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NeMO
Date:
July 6, 2000
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| Science
Report: ROPOS dive 545 returned to the ASHES high-temperature vent field and visited individual chimneys with names such as Gollum, Phoenix, ROPOS, Mushroom, and Virgin Mound (named because it is a white chimney of anhydrite). A host of items were deployed during the dive, including larval sampling tubes (to learn more about how animals colonize vent sites), a flow meter (to measure the flow rate out of an area of diffuse venting), microbial traps (to sample microbes at vents), and miniature temperature recorders, (MTR) which will record continuously for the next year (photo below). In between deployments, the biologists were busy observing the local residents in the vent field, including octopus, clams, crabs, various species of worms, and holothurians. After ROPOS came up in the morning we deployed a Bottom Pressure Recorder mooring at the center of Axial caldera. This instrument will be down for the next year and will make precise pressure measurements to monitor for vertical movements of the seafloor (caused by inflation or deflation of Axial's magma reservoir), such as the 3 meter subsidence measured during the 1998 eruption. Following this deployment, ROPOS went back in the water for dive 546. This dive was as the southern end of the lavas erupted in 1998 (about 4 miles south of Marker 33). Dive 546 consisted mainly of collecting the first half of a new Imagenex sonar survey. At this southern site, the eruption produced a mound of pillow lavas up to 25 m thick, very different from the 5-m thick sheet flow at the northern end. The high-resolution bathymetry from the Imagenex will show how the morphology of the lava flow at this site differs from the northern end of the lava flow that we have surveyed in previous years. |
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