Project involves the analysis of approximately 100 heat flow data points taken during the Mariana Mounds ALVIN program in 1987. Measurements include 19 measurements along 5 short multi- penetration profiles, 11 gradient measurements from piston cores and 85 temperature gradient measurements using the ALVIN probe. Raw data will be processed to obtain actual temperatures, thermal conductivity will be estimated from porosity profiles and existing data. Estimates of advective flow rates will be obtained from temperature profile curvatures. The heat flow data coupled with other data should help characterize the Mariana Mounds hydrothermal system. %%% Seafloor hydrothermal systems are a relatively recent discovery of fundamental importance. The heat flux from these systems is an important factor in the global heat budget of the earth and the chemical and mass flux has a significant effect on ocean chemistry, the formation of ore deposits, and the development of biological communities. Little is known about the details of the hydrologic regime of mound structures that are often found at hydrothermal discharge zones. The work to be carried out in this project will help address this problem.