25 deg 19S
Longitude: 70 deg 02E
Wind Direction: NW
Wind Speed: 12 Knots
Sea State 2
Swell(s) Height: 3 Foot
Sea Temperature: 79°F (26.1°C)
Barometric Pressure: 1011.3 MB
Visibility: 18+ Nautical Miles
Daily Update: Ocean Floor Mapping
By Amy Nevala
Susan Humphris and Dan Fornari spent last night making maps.
Not just any maps, but special topographic maps of a portion
of the Central Indian Ridge.
people visit a new place on land, they use a map. The same
is true in the ocean. Oceanographers map the seafloor to
measure its depth and learn about the topography, or mountains,
valleys and other physical features.
maps we create guide us to interesting spots for studying hydrothermal
vents in the Indian Ocean.
using the different types of sonar systems on Knorr, we
can make maps of the seafloor that cover both large and small
areas. One of these systems, called the multibeam sonar, is mounted
across Knorrs hull and allows us to map areas covering
hundreds of square miles.
Another type of multibeam sonar, the SM2000, is mounted
on ROV Jason. It creates detailed maps of individual vent chimneys,
which help scientists to locate biological, chemical and geological
The multibeam bathymetric maps we made earlier give us a birds eye
view of the seafloor, said Dan. The SM2000 maps we made last night
give us the gnats eye view.
Bathymetric maps show depth and give us a sense of
the orientation and shape of the seafloor. The maps outline features
like the mid-ocean ridge, which rises like a mountain range.
When using multibeam sonar, the ship steams along
a series of specific latitude and longitude points. Then Knorrs sonar system sends sound to the seafloor,
which bounces back to the ship as a depth signal. Our computers use this depth
data to create the rainbow-colored bathymetric maps, with reds representing the
higher peaks and blues the lower valleys.
Many people on board Knorr help Dan and Susan
make the maps. Paul Johnson, Cindy Sellers, Amy Simoneau and Dave
Sims are creating maps of our study area at different scales. Their
work will be useful in the days ahead as we reconstruct our observations
and sampling activities at this hydrothermal vent site.
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