Fishy Biz.........
Underwater Mountaineering
Seeking to Learn How a Huge
Underwater Mountain Formed
Underwater topography of the area
around the Atlantis Massif. Red indicates
shallower areas than blue. The
12,000-foot high mountain along the
Mid-Atlantic Ridge was discovered a few
years ago. (Donna Blackman, Institute of
Geophysics and Planetary Physics, Scripps
Institution of Oceanography, University of
California, San Diego, Earthguide)
By Lee Dye
Special to ABCNEWS.com
Nov. 15 — The research vessel Atlantis
pulled out of the port of St. George in
Bermuda recently and headed off to
sea in search of a mountain.
Scientists from eight universities will spend
a month aboard the ship, based at the Woods Hole
Oceanographic Institution, in Woods Hole, Mass., searching
for clues to a mystery. Their basic question: Why has a
towering mountain risen from the ridges and hills along a
fascinating geological structure called the Mid-Atlantic Ridge?
Far beneath the surface of the ocean, 12,000-foot
Atlantis Massif is nearly twice as tall as other mountains in
the area, and no one is certain why.
During the expedition, scientists will study the mountain
with cameras and sonar, and take turns spending two weeks
aboard the titanium-hulled submarine Alvin, snapping
pictures and collecting rocks for analysis back in their labs.
And the rest of us have been invited to go along for the ride.
Reports from the expedition will be published twice a
week on the group’s Web site, and questions can be
e-mailed to the scientists through their spokesman, Monte
Basgall.
“We pulled out Saturday from St. George, Bermuda’s
quaint first capitol, which is almost four centuries old,”
Basgall tells me by e-mail. The ship set out on a “perfect
morning,” he adds, and within moments the scientists had
turned to the task at hand.
Young, But High Mountain
The Mid-Atlantic Ridge has long fascinated scientists because
it is one of the regions on the Earth — all located under seas
— where new crust is being formed. As the tectonic plates
pull apart at the ridge, hot rocks from below to rise to the
surface and cool into slabs of stone. Many centuries from
now, the forces of nature will use some of those rocks to
build new mountains along the shorelines, constantly
reforming the planet we call home.
The ridge itself is enormous, winding south from Iceland
for more than 6,000
miles, and it is one of the
largest mountain ranges
on Earth. But it is
completely under water,
usually at least 12,000
feet, except for the few
areas where mountains
poke through the
surface. However, most
of the mountains along
the twisted, gnarled
ridge are relatively
modest.
That’s why Donna
Blackman of the Scripps
Institution of
Oceanography in La Jolla, Calif., was so surprised when she
and Joe Cann of the University of Leeds in the United
Kingdom discovered Atlantis Massif while mapping the ridge
a few years ago.
Mountains are common at mid-ocean ridges, but this one
is a dandy. It is four to six times wider than other mountains
in the area, known as abyssal hills, and it towers over its
neighbors like, well, a mountain.
But since it is part of the ridge structure, it must be very
young, geologically speaking, because it was formed from
new crust welling up through the fissures along the ridge,
which is also called a spreading center. Blackman wanted to
know how it got there, and why it was so huge. By most
reckoning, it should be a lot more puny.
She’s the chief scientist on the expedition. Co-principal
investigators are Deborah Kelly of the University of
Washington, an expert on the interaction of fluids with
oceanic rock, and Jeffrey Karson, a structural geologist at
Duke University.
Karson likens the ridge to a “taffy pull.” As the sea floor
pulls apart, it becomes thinner, allowing molten rock to push
through.
“Happening over and over again, that process produces
new oceanic crust, and over geological times it re-paves the
ocean basins repeatedly,” he says.
It is a key part of the renewal process that this planet has
been going through since shortly after it was formed.
Stretching and Breaking
While no one knows why Atlantis Massif is so big, theories
abound.
Some scientists believe the Mid-Atlantic Ridge may be
quite similar to the Southwest part of the United States,
where new mountains are formed as the ground is slowly
stretched apart in response to tectonic forces along the
Pacific seaboard. Huge chunks of rock slowly tilt as the crust
is thinned, forming the Basin and Range Province and other
major mountain ranges.
It is similar to pulling an art gum eraser apart. The
eraser gets thinner in the middle and forms deep cracks
before it breaks. When that happens in the Earth’s crust,
chunks of the “eraser” tilt, lifting one edge up and depressing
the opposite side in a classic mountain-building scenario.
Compounding the mystery, however, is the fact that
earlier researchers found little evidence of lava, the normal
stuff used to build the rocks that form the mountains, so
there may be some sort of additional geochemical process
going on as well.
Exploring by Sonar, Cameras and Alvin
To try to get the answers, the scientists will drag some
sophisticated devices through the water as the ship passes
over the mountain. A side-scan sonar that uses sound waves
to create images, much the same as a camera uses light
waves, will map the entire area. Then they will send a
camera down to capture pictures of the mountain.
And finally, they will take turns going down in Alvin, the
historic submersible that has probed so many of the world’s
oceans. Two scientists and a pilot will be aboard the craft,
which can dive down to 14,764 feet and stay there for eight
hours.
They will use their eyeballs as research tools, gazing
through the 3 1/2-inch thick windows at the steep slopes of
Atlantis Massif. Alvin also has two robotic arms that will
break off pieces of the mountain and bring them home.
When it’s all over, we should have a better understanding
of why Atlantis Massif is so big, and how the forces of nature
go about constantly rebuilding our planet. |
