Critical Zone Observatories Critical Zone Observatories (CZOs) address pressing interdisciplinary scientific questions concerning geological, physical, chemical, and biological processes and their couplings that govern critical zone system dynamics. Observatory Sites US National Science Foundation. See https://www.nsf.gov/funding/pgm_summ.jsp?pims_id=500044 ODM2 SiteType Controlled Vocabulary ODM2 Working Group A vocabulary for describing the type of a data collection Site. To some extent, these types represent the ultimate feature of interest that the site was established to measure. For example, a Stream Site was established to measure properties of a Stream.