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Expedition
to the Mariana forearc
Mar.
23 - May 4, 2003
Day
3, March 25
(click
on any image for the larger version)
By
Linda Tatreau
| Today
(beginning last night and continuing into the wee hours of the morning)
we attempted to take a core
sample from the summit of Deep Blue Seamount. I had heard about
the procedures involved in taking core samples and I was excited about
watching the process. I quickly learned that there is not much point
in getting excited as it takes hours to see the results. The gravity
coring system, preset with one section of pipe to take a 10-foot sample,
was put into position by the crane
and the winch was readied for the
drop. This took an hour. Then there was a 3-hour trip to the bottom.
|
Crane with the corer beneath |
The
core technician laughed that he was making his deepest drop to take
a core sample from the top of something. The summit of Deep Blue Seamount
is 6500 meters deep--almost 4 miles! We are so close to the Marina
Trench--the deepest place on Earth—you can’t tell from the surface
but you get a thrill just knowing it’s there. |
| Riding
above the core pipe was the 3,500 pound core weight. As the winch
let the apparatus sink to the sea floor, the cable wire added to the
weight. By the time the core pipe reached the bottom, the weight above
it was an amazing 12,000 pounds. |
The big winch! |
|
Twelve
thousand pounds—6 tons—to drive the core pipe into the sediments.
Then patience. It was a 4-hour trip back to the surface. The excitement
builds as the geologists will get their first look at the muds from
this seamount, the chemists will get to squeeze out the pore water
and look at the chemistry, and the microbiologist will get to look
at microbes from this extreme environment. I was really disappointed
when the core pipe came back empty. The scientists take their disappointment
as a learning experience and move forward with more knowledge and
even more questions.
The
next try at getting a core sample will have to wait for a couple
of days. The DSL-120 sonar is repaired so we head back to South
Chamorro Seamount to resume the mapping process.
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| Since
this ship operates on a 24-hour schedule, the days and nights blend
together into a continuous working schedule. The DSL-120 was deployed
at 0815 so we have only just begun Day 3. Three hours to the bottom
and another 4.5 hours to get on track and today’s first transect is
mapped by sonar. The navigator in the control van and the officer
on the bridge had a really difficult time turning the ship for the
next transect because of an incredibly strong surface current. |
The DSL 120 on the crane |
|
They
can’t just turn the ship; they must consider the drag from the fish
(DSL-120), keeping the fish off the bottom, the angle of the cable
to the ship, and the angle of the sheave.
The turn took over 5 hours and the mapping continued into the night.
Science
Summary - Day 3, March 25
By
Patricia Fryer
Science
Objectives, Day 3:
After the early morning deep core, which impacted too hard a surface
to recover any sediment, we transited back to South Chamorro Seamount
and deployed the DSL120 system to finish the survey of the new vent
area at the summit of the mud volcano. The deployment went perfectly
and the system started out returning good data. We plan to run track
lines over the summit mound and then we will transit to the next
mud volcano.
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