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

Need for Mapping Oregon Territorial Seafloor

Siletz Bay

Applications for MappingApplications for Mapping

Tsunami Runup Models -Evacuation Planning

Habitat Restoration

Shoreline Change AnalysisAnalyzing 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.pdfdusk.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 AreaStudy 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