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Johnson Flow/Temperature Meter Dive 553

On Dive R553, ROPOS deployed a meter to measure the rate of flow and the temperature of fluid rising out of a vent at the Crack Vent at ASHES. The instrument was placed over the site of a unique deepsea construction project completed by ALVIN in 1998 under the guidance of Principal Investigators H. Paul Johnson of the University of Washington and James Cowen of the University of Hawaii. The hot vent fluid emanates from a long crack in the flat lava flows at this site. The rectangular box shown in the photograph was first placed on the seafloor by ALVIN. On subsequent dives, ALVIN actually cemented the box into place on the seafloor! This forms a seal over the vent for several feet on either side of the central pipe, which focusses the flow from the crack and provides a longterm site for instruments. During the first year (for a program funded by the National Science Foundation), the site contained a special column to measure temperature and flow rate and to collect organic matter from the vent fluids. In order to insure continued use of this unique monitoring site in the ASHES vent field, we deployed the instrument seen in the photograph for Paul Johnson. This instrument and the 26 temperature probes we placed at Axial on NeMO2000 will provide key data on changes in the hydrothermal and volcanic system over the next year.