John Walther graduated from Oberlin College where he received a B.A. with a double major in Geology and Mathematics in 1972. He continued his studies doing graduate training at the University of California at Berkeley, receiving a M.A. in 1975 and a Ph.D. in 1978. During his graduate studies he spent a year in Switzerland looking at metamorphic rocks in the Alps. Dr Walther spent 2 years at Yale University as a J. Willard Gibbs Instructor before taking a position at Northwestern University as an Assistant Professor. He remained at Northwestern for 14 years where he rose to the rank of Professor, served as Chair of Geological Sciences and was the Founding Director of the Environmental Science Major Program. In 1994 he moved to Dallas, Texas to become the Matthews Professor of Geochemistry. He uses a unique large volume hydrothermal apparatus to measure mineral solubilities at supercritical temperatures and pressures. Walther also has a wet chemical laboratory to look at rates of reactions between minerals and solutions at near earth surface conditions and to characterize the adsorptive properties of mineral surfaces.

GEOL 3366. ENVIRONMENTAL GEOLOGY AND GEOCHEMICAL CYCLES. An introduction to the physical and chemical processes occuring in the earth's atmosphere, oceans, rivers and groundwater at both a local and global scale. Topics include the climate system, acid rain, global warming, mineral resources, energy and the environment, ozone, hazardous organics, heavy metals and the geochemical cycles of H20, carbon, nitrogen, phosphorous and sulfur. Prerequisites: High school algebra and chemistry as well as one 1300-level course in Geological Sciences.

GEOL 5384. HYDROGEOLOGY. An introduction to the chemical and physical behavior of natural waters and the role of fluids in geologic processes. The course covers evaporation and precipitation processes, runoff and stream flow, aquifers, Darcy's law, equations of flow, regional groudwater flow systems, principles of aqueous geochemistry, oxidation potential, solute and particle transport, and contaminant hydrogeology. Prerequisites: MATH 1338 and CHEM 1304 or consent of instructor.

GEOL 5386. GEOCHEMISTRY. A survey of geochemical processes withing the Earth and at the Earth's surface, emphasizing mineral-water interactions and application of the principles of chemical equilibrium to solution of geochemical problems. Topics include carbonate and silicate equilibra, crystal chemistry, mineral surface chemistry, thermodynamics, oxidation and reduction, isotope geochemistry, reaction rates, metamorphism, and crystallization of magmas. Prerequisites: CHEM 1303 and 1304.

GEOL 6370. AQUATIC AND MINERAL-WATER INTERFACE GEOCHEMISTRY. Chemical equilibria and kinetics in natural water and at the mineral-water interface to help understand the distributions of aqueous species at and near the earth's surface and man's influence on them. Prerequisites: GEOL 5338 or 5386 or consent of instructor.