Tube worms at Endeavor Hydrothermal Vent Field, northeastern Pacific Ocean. Photo courtesy of NOAA
At the mid-ocean ridges, spreading zones where sea floor is pulled apart by the movement of adjacent tectonic plates in opposite directions, lava from Earth's interior spills into the gash, creating new landscape of oceanic crust. Hot, sulfide-laden fluid courses through subterranean lava pipes, shooting upwards in scorching, chimney-building geysers or percolating through more diffuse vents. And life quickly colonizes the hydrothermal vent fields: bacterial mats look like white paint splashes on a black floor; in the Atlantic, masses of blind shrimp swarm the vents; in the Pacific, giant red-plumed tube worms feed the bacteria they harbor by clustering near sulfide-rich waters.In fact, throughout the world's oceans, an assortment of unusual invertebrates, often astounding versions of familiar characters like snails, crabs, and lobsters, reside at hydrothermal vents in proximity to an underwater realm akin to hell.
Shrimp and crabs grazing bacterial mats on rocks near hydrothermal vents. Mariana Arc region, Western Pacific Ocean. Photo courtesy of NOAA.
Now new technology brings this world into focus like never before. In a session entitled "Doing Fieldwork on the Deep Seafloor," scientists at the 2011 American Geophysical Union (AGU) meeting in San Francisco described findings revealed by better access through torpedo-like autonomous underwater vehicles (AUVs), as well as improved cameras and multi-beam side-scan sonar, and in some cases, data processing that converts multiple 2-D images to 3-D renderings, which can be rotated and viewed at various angles. Together, these and other developments are contributing to intricate imaging and mapping accuracy never before achieved.
Minerals precipitated from hydrothermal vent fluids, photo courtesy of NOAA
For example, in summer of 2011, the Monterey Bay Aquarium Research Institute (MBARI) used the AUV D. Allan B to map fresh lava coverage of the seafloor. An area 10 million square meters large was mapped with astonishing horizontal resolution of one meter and vertical resolution of 20 centimeters, revealing the exact flow boundaries, lava pillars, and small flow features such as lava pillows. As presented by Bill Chadwick, et al., high-resolution bathymetry via the AUV also revealed further detail of earlier flows previously observed from visual features alone. According to their abstract, imaging of downslope ends of 1998 flows "show that large lobes of lava covered with pillows that are 200-500 meters in diameter, 10-20 meters thick" are arranged like shingles on a roof, and importantly, "show clear evidence of an inflation and drainout." Such observations imply surface hydraulic connectivity to an extent larger than that previously assumed for submarine lava flows.
Additionally, armed with high resolution, accurate maps and improved GPS for precise navigation, scientists can obtain samples of rocks, sediments, and biota from exact locations. As presented by Jennifer B. Paduan, targeted sampling by remotely operated vehicles (ROVs) permits scientists to age flows from rocks collected through coring and to follow changes in specific areas over time.
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