Geography and Oceanography - Chapter 3 pot

GEO/OC 103
Exploring the Deep ….
Today’s Tune
“Sink to the Bottom”
Fountains of Wayne
Labs Start Next Week
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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
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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
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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
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1970’s - revolution in bathymetric mapping
with multibeam bathymetry
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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
day
day
A Gigabyte of
A Gigabyte of
data an
data an
hour
hour
multiple, focused, high-frequency,
short wavelength sound beams
Multibeam
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