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Expedition
to the Mariana forearc
Mar.
23 - May 4, 2003
Day
33, April 24th
(click
on any image for the larger version)
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Day
33 BENTHIC TUMBLEWEEDS
Just
after midnight at Blue Moon Seamount, we brought up the piston core
with a beautiful, long sample of blue mud. I helped wash down the
deck and finally went to bed at 0230. The scientists were still
in the lab and the Jason Team continued working on the repair of
Jason’s tether.
We
were hoping for a 0800 launch of Jason. Rob,
one of the science technicians, set up the ship’s sonar to
map another segment of the sea floor that Patty
requested for the 6 hours between the piston core and Jason launch.
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| Jason
was back in the water by 0830 and started the long trek to the seafloor.
Our goal was to find the site of the recent piston core that we hoped
to be a recent serpentine mud eruption. That was the 25th core of
this trip and is referred to as PC-25. Within minutes of reaching
the bottom we came upon more man-made debris. Yesterday we found the
heat-flow outriggers—today we found a core catcher that holds
the mud in the plastic pipe liner as the core pipe is brought to the
surface. The core catcher is not very large but it was shiny and easy
to see on the bottom as something man-made. Two days in a row we have
landed on debris from our own studies, but two days in a row we have
not found the core sites we were looking for. Each core site had been
marked with a plastic bucket lid, but after 4 hours of searching we
went on to explore more of the summit of Blue Moon. |
Core
catcher on bottom
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| Eleven
hours of exploration over a muddy and frequently rocky bottom. I am
learning to distinguish between a bottom covered with sediments that
have fallen to the sea floor and a cover of serpentine mud that has
oozed up from the subducting plate. My night watch, 2000 to midnight
was just reaching an end when we came across an incredible formation
on the sea floor. It wasn’t tall but it was easily 8 feet in
diameter. The formation was circular and contained millions of what
appeared to be fluffy mud puff balls. We all just watching in awe
and as we watched we saw that, with the slightest current, the puff
balls would roll across the seafloor. None of us had ever seen anything
like them before. As we explored we found other circular clusters,
equally as large, of the same material. |
Benthic
tumbleweeds, setting push core in place to take sample.
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We
all had ideas about the source of the puff balls. Our ideas ranged
from eggs, to fecal pellets to something geological forming as fluids
made their way to the surface of the seafloor. We were all hoping
it was geological. Each of us was thinking we might have found the
deep sea version of bubbling mud pots. We took 2 samples using the
push cores, working slowly and carefully get some of the puff balls
in the core tube. Patty, the Chief Scientist, was due for the midnight
watch so we stayed in the area until she arrived. We were so excited.
When she arrived, we all started talking at once, but she took one
look at the video monitor and said, “Oh, it’s probably
just poop.”
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Sam
was also on the midnight watch and when he arrived he explained
the mystery. Animal wastes and byproducts can be mucus-like and
sticky. As the organic debris drifts along the seafloor it can pick
up sediment and mud. The currents tend to deposit the puff balls
in particular locations, usually areas with depressions. Sam had
seen this in Monterey Canyon off the coast of California where one
of his professors referred to them as benthic tumbleweeds.
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Benthic
tumbleweeds, taking sample with push core.
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Benthic
tumbleweeds, retrieving push core.
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Jason
is stuck in the water due to high seas. It is too dangerous to try
and get him back on the ship so we continue to explore the summit
of Blue Moon. Walking around on deck is a bit more difficult and
I recently said that the ship was rocking a lot. I was quickly informed
that ships to not rock. Ships can
1. Pitch: bow and stern go up and down, alternately.
2. Roll: move side to side.
3. Yaw: bow swings from port to starboard.
4. Heave: entire ship moves up and down.
5. Surge: entire ship moves forward and backward.
6. Sway: entire ship moves side to side.
But, a ship does not rock.
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Science
Summary - Day 33, April 24th
Science
Objecives, Day 33:
The
thirty-third day of the cruise, Apr. 24, as the ROV had to be recovered
early yesterday and we had to perform a piston core late in the
evening, we will do a bathymetric survey of Blue Moon Seamount from
midnight until 0800 in the morning. We will launch Jason2/Medea
at 0800 and explore a topographically upraised feature on the southwest
edge of the seamount summit. This appears as a dark backscatter
patch on the side scan image from our 1997 cruise and is possibly
a newer serpentine protrusion site. We will also explore the summit
fault trace on this seamount and look for signs of fluid emanations
(chimneys!).
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