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Into the Deep
Join Karen Von Damm on a voyage to the bottom of the sea
By Robert Kunzig
Once or twice a year, Karen Von Damm boards a ship bound for a place not on ordinary maps, a place known often by its latitude--21 degrees north, 9 degrees north, 21 degrees south. Arrived at that place, in the middle of an ocean, she climbs into a small submarine and dives straight down, a mile and a half or sometimes two. If things work out, she lands on top of an active volcano, dotted with hot springs. Maybe she sees tube worms--tall as ripe corn with blood-red plumes waving in the current--or clouds of shrimp swarming like bees around rock chimneys tall as houses. Out of the chimneys billows 700 degrees Fahrenheit (371 degrees Celsius) water that is black with iron. Sometimes the roiling cloud engulfs the submarine and blacks out its portholes. Von Damm is in her element.
The midocean ridge, the chain of seafloor volcanoes that wraps around the planet for 40,000 miles, is a different world. Karen Von Damm has been going there for more than 20 years, and for the last 10 she has been leaving from Durham, where she is professor of geochemistry at UNH. She is the world's leading expert on "black smokers," as those seafloor chimneys are called. They were first discovered in the spring of 1979 at 21° North on the East Pacific Rise, at the mouth of the Gulf of California. In the fall of that year, Von Damm visited the site with the first scientific team to collect chemical samples at a black smoker. Those samples changed our understanding of the oceans' chemistry forever.
The big question in chemical oceanography is, "What controls the chemistry of seawater?" Scientists want to know why oceans are just as salty as they are, why seawater contains certain chemicals and not others, and where those chemicals come from. "This matters because ocean chemistry largely determines what kind of life can thrive in the sea and how well the oceans can buffer changes in the climate system," Von Damm observes. "We now know that seafloor hydrothermal activity is a big piece of the puzzle."
As water percolates down through cracks in the ocean floor at a hydrothermal site, it is rapidly heated by contact with hot rock, and its chemistry changes radically: some chemicals are removed from the water and others are absorbed from the rock. Then the superheated water blasts back out of the seafloor through a vent, like a black smoker, precipitating minerals as it cools. You can't understand the chemistry of the ocean if you don't understand what happens at hydrothermal vents.
In 1981, Von Damm went back to 21° North to collect the data that would become her Ph.D. thesis--the first basic description of vent chemistry. It was on that cruise that she got her first chance to dive in the submersible Alvin and to see a black smoker up close. She remembers the way the seafloor glittered in the sub's strobe lights. It was covered with fool's gold--pyrite, or iron sulfide--that had snowed out of the inky cloud of water. And she remembers pulling up in front of the smoker itself, a large glittering mound with three chimneys sticking out of it like oversized candlesticks.
"The pilot turned around and said, 'Well, before we start working, why don't we eat lunch?'" Von Damm says. "So we sat there and ate our peanut butter and jelly sandwiches with this black smoker sitting right outside the sub. It reminded me of those old photographs of Victorian scientists in their morning coats, having a little picnic with their umbrellas in front of some fantastic geologic exposure."
A century ago, in Victorian times, there were still fantastic new places to be seen on land.
Today, many people think that the Earth has been fully explored. But there are a few who know that
an unexplored world lies beneath the sea, and who make a point of going there.
If you probe beneath the surface and into the past of an oceanographer, you rarely find a tidy tale of a youth drawn inexorably to the sea. People find their way to the ocean and to oceanography from all over. From Astoria, Queens, for instance. That's where Von Damm spent her childhood. Her father, H.W. Von Damm, still runs a feed and grain business in Brooklyn that was started by his family 150 years ago. Science is not one of his passions. Perhaps her interest in chemistry was sparked initially by her mother, who had been a chemistry major. She did give her only child an unsolicited chemistry set one Christmas. Von Damm remembers it as a disappointment: Mom wouldn't let her do experiments in the kitchen sink.
Science always just seemed to fit the way Von Damm's brain worked. But why did she announce, in junior high, that she wanted to be an oceanographer? She doesn't remember. It wasn't the transatlantic voyage on the Hanseatic, when her parents took her to Germany one summer to discover their roots. Ocean travel was not an instant hit with young Von Damm; she was sick most of the way, in spite of glassy seas. "Luckily I outgrew that," she says.
She was lucky in other ways. Doors opened for her just as she was ready to walk through them. In the late 1960s, when she first announced her ambition to become an oceanographer, women were not even allowed on research ships. But Stuyvesant High School, the highly competitive public school in lower Manhattan that has educated many a scientist, started accepting girls just a year before she was ready to enter. Her freshman class at Yale was one of the first to include a substantial number of women. And the year she graduated from Yale and went off to MIT and the Woods Hole Oceanographic Institution (WHOI) to study oceanography was the year the first hydrothermal vents were discovered off the Galapagos. Her adviser at MIT, geochemist John Edmond, was one of the three people in Alvin when that discovery was made. Von Damm entered the new field of vent research just as it was opening.
Not that Von Damm isn't the sort to push open a door that is closed to her; she is precisely that sort: the determined, confident, self-assured sort. When she speaks in the classroom or in a meeting of research scientists aboard ship, it is without hesitation and without waffling; she doesn't muse aloud. "Karen is a straight shooter," says biologist Tim Shank of WHOI, who has sailed with her for 10 years. "You know exactly what you're working with, and that saves a lot of time."
"Karen is a demanding person in terms of what she expects from her colleagues and students--things need to be done correctly," says Dan Fornari, a marine geologist at WHOI who has been on 10 cruises with Von Damm over the past decade. "She's always super careful in her analyses. If she publishes a number you can take it to the bank."
Von Damm expects the same seriousness and attention to detail from her students. She's not the sort of professor you would try to snow--not more than once, anyway. But the experience and excitement she brings to teaching can change forever the way students feel about science. "This is the first time I have been excited about a science class," one student recently wrote in a course evaluation for Introductory Oceanography. "And I owe it all to the instructor." Another student summed up her impression of Von Damm's analytical geochemistry course in a single word: "WOW!"
Von Damm's time at sea is devoted to collecting water and mineral samples from hydrothermal vents, which means diving in Alvin. It is no picnic, in spite of the sandwiches and the great view. Alvin's titanium passenger sphere is only slightly wider--six feet--than Von Damm is tall, and she has to share that cramped space with a pilot and another scientist. ("She folds up pretty well," says Shank.) A dive typically lasts around eight hours, but half of that is travel time to the seafloor and back. On the way down, the temperature in the sub drops from steambath (if the dive site is in the tropics) to refrigerator (the water temperature at the seafloor is just above freezing). The scientists don wool sweaters and socks; they stare idly at the flashes of bioluminescence emitted by gelatinous animals (most of them unknown) that float past the portholes; and they listen to CDs. There are no toilets in Alvin, only plastic bottles, which makes some passengers hesitate to drink the coffee provided with the picnic lunch.
While the sub is puttering around on the bottom at a knot or so, the scientists are hunched over, each peering out her small downward-pointing porthole, muttering observations into a tape recorder and taking notes by flashlight. (The sub's inside lights are switched off to permit a better view of the outside.)
The black smokers Von Damm is looking for come in all shapes and sizes. At birth a smoker is just a hole in the ocean floor, belching out a pulsing black cone of metalliferous water. But as the metal sulfides hit the cold seawater and snow out of the smoke, a chimney grows like a stalagmite. The chimneys can grow very tall; there is one off the coast of Washington that is as tall as a 16-story building. Some smokers are needlelike spires; others are like candelabra. Some are giant crenellated and turreted masses, with smoke-like black water pouring from dozens of orifices, so they look like burning cathedrals.
Von Damm typically directs the pilot to the hottest orifice--after all these years, she can guess the temperature from the behavior of the plume of smoky water. With Alvin's robotic arm, the pilot plunges the nozzle of Von Damm's titanium sampling bottle deep into the orifice. The idea is to get the purest possible samples of the hot water emerging from the seafloor, before it has been diluted by the cold seawater.
Back on the ship Von Damm will analyze her samples for salt, metals and hydrogen sulfide, the
staff of life at vents. Later she will take the samples back to her lab at UNH for further
analysis. She has a whole wall of samples neatly arranged on shelves in the lab in Morse Hall, each
one meticulously labeled and dated. "This is my water library," she says. "It's irreplaceable."
Von Damm has gotten to know the port of Manzanillo, Mexico, very well over the past 20 years. It's the most convenient port to 21º North and to 9º North, a hydrothermal vent site she has visited seven times. The first time she went, in April 1991, the volcano there had just erupted. Never mind the danger involved in nosing around it in Alvin--what luck! No one had ever seen such an event before.
"There was hot water coming out everywhere on the seafloor," she says of her voyage to the bottom of the sea. "Usually you see it coming out of a few cracks. Here it was everywhere, and it had this white stuff in it. It was literally like driving through a blizzard--not a snowstorm, a blizzard. The seafloor on a ridge is usually black, but here it was all white. It was amazing!"
The white stuff was bacterial matter, and in some places geysers of it were shooting 150 feet above the seafloor. When the researchers weren't in white-out conditions, they were sometimes bumbling through clouds of inky black water. At one place, driving around in Alvin, Von Damm discovered tube-worm corpses protruding from fresh lava. She and her colleagues named that site the Tube-worm Barbecue. The eruption had wiped out a community of hot-springs animals.
But in so doing it had paved the way for an astonishing rebirth--which the researchers were there to see, as they returned to 9° North repeatedly during the 1990s. Tube worms recolonized the site almost immediately; within a couple of years they were five feet tall. Where black water had at first been pouring out of holes in the seafloor, chimneys grew as much as 15 feet tall in a single year. "Things are supposed to happen really slowly in the deep sea," Von Damm says. "And what we found is that this system changes really fast. That's amazing."
On that first cruise in 1991, Von Damm found one smoker whose water temperature rose from one week to the next, until finally it was 757 F (403 C)--a deep-sea record. What she had sampled was deep-sea steam: the water had boiled under the seafloor, separating into liquid and vapor phases, only it was under so much pressure, more than 250 atmospheres, that the vapor looked like a liquid. Von Damm had been arguing for years that deep-sea boiling must happen, but many people hadn't believed her, including her former adviser, John Edmond. Edmond was on the ship in 1991, and he and Von Damm had been debating the subject vehemently right up until the evening Von Damm climbed out of Alvin with proof.
In 1998 on an expedition to 21º South on the East Pacific Rise, Von Damm found a black smoker that was even hotter. This one, labeled "Brandon," was gushing 761 F water. "This smoker was 11 meters high, and the really neat thing about it was that it had vapors coming out the top and brine coming out the bottom," Von Damm says. (Brine is the salt- and metal-rich water that is left behind when the vapor boils away.) When the chemical soup created by the interaction of seawater with hot oceanic crust separates into those two phases, the brine has a tendency to remain trapped in the crust, while the vapor escapes into the sea. The degree to which that happens at hydrothermal vents has a big effect on the amount of the various elements that are injected into the water--that is, on the numbers Von Damm is after. At this site she could observe the effects of the boiling as it happened right there inside the smoker.
At 761 F and a pressure of 283 atmospheres, Brandon was also close to something magical in seawater chemistry--something called the critical point. The critical point, 764.6 F and 298 atmospheres, is where brine and vapor merge into one indistinct phase. The physical properties of that phase are strange: suddenly the water becomes able to transport huge amounts of metals. "The solubilities basically become infinite," Von Damm says. To observe seawater right at that point--which no one has done--Von Damm needs to find a smoker just a little hotter and deeper than Brandon. Groping for ways to explain why that would be so much fun, she gets almost dreamy, and dreamy is not a word you would ordinarily associate with Karen Von Damm.
In January, Von Damm headed back to Manzanillo and back to her old haunts: to 9° North and to 21° North, where she began. People say the black smokers at 21° North haven't changed, but Von Damm doesn't believe it, and no one has checked them in a decade. Sometimes she thinks she might be getting bored with black smokers after 20 years--until she tries to think of something more interesting to do. She has been up and down the East Pacific and the North Atlantic and even into the Indian Ocean, but she is far from finished. "I'd like to go hotter and deeper," she says. ~
Robert Kunzig is the European editor of Discover magazine. His book Mapping the Deep won the Aventis Prize last June
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