Travel Reference
In-Depth Information
which often can be used like a fingerprint to identify an individual species,
get more and more complex through time? The answers to this particulat
problem came from an engineer.
Understanding ammonites, perhaps the most common and iconic of all
Mesozoic invertebrates, really starts by studying submarines. And a horrible
marine accident that happened nearly 30 years ago focused much attention
on how ammonites may—or may not—have used their complex septa (the
walls that divide the shell into chambers).
On April 10, 1963, the United States nuclear submarine
Thresher
ex-
ceeded a still-classified depth and imploded, killing its 146 crew members in
the process. Its remains sank to the bottom of the Atlantic Ocean, at a depth
of 8500 feet about 100 miles east of Cape Cod. They rest there still, along
with the remains of the crew, scattered over 400 square yards of muddy bot-
tom. The United States Navy, using remote submersibles, visits this sad
grave regularly to monitor the fate of the poisonous plutonium and other ra-
dioactive waste now buried at this site. Four or five larger pieces can be ob-
served: The sail, sonar dome, bow section, tail, and engineering sections are
recognizable. The rest of the ship is represented only by scattered ftagments.
The pictures that emerge bespeak the violence of the implosion event itself
and give mute but eloquent testimony to a law of submersibles: There exists
a maximal depth below which a submarine cannot dive. If this depth is ex-
ceeded, violent, catastrophic implosion ensues.
Almost 14 years to the day after the Thresher's hideous death, I anx-
iously watched a winch do its slow work on the back of a Fij ian fishing boat
sevetal miles off the verdant coast of Viti Levu, the largest island in the Fi-
jian archipelago. The day before, I had caught eight healthy nautilus speci-
mens, creatures at the time more precious (at least to a biologist) than any
gold or silver. I had not counted on such a large haul and had decided to
"bank" them in a closed trap. They had been caught at over 500 meters,
which is about the greatest depth at which these last members of a shelled
cephalopod clan can reliably be caught, and they had been returned to that
depth. But this morning my depth sounder showed that the trap I had low-
ered to 500 meters rested now at 750 meters instead. During the night, heavy
