Using sonar to create seafloor images
Updates: March 2000
|Daily Updates: May 2000
Latitude: 3 deg 7.8N
Longitude: 102 deg 12.7W
Wind Direction: NE
Wind Speed: 8 Knots
Sea State: 0
Height: 3-5 Foot
Sea Temperature: 84°F (28.9°C)
Barometric Pressure: 1012 MB
Visibility: 10-25 Nautical Miles
Corned beef hash and poached eggs
Creamed chip beef
Cottage potatoes and toast
Bacon and sausages
Hot and dry cereal
Assorted tropical fruits
Stuffed pork chops
Mashed potatoes with gravy
Pepper pot soup
Cheese and Salami tray
Homemade peanut brittle
King crab legs
Rice and zucchini
Banana cream parfait
Last night, Dave Grimes and Dave Murline
caught some enormous squid. They were bigger than the ones you
usually see either in aquariums or on your dinner plate when you
have calamari, the Italian name for squid. These squid will show up on our
dinner plates in the next few days as delicious entrees.
One benefit of being out at sea is getting fresh seafood almost any time.
The Daves are keeping us well stocked!
April 2, 2000
By Dr. Dan Fornari
The sun rose hot and bright this morning over a sparkling
blue sea. It was another beautiful day in the tropics, but you couldnt
tell if you were on duty inside the Control Van and paying close attention
to operating and monitoring the DSL-120 sonar fish. The windowless van is
usually kept dark so that people can see the TV and computer monitors better.
After a four-hour watch, you walk outside and feel what a mole must feel
like coming out of its hole-dazed and shocked at how bright the sun is.
We are continuing to tow the DSL-120 sonar fish north and
south along the crest of the East Pacific Rise near 3° 20N latitude.
We are flying the fish over a zone where the AHA hydrophones indicated that
earthquakes occurred four years ago. We are searching for evidence of that
seafloor volcanic eruptions took place here. We are also busy making maps
of the seafloor and we will post a few of them on the Web in the coming
days to give you a picture of what the seafloor looks like where we are
working. We dont have maps right away because we are not taking photos
of the seafloor. We are bouncing sound waves off the seafloor and then processing this
data to make an image. In a way, we are translating sound into a picture.
Many techniques are used to process the many different types of data we
collect, and many people on board specialize in this work. Uta Peckman of
Scripps specializes in processing multibeam sonar data. Steve Gegg is the
expert data processor of the Woods Hole Deep Submergence Operations Group
on board. Tom Crook, also part of the Woods Hole team, is the expert navigation
data processor. Rob Palomares of Scripps is the expert processor of CTD
data (conductivity, temperature and depths of water). Dan Scheirer, Paul
Johnson, Gregg Kurras, Julia Getsiv and Scott White are all scientists working
on processing the different data we are collecting during this expedition.
Over the past week, we have sent back a lot of information about what we are
doing on board RV Melville. The students on board and I thought it might
be fun for you to try a Sea Quiz that we put together.
|Dive and Discover
Sea Quiz #1
The East Pacific Rise is:
a) the name of a mountain range in South America.
b) located in the North Atlantic Ocean.
c) a mid-ocean ridge spreading center in the eastern Pacific Ocean.
d) a transform fault.
A multibeam sonar is:
a) a navigation device that gives latitude and longitude of a ship.
b) a sonar that emits a single ping of sound to determine seafloor depth.
c) an instrument to listen to music.
d) a sonar mounted on the hull of a research ship that emits many pings
of sound to produce data to make seafloor maps.
The mid-ocean ridge is:
a) a plate boundary where Earths ocean crust is formed.
b) a mountain range in Asia.
c) a line of volcanoes in the middle of a plate, like the Hawaiian Islands.
d) a transform fault.
Global Positioning System (GPS) navigation uses:
a) transponders to determine latitude and longitude.
b) several satellites that help determine the accurate geographic
location of ships, planes, cars and people on Earths surface.
c) telephones to communicate between ships at sea.
d) sound waves to determine seafloor depths.
[Click here to see your answers].