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VonWilliam J. Broad
Imagine a volcano. Now imagine your main vent being extended in a line. Now imagine that this line is so long that it runs more than 40,000 miles through the dark corners of all the world's oceans, encircling the globe like the stitching of a baseball.
Welcome to one of the planet's most obscure but important features, more prosaically known as the mid-ocean ridges. Although they are long enough to circle the moon more than six times, they get little attention because they lie hidden in complete darkness. Oceanographers discovered its volcanic nature in 1973. Since then, expensive expeditions have slowly explored the underwater world, which is typically more than a mile deep.
The results can make Jules Verne's visions seem rather tame.
The ridges feature long fissure valleys and at their center vast fields of bubbling hot springs that spew tons of minerals into the icy seawater and slowly build eerie mounds and spiers that can be rich in metals like gold and silver. A gnarled tower in the Pacific Ocean nicknamed Godzilla grew 15 stories tall. Thickets of snake-like tubeworms and other strange creatures often cover hot spots, as do hungry scavengers like spider crabs.
The hustle and bustle of life coexists with springs hot enough to melt lead or the plastic windows of mini submarines. With extreme care, humans and robots have measured temperatures up to 780 degrees.
So far, studies have been carried out episodically. Ridge Expeditions undertake erratic excursions, their schedules dictated by the weather and fluctuating budgets, not to mention the whims of the crew and the availability of equipment.
Now scientists have inaugurated an important new effort. Off the west coast, they have wired a highly active ridge with hundreds of sensors and cameras, as well as cables that send the readings to the coast. The ocean observatory will operate for at least a quarter of a century, replacing sporadic flashes with continuous observation.
This month the data wave hits the internet. Hundreds of scientists around the world will now be able to monitor one of Earth's most disturbing and enigmatic features as simply as reading your email.
"We're seeing it come to life," said Maya Tolstoy, a marine geophysicist at Columbia University's Lamont-Doherty Earth Observatory. It recently received a preview that included a rash. "It's exciting," he added. "We're beginning to understand what's happening."
John R. Delaney, an oceanographer at the University of Washington who conceived the observatory decades ago, said it would help scientists better understand not only volcanic ridges but also the surrounding waters that cover most of the planet.
"Suddenly, a technological door was opened to study the ocean from the inside," he said in an interview. The new perspective, he added, "is the only way we'll ever understand its true complexity: the hundreds of processes."
A key question is to what extent volcanism changes over time. The old idea was that lava eruptions and associated activity occurred at a fairly constant rate. Now, studies are pointing to outbursts large enough to affect not only the character of the global ocean, but also the planet's temperature.
Experts believe the activity could have a big impact, as mid-ocean ridges account for about 70 percent of the planet's volcanic eruptions. That, by definition, makes them huge sources of heat and exotic minerals, as well as everyday gases like carbon dioxide, which all volcanoes emit.
"It's a whole new perspective on how the Earth works," said Daniel J. Fornari, senior scientist at the Woods Hole Oceanographic Institution in Cape Cod, Massachusetts. "We have our eyes and ears on a part of the seabed that's really dynamic."
The source of all this activity is the slow churning of the Earth's molten interior, which is constantly rearranging the roughly two dozen plates of the planet's crust. Volcanic ridges mark the places where oceanic plates are slowly pulling apart, providing an escape route for molten rock and gases.
The first volcanic evidence came to light in 1973 when mini-submarines plunged into the mid-Atlantic ridge. It stretches nearly 10,000 miles, making it the longest mountain range on earth. The Franco-American team expected to see the rocky folds and fissures typical of regions on Earth where plates are drifting apart, known as divergent boundaries. Instead, they found beds of hardened lava.
Excitement mounted in 1977 when an American submersible fell off a deep ridge off the Galapagos Islands. Through a hydrophone on the seafloor, a bewildered scientist informed the mother ship that, contrary to usual depictions of the desert-like deep sea, the volcanic site harbored an abundance of life.
"There are all these animals down here," the expert said.reported. The unexpected fauna included red shrimp, brown clams, pink fish with wavy tails, and dense populations of tubeworms with bright red feathers.
In the 1980s, scientists discovered that hot springs can emit huge plumes of warm, floating water. It turned out that zooplankton, clouds of tiny sea creatures, thrive in the mineral-rich plumes. Tracking whale calls suggested the giant mammals fed on the dense schools.
Last year, a more fundamental discovery came to light. A team of 11 scientistsreportedthat the scorching hot springs act as global recycling centers, converting the complex carbon from centuries of dead ocean life into much simpler chemicals that can form new organisms.
"They replace it with material that's biologically reactive," said Jeffrey A. Hawkes, a marine chemist at the University of Oldenburg in Germany who led the research. "You are the soul of the depths of the sea."
Beginning in the 1990s, oceanographers got a taste of what continuous surveillance had to offer when the Navy shared its secret network of underwater microphones used to track enemy submarines during the Cold War. Suddenly marine scientists could listen to volcanic eruptions and study their consequences.
Recently Dr. Tolstoy of Columbia University used acoustic data from nine seafloor eruptions over nearly two decades to painta group portraitfull of surprises. It turns out that all of these eruptions in the Pacific, Atlantic and Arctic oceans happened from January to June.
He suspected the slightly elliptical orbit of the earth around the sun to be the cause. This changes the strength of the Sun's gravitational pull on Earth throughout the year and, as a result, the strength of the tides that squeeze the planet. She said the eruptions coincided with the annual pause in contraction. Even bolder, Dr. Tolstoy suggested that such mechanisms might help explain how the planet's regular ice ages ended so abruptly, long a mystery.
Sea levels drop sharply during periods this cold as water becomes trapped in vast continental ice sheets. Ina piece of paper, suggested that the reduced pressure on the burrs could cause them to erupt much more frequently. As a result, more carbon dioxide would be spewed into the ocean and eventually into the atmosphere, trapping more heat and warming the planet.
In short, according to this hypothesis, the ice sheets would eventually grow large enough to begin their own destruction and replenish the oceans. It was a radical idea that sparked debate.
In an interview, Dr. Tolstoy that increasing evidence from the seafloor suggested that volcanic ridges are "exquisitely sensitive" to small changes in loading, making them vulnerable to a variety of celestial influences. Scientists say these factors could one day improve their understanding of why Earth's climate has changed so significantly over the centuries, and improve their computer models and forecasts.
The underwater observatory promises to help scientists solve such mysteries by examining hundreds of ridge features.
It is on the Juan de Fuca ridge. The center of volcanic expansion, more than 300 miles long, lies on a sloping line off the west coast from British Columbia to Oregon. The observatory is divided into two parts. Canada operates the northern and the United States the southern, part of a larger program known asOcean Observatories-Initiative.
In all, it cost about $500 million, far less than the next generation of optical telescopes under construction around the world. The National Science Foundation, the federal government's major funder of basic research, paid for the US portion.
Together, the two sites have more than 1,000 miles of cable, dozens of junction boxes, and hundreds of sensors.
Instruments on the seabed include inclinometers, cameras, seismometers, temperature gauges, hydrophones, chemical probes, pressure sensors, and liquid samplers. In addition, mobile platforms move up and down long moorings to get higher readings in the water column. The observatory's main cables run to Port Alberni on Vancouver Island and Pacific City, Oregon.
"We have the most advanced wired observatory on any volcano in the world's oceans," said Deborah S. Kelley, a University of Washington scientist who leads the US segment. "There will be many discoveries."
dr Kelley joined Dr. Fornari of Woods Hole and three other marine scientists to put together a photo atlas summarizing what scientists have learned about the hidden world so far.
„discover the depth', published by Cambridge University Press in May, is packed with hundreds of images of extraterrestrial creatures, as well as volcanic spiers spewing clouds of superheated water rich in metals and minerals. It details more than a dozen hot spots around the world, including those on Juan de Fuca Ridge, home of Godzilla. Oceanographers, the book says, have discovered vast swarms of unusually hardy microbes thriving in dark volcanic waters at a temperature of 250 degrees, hotter than most boiling waters on Earth.
Looking ahead, the authors describe the observatory and its importance in viewing the ocean from within. The investigations, so the conclusion, "are still in their infancy".
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