High-energy cosmic rays shower the Earth's surface,
penetrating meters into rock and producing long-lived radionuclides such
as Cl-36, Al-26 and Be-10. Production rates are almost unimaginably small
- a few atoms per gram of rock per year - yet we can detect and count these
"cosmogenic isotopes" using accelerator mass spectrometry, down
to levels of a few thousand atoms per gram (parts per billion of parts
per billion!). The build-up of cosmogenic isotopes through time provides
us with a way to measure exposure ages for rock surfaces such as fault
scarps, lava flows and glacial pavements. Where surfaces are gradually
evolving, cosmogenic isotope measurements allow us to calculate erosion
or soil accumulation rates.
This site explains some of the background to our work
and provides an overview of cosmogenic isotope research at the University
of Washington. It also serves as a repository for data generated by
the group, descriptions of our lab procedures, technical information and
This web site is partially supported by grants from the National Science Foundation.