March 28, 2000
By Dr. Dan Fornari
Peter Lean, one of the students on board was watching the
eastern sky when he saw several small waterspouts. A waterspout
is a small tornado -- a whirling storm caused by winds. It
forms a funnel-shaped column of clouds that extends from
a dark black cloud in the sky right down to the sea surface.
Typically, the cloud column is 100 to 200 meters wide. Inside
the column, air moves upward and sucks up water from the
ocean surface. Waterspouts are common in tropical seas. This
morning, we saw three of them. They looked as if they were
pinning the cloud layer down to the ocean surface. These
are spectacular ocean events to witness--as long as they
are not big and are far away from the ship!
RV Melville continues
to steam slowly across a calm, clear blue sea at 1.4 knots.
Most people can walk faster than this speed. We travel so
slowly because -- 2,500 meters below us -- we are towing
the sonar fish only 100 meters above the seafloor.
If we go too fast, we would not have time to pull up or let
out some cable to fly the sonar fish over the
seafloors changing terrain. In addition, if the fish
flies too quickly over the seascape, it wont be able
to send and receive lots of sonar pings from
each parcel of ocean floor, which we need to make the clearest
possible images of the seafloor. It would be like trying
to see the landscape driving at 100 miles per hour.
If you were
a big, beautiful blue-and-yellow Mahi Mahi fish (also known
as a dolphin fish) watching the sonar fish,
or if you were aboard the Melville today, you might
not think we were doing much. But life is actually quite
hectic for scientists. Watches change every four hours, and
people are busy doing many different things to ensure that
we keep smoothly collecting our essential seafloor data.
We are about halfway done with our surveying here at the East Pacific Rise between
the latitudes of 9°N and 10°N. We plan to keep surveying here until Thursday
morning at about 0700 hours, and then pull the DSL-120 sonar up and head south
to our next survey site. We are using the computers on board to process the sonar
data and tomorrow we plan to lay out the records we have collected so far on
the floor of the Main Lab. That will give everyone a chance to think about what
the sonar images show and try to figure out where the eruptions have taken place
on the mid-ocean crest. This is the fun part of solving a science puzzle. After
the long wait between having an idea, writing and getting a research proposal
funded, and actually going out to sea, this makes all that waiting worth it!