Mail Buoy
May 30, 2003
Hi my name is Leslie Malimali
and I'm from Westborough Middle School I just want to ask you are
there any sharks down there?
We have not seen any sharks yet, but there are a number
of deep-sea sharks known from the area around the seamounts.
We might get a chance to see one of these during our
dives in the sub.
Jon Moore
Scientist
Have any of the crew members seen a sponge yet?
Devon Tucker and Kerrie Garcia
6th grade
Westborough Middle School
South San Francisco
Yes, there are many different sponges out on the seamounts.
Most of them are different species of deep-sea glass
sponges, which have a skeleton of glass-like spines
holding their shape.
Jon Moore
Scientist
Don't ask me why but I was wondering how big and how
long are the octopus that you guys are finding? Have
you found any?
Ms Margaret Lu
Westbrough Middle School
South San Francisco
The octopods are up to 3 feet long from the top of
the mantle (head-like part) to the tips of the arms,
when they are stretched out. The octopods are a bit
wide, so one 3 ft long would fill a 3 gallon bucket.
Jon Moore
Scientist
Are there cool things to see down there besides volcanoes?
Kerrie Garcia
Westbrough Middle School
South San Francisco
Hi Kerrie, There is always something
cool to see under the sea... I'm very lucky to be
an Alvin Pilot and have over 300 dives to the bottom
of the ocean. Every dive brings something new. So
much new in fact we have to ignore it and concentrate
on the mission or all we would do is say "Wow,
what's that? Seen anything like that before? Pretty..."
There are volcanoes, but you can only see little slices
of them at a time. It's dark in the deep ocean, sunlight
only penetrates to around 400 meters. We bring our
own lights on Alvin, but they only let us see about
30 feet. A 30 foot slice of volcano looks like most
other rocky terrain. Unless it happens to be where
lava from a recent eruption has drained away and left
a jagged black glass tower called a lava pillar. I
think they are the prettiest thing on the sea floor.
Also in that 30 feet can be jets of hot black water,
fresh shiny black basalt lava, brown and white sediments,
and even green rocks from under the Earth's crust.
And that's just some of the more colorful geology.
Animals include shrimp (with and without eyes), octopi
(with and without dumbo ears), crabs, clams, mussels
and starfish, a million kinds of worms including the
fastest growing animal on the planet, and fish so ugly
you'd give up eating seafood for life.
And oh yeah, the Titanic. On
this cruise we are supposed to be collecting a kind
of coral called Desmophyllum. It looks like a mushroom.
Actually the scientists want fossils of the "Mushroom Coral".
They will analyze the fossils and see what chemicals
were in the ocean at the time the coral was alive
and growing.
Just when I thought I'd seen it all they come up with
a cruise that is a hunt for a rock that's really an
animal. Not because they are interested in animals
or rocks but because they want to know about the chemistry
of the ocean 70,000 years ago. Nobody just wants fish
anymore...
Take care,
Blee Williams
Chief Pilot, Alvin Group
I have several questions. One, how were the seamounts
originally formed, and what does evidence show is going
on with them today? Also, was there a sweeping subduction
zone that built the volcanoes or was it a series of
hot spots? And, ss there any evidence of chemosynthesis
around the present inactive volcanoes or faults?
Annie Rosinha
Earth Science/Botany teacher
Sandwich High School
Massachusetts
Great questions, Annie.
First, the formation of the seamounts: The seamounts
were formed by a single, fairly stationary hotspot
that rose from deep in the mantle due to being hotter
and more buoyant than the surrounding mantle. As the
ocean plate passed from east to west over the stationary
New England hotspot, volcanoes would form. They would
build enormous shield-shaped mountains, and then become
extinct as they left the hotspot's vicinity. Therefore,
the oldest seamounts, close to the continental shelf
near Massachusetts, are about 100 million years old.
The seamounts are progressively younger towards the
east.
Today, the hotspots are all inactive, with the possible
exception of the Great Meteor Seamount. However, rocks
dredged on the Great Meteor Seamount have been poorly
dated, so it's period of most recent activity is not
known.
Regarding your question about subduction zones:
Based on what we know about the chemistry of subduction
zone basalts, the New England Seamounts are definitely
not subduction related. In addition, there has not
been active subduction in this region since the Devonion
(i.e., when fish evolved), which was over 200 million
years ago. The ancient subduction zone is at least
a factor of 2 too old to have formed the New England
seamounts. Furthermore, because the seamounts follow
a geographical age progression, and because they have
chemistry that is similar to active hotspot volcanoes
today, we infer that the seamounts were formed by a
mantle plume that created a hotspot track.
Regarding your question about chemosynthesis:
Given present knowledge, chemosynthesis requires active
hydrothermal vents to operate in the ocean. Because
there are no hydrothermal vents in the New England
Seamounts, there are probably no chemosynthetic organisms
in the seamount chain. However, if Great Meteor Seamount
proves to be active, it is certain that biologists
will be excited to determine if chemosynthetic organisms
are present there.
Best Regards,
Matt Jackson
Scientist
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