HR: 16:00h
AN: OS14B-01 INVITED     [Abstracts]
TI: Carson Lecture: Seafloor Hydrothermal Vents and Their Impact on the Composition of the Ocean Crust, Ocean Chemistry, and Biological Activity in the Deep Sea
AU: * Tivey, M K
EM: mktivey@whoi.edu
AF: Woods Hole Oceanographic Institution, Department of Marine Chemistry and Geochemistry, 360 Woods Hole Rd. MS8, Woods Hole, MA 02543 United States
AB: February 1977 marked the discovery of seafloor hydrothermal vents along mid-ocean ridges, and a beginning to studies of their impact on ocean chemistry and biological activity in the deep sea. Evidence for these systems was known from heat flow anomalies and from the rock record in the form of volcanic-associated massive sulfide deposits. The discovery provided a first chance to analyze the hydrothermal fluids, infer the consequences of high temperature water-rock reaction within the ocean crust, and observe interactions of vent fluids with seawater at, beneath, and above the seafloor. Ocean chemists compared vent fluid and river inputs to the oceans and estimated contributions from hydrothermal activity to global chemical fluxes. Study of the vent deposits and their unusual biological communities, however, is not straightforward, requiring consideration of the complex interactions during mixing of two compositionally distinct fluids. The mixing processes are in some ways analogous to those occurring within estuaries, though at vent sites fluids differ not just in salinity but in temperature, pH, and redox state. As in estuaries, mixing is complicated by non-conservative processes. These studies have required more sophisticated geochemical modeling efforts that consider reactions at elevated temperatures and pressures, and diffusion and advection in environments characterized by steep chemical and thermal gradients. In situ measurements are still needed to test the accuracy of these calculations, especially in the temperature and pressure region close to the critical point of water that is typical of many vents systems. The presence of novel organisms that thrive off the chemical energy created by mixing processes has added to the drive to develop in situ sensors capable of making measurements in hostile vent environments. As we approach the end of the third decade of study of seafloor hydrothermal systems, we have only just scratched the surface in our quest to identify the full range of existing vent environments. Much will be revealed about these environments and how they change over short and long time scales with the future use of new in situ sensors and more sophisticated modeling efforts.
DE: 4832 Hydrothermal systems
SC: Ocean Sciences [OS]
MN: 2005 Joint Assembly