Labs Start Next WeekDon’t forget your lab book!!!
Read through labs ahead of time Exploring the Deep: GEO/OC 103 Lab
Manual by Hall-Wallace et al. TA assignments now updated on web
– dusk.geo.orst.edu/oceans/103labs.html
Shape of the SeafloorChapter 2
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)
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
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 A Gigabyte of data a data a dayday
A Gigabyte of A Gigabyte of data an data an hourhour
Bottom Coverage & Data Density by Survey MethodLeadline Single Beam Multibeam
1-2 K soundingsper survey
500 - 750 K soundingsper survey
400,000 – 1,000,000 K soundingsper survey
Image courtesy of NOAA & UNH
Shallow Water Multibeam
Shallow Water Multibeam (cont.)
Tutuila Surveys
Tutuila Surveys
Fagatele Bay National Marine Sanctuary
FBNMS Benthic Habitat
Goldfinger et al., OSU Active Tectonics & Seafloor Mapping LabOregon Department of Fish & Wildlife
Need for Mapping Oregon Territorial Seafloor
Siletz Bay
Applications for Mapping
Tsunami Runup Models -Evacuation Planning Habitat Restoration
Shoreline Change Analysis Analyzing Storm Impacts -Coastal Erosion
Fisheries ManagementCommercial 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
dusk.geo.orst.edu/3mile/consensus_statement.pdf
“Fine Scale” Mapping
on the order of tens of meters to meters features the size of a can of beer!
Image courtesy of Dan Fornari, Woods Hole Oceanographic Institution
Study Area
2005 HURL Sub & ROV surveys
Ka‘imikai-o-Kanaloa Pisces IV or V
RCV-150
HURL = Hawaii Undersea Research LabROV= remotely-operated vehicle
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 USGS Woods Hole
Image courtesy of WHOI Deep Submergence Laband Dr.Dan Fornari
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 sediment-laden 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
Seafloor Features: Deep Ocean Plate Boundaries
– Ridges (Rises), Trenches, Transform Faults, Fracture Zones
