Margaret Kingston (Meg) Tivey, an aqueous geochemist, combines laboratory, theoretical, and field studies to examine the formation of seafloor vent deposits and the transfer of energy and mass through active hydrothermal systems. Born and raised in Lexington, Mass., she majored in geology at Stanford University (after taking a course with five field trips to local beaches and fault zones). As a graduate student at the University of Washington, she was first introduced to seafloor hydrothermal systems when massive sulfide samples, with live tubeworms, were recovered while dredging along the Juan de Fuca Ridgeonly the fifth discovery of an active mid-ocean ridge hydrothermal system. Working on these samples, she received an M.S in geological oceanography in 1983. In 1984 she had her first opportunity to dive in Alvin, and shifted her dissertation to develop a theoretical model to link measured vent fluid compositions to observed mineral assemblages in vent deposits. After receiving her Ph.D. in 1988, she came to WHOI, where she is now an Associate Scientist, studying active vent sites on the Mid-Atlantic and Juan de Fuca Ridges, the southern East Pacific Rise, and in Guaymas Basin using both human occupied submersibles (Alvin, Nautile, Turtle) and remotely operated vehicles. Her studies are aided by X-ray computed tomography (CAT scans) to examine samples of mineral deposits in three dimensions; development and use of numerical models to link vent fluid compositions to vent deposit mineralogy; and collaboration with engineers to develop, build, and use instruments capable of making measurements in the high-temperature and low-pH conditions present at vent sites.