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Student's
Report:
Greetings once
again from NOAA Ship Ronald H. Brown. This is Darin and Vito. We have
switched from the bridge so that we can work with the PMEL oceanographers.
We want to fill you in on what we have been doing.
The weather has been exceptionally
good for us the last two days. The water surface has been smooth with
slow moving swells that quietly pick up the ship and set her down. This
rocking motion is hard to describe but it makes you sleep well and reluctant
to get up in the morning. Today we are a little tired because we stayed
up so late watching the marine life in the lights on the "fan tail" (back
of the ship). We were visited by a large blue shark that loomed up from
out of the darkness. It appeared as the CTD was being lowered for another
tow-yo.
The crew has been relentlessly
pulling the rosette of sampling bottles and instruments up and down, into
and out of the hydrothermal vent plume along the South Cleft Section of
the ridge now for days. Mile after mile, the stainless steel reinforced
carrying device (rosette) has performed diligently. The ship has a pretty
good "eye" on the bottom but sometimes there are benthic features that
suddenly appear and it's too late to get the CTD out of harms way. That's
what happened yesterday but it's like Operations Officer LT Boland taught
us, it's good to have a back-up plan. They quickly replaced the old rosette
that was badly bent with a second one and transferred the bottles and
instruments to it.
The crew has resumed the
tow-yos and we are working with Dr. Baker in the lab. We have been plotting
points on a bathymetric chart (bottom contour chart) of the Axial Volcano
area. If you remember that a few days ago, we were tow-yoing and vertical
casting all around the Axial Volcano. Each time a water sample was taken,
Dr. Baker marked a point on the chart where the samples were taken. Currently,
we are plotting the latitude and longitude of each of those locations.
We note the Niskin sample bottle number that was closed at each of those
points on the computer and submit to Dr. Baker a printout of our findings.
Bathymetric charts can be used in navigation like surface charts. If you
ever loose your way at sea because your navigation system failed, bottom
contour charts can get you home. They show underwater features in great
detail depending on the scale. These charts have a contour interval of
5 meters and are very detailed. They are colored to enhance sudden rises
in benthic features so you can look at them to get a better understanding
of characteristics on the sea floor. Drawing lines on a chart that connects
points of equal depth makes bottom contour charts. It's kind of like when
you made "connect the dot" pictures in workbooks that you may have done
in elementary school.
Points of depth are determined
with an echo sounder. This is where a beam of sound is projected straight
down to the bottom through a transducer. After the sound wave hits the
bottom, it bounces back up to a receiver in the hull. Since we know how
fast sound travels through the water, all we need to know is how long
it takes to go and come back to the ship. That information is then calculated
to give us depth. The echo sounder on the Brown is louder as you get closer
to the bottom of the ship. It is always on and sounds like a bird chirping.
We were embarrassed earlier in the cruise when they first turned on the
echo sounder. We looked around the ladder wells and rooms for a bird that
we thought may have accidentally flown in while we were berthed in Victoria.
The captain toyed with us a bit but soon explained what it was.
Tomorrow is my (Darin)
birthday and I am looking forward to it. Our Chief Steward, Lito says
if we have calm weather, maybe we'll barbecue some of those squid we caught
last night. I hope so but we'll have plenty of burgers and hotdogs as
well. We will probably have to scrub extra dishes and make more work for
our selves but it will be fun. Students at sea may take a break for a
day or two because we are all writing an assignment from our senior English
teacher. We are writing short stories about a fictional person that goes
to sea for the first time on an oceanographic research vessel. This is
taking a while but the plot is pretty easy to imagine. Until then, we
wish you well and hope that your running lights burn bright.
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