A log of elemental concentrations derived from the characteristic energy levels of gamma rays emitted by a nucleus that has been activated by neutron bombardment. The carbon-oxygen log, elemental capture spectroscopy log, pulsed neutron spectroscopy log, aluminum activation log and oxygen activation log are all examples of activation logs. However, the term is most commonly used to refer to the aluminum and oxygen activation logs, the latter also being known as a water-flow log.