Atlantis Diary III
Exploring Alien Eco-Regions
The bizarre hydrothermal vent field discovered a little more than two years ago surprised scientists not only with vents that are the tallest ever seen --the one that's 18 stories dwarfs most vents at other sites by at least 100 feet -- but also because the fluids forming these vents are heated by seawater reacting with million-year-old mantle rocks, not by young volcanism. The field is unlike any seen before, according to chief scientist Deborah Kelley, a University of Washington associate professor of oceanography, and co-chief scientist Jeff Karson, a Duke University professor of earth and ocean sciences. Both have visited fields of black-smoker hydrothermal vents that scientists have been studying since the 1970s.
Now the two scientists who were the first to travel in a submersible to the field after its serendipitous discovery Dec. 4, 2000, are leading a National Science Foundation-funded expedition to map and further investigate the field. The 'Atlantis Diaries' chronicles the expedition returning with 24 scientists onboard an exploration vessel, the Atlantis, during their 32-day expedition that spans April 21 to May 22.
Tuesday, April 29
The second dive of the expedition gave me appreciation for the scale of the landscape that one can only get by being there. Our dive began as they all do: with the systematic run through the safety checklists, climbing down into "the ball," leaving the ship, and descending through the deepening blue into the quiet blackness of the deep sea. It's a fantastic experience no matter how many times you do it.
Phil Forte was our highly capable and hard-working pilot, geologist Jeff Karson was on the port side, and I was tucked into the starboard side. We shifted around from time to time to share looks out of our three view ports.
We touched down at a depth of 870 meters, about 300 meters west of the known warm vents. We were on the side of a steep undersea mountain, where the terrain is extremely rugged and dramatic. We drove the submarine up the steep slope, which is covered with debris sliding down from above, including some curiously uniform, brown, twig-like pieces.
|Atlantis expedition ship, leaving port in Barbados for the North Atlantic ridge
We arrived at the base of a near-vertical cliff. The pilot adjusted the ballast and we began ascending up the face of the cliff, noting changes in the color and texture of the rock. We went up and down the face of this cliff several times during the dive as we made our way from west to east. In the many places that I have visited in the Alvin, I have often wished that the ocean water could be removed so I could walk around to explore the terrain -- but not today. Flying and hovering in Alvin was a fantastic way to view features that would require serious mountaineering skills to see on dry land.
White features in the dark rock are signs of potential hydrothermal activity. We investigated many white carbonate veins and small chimney growths in our traverse. In one promising case, we followed delicate carbonate growths up along cracks in the cliff face, ending in an extensive area of bright white carbonate beneath an overhanging ledge of cemented carbonate breccia. We examined these as closely as we could, but could not find any sign of flowing fluids actively forming these features. Apparently the flow rates here are as slow as the gradual dripping that forms stalactites in limestone caves. We were not able to sample the fluids, but we did bring back a sample of a small carbonate chimney growing out of the side of the cliff.
After exploring and sampling a variety of rocks for six hours, we were running short on time and power, so we drove straight to the gigantic Poseidon carbonate tower. I'd heard how big this feature is, but I was still amazed when I saw it. We started somewhere near the base of this massive tower and followed it up 40 meters to the top.
We quickly filled all of the water samples at a small vent. Using the "slurp" sampler (basically an underwater shop vacuum), we collected swarming amphipods and other small swimmers that seem to gather around the heat of the submarine lights.
Wednesday, April 30
Entry by Jeff Karson
Every time I make a dive in Alvin or see the other members of our group descend beneath the waves I think of how much it is like traveling to another planet in a spaceship.
When we go to the seafloor there is no sunlight, and the only light we have comes from the battery-operated lights on Alvin. With no sunlight, there is no photosynthesis and none of the green plants that we have on land. Because there are no grass, weeds, or trees, the animals that live off them don't exist either.
|The mapping project involves global, regional, local and ultimately microscopic--from the great to the small
Instead of air, we are surrounded by an "atmosphere" of much thicker seawater that is under tremendous pressure because of the great depth. Without the artificial atmosphere sealed inside Alvin, we would stand about as much chance of surviving on the seafloor as we would on the Moon or Mars. Not many animals have adapted to live in this extreme environment, so much of the seafloor looks like a desert. Living organisms concentrate around the hydrothermal vents like the Lost City, an isolated oasis. On the deep seafloor, there are no seasons and no weather. There is only cold water that moves under the influence of deep currents and tides.
My own particular fascination in this alien environment is with the rocks. Even these are different from most of the rocks we see on land, which are parts of the continents. The rocks of the seafloor are mostly darker and denser. Out here near the Mid-Atlantic Ridge, where the oceanic crust is very young (less than 1 million years old; that's young in geological terms) we find mountains of basaltic lavas and peridotite mantle rocks. Huge cliffs, rivaling the walls of the Grand Canyon, have been created by giant fault zones and rock slides. These areas allow us to study rocks that formed deep beneath the spreading center; these rocks form the foundation of the Lost City.
For the fluids that emanate from the spires and flanges, there must be fractures and fault zones in the underlying rock that allow those fluids to flow out to the seafloor. Part of our investigation focuses on understanding this "plumbing system" beneath the Lost City. To do this we are mapping all the fractures that we can find in the area and taking special note of those that allow the flow of hydrothermal fluids.
On another note, the members of the Lost City Expedition would like to congratulate Betsy Williams on her first Alvin dive. As she stepped out of the sub, she received the traditional congratulatory gesture -- several buckets of cold ice water!
Friday, May 2
Entry by Kate Buckman
So far you've been hearing a lot about all the really neat carbonate and serpentinite rocks that we've been finding at Lost City, and a little about the chemistry of the venting waters. Both of these things have an impact on my particular area of interest: biology.
My job on this cruise is to help collect and identify the macrofauna (animals larger than the size of a flea) found at Lost City. We are curious about what lives down there, and if any of the animals are found only at vents in the Lost City or if they are typical deep-sea fauna.
|Where the Earth's mantle meets the crust, temperatures rapidly swing and minerals precipitate out the dissolved solids (carbonates) in the ocean
So what does live there? At first glance it doesn't look like much does. The white rocks seem bare and the shimmering water lacks the abundant animals that I am used to seeing associated with vent fluids at other hydrothermal systems. Yet the Lost City is not devoid of life.
There are many corals surrounding Lost City, as well as the large grouper that like to follow Alvin around. They have to be eating something. Closer inspection reveals what is there. Small purple fish swim lazily around, and large crabs hide in cracks and crevasses.
Swarms of "bugs" above Poseidon are attracted to Alvin's lights. We use a slurp gun to capture these and bring them to the surface. The slurp is full of small shrimp-like creatures and other tiny crustaceans called amphipods. We hadn't seen one type of amphipod before and have taken to calling it a Frankenpod because it looks like bits of other animals all stuck together.
Any animals that we can't identify while at sea are preserved to allow us to identify them when we get back to land. Most of the animals are frozen, and back in the lab we will use their tissues for genetic comparisons to known animals.
Yesterday we didn't sample any biology from Lost City because our samplers wouldn't fit on the basket with the Beast (the large vent fluid sampler). But it was an exciting biology day anyway. Crew members fished two pieces of debris out of the ocean that had been floating along for quite some time and had been colonized by many animals. I spent much of the evening picking crabs, barnacles, and nudibranchs off of pieces of plastic strapping material and a buoy. Many of the geologists couldn't believe that I would actually touch those things, but for me it all part of a day's work. Getting to see all the amazing things that live in the ocean is what makes my job so enjoyable.
The project includes scientists, engineers and students from the University of Washington, Duke University, Woods Hole Oceanographic Institution, U.S. National Oceanic and Atmospheric Administration, Switzerland's Institute for Mineralogy and Petrology and Japan's National Institute of Advanced Industrial Science and Technology. Collaborators include: Jeff Karson, Duke University, Co-PI and diver during the discovery; Matt Schrenk (an astrobiology graduate student at the UW School of Oceanography); P.J. Cimino (a NASA Space grant undergraduate); and John Baross, also a faculty member in astrobiology and oceanography.
Related Web Pages
Atlantis Diaries XI: Encore
Atlantis Diaries X: Reaction Zone
Atlantis Diaries IX: Rescue
Atlantis Diaries VIII: Science Basket
Atlantis Diaries VII: Poseidon's Excellent Adventure
Atlantis Diaries VI: Portal on the Past
Atlantis Diaries V: Hump Day
Atlantis Diaries IV: Eating Iron
Atlantis Diaries III: Exploring Alien Eco-Regions
Atlantis Diaries II: First Dive
Atlantis Diaries I: Leaving Port
Life from Rocky Reaction
Lost City Expedition
Discovery of Lost City vent field-Univ. Washington
Univ. Washington School of Oceanography
Life without Volcanic Heat