California Volcano Observatory

Argon Geochronology Laboratory

Laboratory computers and equipment.

Argon geochronology lab in Menlo Park, California.

(Credit: Jessica Ball, CalVO. Public domain.)

Building 9G, contact Mark Stelten

Geochronology laboratories in Menlo Park provide absolute age control for a wide variety of USGS projects. The laboratories are world renowned for high-quality results on difficult samples and for careful work to develop new techniques and interlaboratory standards. Geochronologists use high-precision 40Ar/39Ar, conventional K/Ar, and Rb/Sr techniques to date rocks ranging in age from 10,000 years to billions of years old. Recent results have placed precise and reliable time constraints on tectonic events, volcanic systems, and ore deposits. In recent years, the emphasis has been on dating young (10,000 to 200,000 years) volcanic deposits from active centers to understand rates of volcanic growth and geochemical evolution and to constrain volcanic hazards. The laboratory has recently purchased a new multicollector noble-gas mass spectrometer and is developing a custom argon extraction line to date younger rocks with higher precision.


Mark Stelten

Research Geologist
Volcano Science Center
Phone: 650-329-5213