TEMPORAL VARIATIONS IN DIFFUSE HYDROTHERMAL FLOW AT TAG

We have obtained direct measurements of diffuse hydrothermal effluent temperature, velocity and chemistry from the TAG hydrothermal mound, 2 6 degrees 08'N, 44 degrees 49'W, Mid-Atlantic Ridge. We report on the time series physical measurements obtained from a location on the east ern flank of the main summit complex. Several features were observed i ncluding strong tidal variability in flow, a conspicuous elevation of effluent temperatures during the period 11 October - 17 October 1994, and a long term increase in temperature superimposed upon all other tr ends. The six-day-long temperature excursion is coincident with increa ses in sediment and effluent temperatures observed by instruments left in place on the TAG mound by other workers. We have established throu gh time-lapse seafloor video observations and through drilling records that the mid-October effluent temperature excursion is correlated clo sely with local drilling activity by the Ocean Drilling Program.