Terrain
Entire Eastern Samoa
Need for Mapping Oregon Territorial Seafloor
Siletz Bay
Goldfinger et al., OSU Active Tectonics & Seafloor Mapping Lab
Oregon Department of Fish & Wildlife
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
“Fine Scale” Mapping
 on
the order of tens of meters to meters
 features the size of a can of beer!
Study Area
Image courtesy of Dan Fornari, Woods Hole Oceanographic Institution
HURL Sub &
ROV
surveys
Ka‘imikai-o-Kanaloa
Pisces IV or V
HURL = Hawaii Undersea Research Lab
ROV= remotely-operated vehicle
RCV-150
*Launch iTunesU
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
Sidescan Sonar
Image courtesy of USGS Woods Hole
DSL-120 Vehicle
Image courtesy of WHOI Deep Submergence Lab
and Dr.Dan Fornari
Image courtesy of USGS Woods Hole
Sidescan Sonar
Sidescan
Movies courtesy of NOAA
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
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 sedimentladen water
– deepsea fans
 continental
rise
 abyssal plain - extensive, flat
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
USS San Francisco crashed into
2-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
Seafloor Features: Deep Ocean
 Plate
Boundaries
– Ridges (Rises), Trenches, Transform Faults,
Fracture Zones