Geography and Oceanography - Chapter 3 pot

Navy further developed SONAR technology – knowledge of the enemy – knowledge of the ocean high-frequency, short wavelength sound beam – “wide-beam” bathymetry – sound beam spreads out as

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

German ship Meteor (1920’s) - 1st

Bathymetry - 2

WWII - U.S Navy further developed SONAR technology

– knowledge of the enemy

– knowledge of the ocean

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

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

multiple , focused, high-frequency,

short wavelength sound beams

Multibeam

Movies courtesy of NOAA

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

Shallow Water Multibeam

Shallow Water Multibeam (cont.)

Initial Tutuila Surveys

Tutuila Surveys

Fagatele Bay National Marine Sanctuary

FBNMS Benthic Terrain

Entire Eastern Samoa

Goldfinger et al., OSU Active Tectonics & Seafloor Mapping Lab

Oregon 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 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!

Image courtesy of Dan Fornari, Woods Hole Oceanographic Institution

Study Area

HURL Sub &

ROV surveys

Ka‘imikai-o-Kanaloa Pisces IV or V

RCV-150

HURL = Hawaii Undersea Research Lab

ROV= remotely-operated vehicle

*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

in addition to depth

– backscatter strength as opposed to traveltime

Sidescan Sonar

Image courtesy of USGS Woods Hole

Sidescan Sonar

Sidescan

Movies courtesy of NOAA

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

point marked by great increase in slope

continental shelf break

– turbidity currents - dense flows of

Seafloor Features: Deep Ocean

to 1000 m high

– flat-topped ones are called guyots

– volcanic features (buoyed up by hot rock, lava)

– 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

Seafloor Features: Deep Ocean

Plate Boundaries

– Ridges (Rises), Trenches, Transform Faults, Fracture Zones