I am really surprised a new paper in Nature did not receive more press given its potential to create a shift in how we view hydrothermal vents. The new work by Tolstoy et al. (Columbia University’s Earth Observatory in New York) reports on data gathered from seismometers placed over a 4 square km area in the East Pacific Rise, about 800 kms (500 miles) southwest of Acapulco. Through seismic data, tremors were intriguingly clustered around where the cold water entered the rock, the team was able to construct an image of how water circulates though vent systems.
Old Hypothesis: The pressure of water in the deep sea forces seawater through though large faults occurring along oceanic ridges. The water is heated by volcanic rock and re-emerging in the ridge as a hydrothermal vent. Vents cells are oriented perpendicular to the ridge axis (across axis orientation).
New and Improved Hypothesis: Water travels through a system of minute fissures at a rate much higher than previously thought. In this specific example, the water descends down some 700m into the crust where it fans out 200m before it plunges down another 600m. There it comes near a bulge of magma where it heated and disgorged along a ridge through a dozen vents. The enigmatic quakes are caused by the physical stress of cold water passing through hot rocks. The works also suggest that vents are confined to areas were there is permeability generated by tectonic fracturing. The work also implies vents are oriented along (i.e. parallel) the axis.
More at NSF Discoveries
M. Tolstoy, F. Waldhauser, D. R. Bohnenstiehl, R. T. Weekly. & W.-Y. Kim (2008) Seismic identification of along-axis hydrothermal flow on the East Pacific Rise. Nature 451: 181-184
