The East Pacific Rise 8\deg to 11\deg N Integrated Studies Site (ISS); Update and Opportunities

The 8\deg to 11\deg N segment of the East Pacific Rise (EPR) represents a dynamic, fast-spreading type of mid-ocean ridge selected for focused interdisciplinary study within the Ridge 2000 program. Diverse fast spreading environments are encompassed by the site including a hierarchy of axial segments and discontinuities. The site "bull's- eye" is at 9\deg49' to 9\deg51' N where numerous high temperature vents and diffuse flow communities have been mapped and monitored over the past 14 years. Concentric circles around the bull's eye encompass ridge segments at a range of scales, from the first-order segment bounded by the Siquieros and Clipperton transform faults to the fourth-order segment which includes the extent of the 1991 and 1992 volcanic eruptions. Five-year goals for the site include a working model of mantle flow and melt supply; detailed imaging of subseafloor structures and relationships to vent communities and chemistry; quantitative data about microbes and macrofauna and linkages with fluid flow, tectonics, and magmatism; quantification of the heat/chemical flux into the water column; and linkages and temporal variation in geological, chemical, and biological parameters. Field programs in 2002 collected data for calculations of primary and secondary productivity at different vent communities, with a focus on tube worms and bivalves; searched for hydrothermal signals from an earlier earthquake swarm; and continued time-series fluid sampling at all 9\deg10' to 9\deg51'N high-temperature vents. 2003 cruises will continue geophysical/volcanological studies and deploy an array of in situ chemical sensors for use in monitoring vent fluids. Programs scheduled to begin in 2004 include three-dimensional multi-channel seismic and magnetotelluric studies of subsurface structure at the site "Bull's eye", initiation of monitoring studies of seismicity, fluid temperature and chemistry, and vent fauna. An overview of on-going and upcoming studies at the site will be presented.