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Eden in the Depths
Nine Degrees North, East Pacific Rise, is an unassuming address in the Pacific Ocean. The name barely describes the place, indistinguishable on the broad expanse of unbroken sea. To the person gazing from a ship, the water—warm, clear, and seemingly empty—gives no hint of the strange and exotic world concealed in the depths. The near freezing, sunless realm of the deep sea has long been considered one of earth's most hostile environments, inimical to life itself. Yet, 400 miles (640 km) off the coast of Mexico, on the seafloor at Nine North, there lies a lush and vibrant oasis teeming with animals. To the uninitiated, the environment is forbidding and the animals odd, but it was here in the hot springs of the deep sea that earth's first life may have emerged.
Nine North can be a violent place, wracked by earthquakes and erupting volcanoes. Here the planet is giving birth; its youngest seafloor is being formed. Draped over the young rocks are mats of bacteria whose ancestors are almost as old as the earth itself. Young and old are partners here at Nine North, and at hundreds of other hot springs found throughout earth's ocean. There earth's primordial life forms and its youngest, newest ocean floor together nourish communities that continually shatter our assumptions about what sustains life. They are a living reminder of how little we really know the waters covering two-thirds of our planet, and how much life and the forces that give birth to the ocean are linked.
Pulses in the Deep
Geology is the foundation: in the hot springs of the deep sea, life emerges, literally, from rock. The process began early in earth's history, when the surface of the cooling planet cracked. Today earth's crust is broken into approximately seven giant pieces and a host of smaller ones. The plates drift, carried by heat from deep within earth's core. Where they move apart, molten rock rises, building chains of black, undersea volcanoes that circle the globe like the seams of a baseball. They are the longest mountain range on earth, but few people have scaled their summits or walked their valleys. Mostly unseen and unheard, mid-ocean ridges account for 90 percent of earth's volcanic activity. From them the sea is born.
Nine North sits astride these mountains of the sea in the East Pacific Rise, at the border between the Pacific Plate, earth's largest, and the Cocos Plate, one of the smallest.
As these plates separate, by 4 to 4½ inches (11 to 12 cm) each year, molten lava rises to fill the gap, building the new edge. The eruptions and accompanying earthquakes are invisible beneath the waves, muffled by the weight of water, but seismometers resting on the seabed take their pulse. It is unsteady.
Nine North trembles, struck by two or three earthquakes each day, but sometimes its heartbeat quickens. Beginning in 2003, first tens and then hundreds of earthquakes cracked the seafloor daily, hinting at an impending eruption. Scientists monitoring the site in the spring of 2006 were unable to retrieve eight of twelve seismometers.
The data they did recover explained why. Beginning at 13:45 Greenwich mean time on January 22, as many as 250 earthquakes wracked the seafloor each hour. Lava welled up out of the depths, spreading over 1.1 mile (1.8 km) and burying the seismometers, each the size of a microwave oven, in earth's youngest terrain.
More was buried than scientific instruments. By sheer luck, in 1991 scientists had witnessed the immediate aftermath of an earlier volcanic eruption at Nine North, their first on a mid-ocean ridge. Peering from the portholes of Alvin, a deep-diving submersible whose titanium shell protected them from the crushing pressure at 8,270 feet (2,520 m), they saw the newborn seafloor: only days before, within the space of about two hours, approximately 400,000 truckloads of lava had been added to the seabed. Death and devastation accompanied creation. The young seafloor was fresh and glassy, but the animals were dead and dying. Mussels were shattered, blown apart by the eruption. Bits and pieces of dismembered tubeworms, scorched and charred by the heat, littered the seabed. A partially cooked limpet lay near traumatized tubeworms whose days were numbered. The kill was so fresh that the victims had yet to decompose, and scavenging crabs had yet to arrive. Scientists nicknamed the site the "Tubeworm Barbecue."
Life Reemerges from the Ruins
Death, despite its gruesome appearance, did not linger. The upheaval that builds an ocean also renews and replenishes life, delivering an infusion of energy-rich water.
The source of this elixir is a chemical reaction between rock and water, made possible by the moving earth. The reaction begins as icy seawater percolates through young, cracked seafloor, heats up, and turns acidic. At 660 to 750 degrees Fahrenheit (350400°C), it leaches copper, iron, and zinc from the surrounding rock, becoming a corrosive liquid barely resembling water. Buoyant, and laden with metal, the scalding jet of fluid rises and breaks through the seabed. As it hits the chilly water, metals rain out in billows of black smoke, constructing chimneys and towers around the vents. From this poisonous brew, life emerges, and scientists at Nine North bore witness.
The setting was more Hades than Eden. The temperature in the "black smokers," as they are called, had risen to 757 degrees Fahrenheit (403°C), and the vent water was laced with brimstone. Toxic to humans, this hydrogen sulfide is manna from heaven for bacteria that spewed from chimneys and cracks in the seafloor, shrouding Alvin and its passengers in a blizzard of white. Feeding on hydrogen sulfide, the bacteria quickly grew into thick mats carpeting the young rock. Unknown, unnamed, they would become the foundation for life that would rise and flourish from the destruction. Scientists called the site "Phoenix."Smithsonian Ocean
Excerpted from Ocean: Our Water, Our World by Deborah Cramer
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