Dr. Karl Turekian’s lab has used radiogenic and cosmogenic tools to address problems as diverse as the circulation of Long Island Sound and the cosmic dust flux to our planet. The tectonic history of the past 100 million years is inferred from Os isotope measurements in deep-sea deposits. The measurement of 222Rn(3.4 d), 226Ra(1620 y), 228Ra(5.7 y) and 224Ra(3.6 d) in Long Island Sound water profiles provides information on the mean residence time of water in the Sound as well as the flux of nutrient-rich water from the New York City area. The radium isotopes also indicate the horizontal mixing rates in the Sound. The 222Rn and radium isotopes measured in groundwaters also indicate the retardation factors affecting the movement of cations, some of interest in nuclear waste disposal studies. The cosmic dust flux to Earth is determined from the Os flux with the unique meteoric 187Os/186Os. Comparison with another cosmic dust tracer, 3He, provides information on the transport of different size components of the dust through the atmosphere and the oceans before reaching the ocean floor. 87Sr/86Sr of sea water and streams have been shown by others to be a way of translating this ratio into the salinity of coastal waters. Applications to environments of the Mesozoic provide the possibility of working out the life habitats of ancient coastal organisms. Planetary degassing as seen through the study of radiogenic 40Ar provides clues to the rates of recycling of carbon and water through the mantle. These evaluations depend on understanding the composition of the crust and direct measurements of 40Ar flux from the solid earth to the atmosphere. Oxygen isotope signatures preserved in seawater phosphate and phosphatic deposits such as fish debris provide information on the sites of enzymatic equilibration in the water column, and consequently paleothermometry of ancient marine fish habitats.