In the science of tephrochronology, the Saksunarvatn tephra is volcanic ejecta that formed an ash layer that is useful in dating Northern European sediment layers that were laid down during the Boreal period, the warm climate phase that followed the cold snap of the Younger Dryas as the earth made the transition from the last Pleistocene glaciation to the current interglacial, or Holocene. This was a period of rapid climatic transitions around the North Atlantic, some of which took place during a matter of decades.
Tephrochronology, in the context of volcanic ash layers, is a scientific discipline that uses tephra deposits to date sediment layers. The Saksunarvatn tephra is a type of volcanic ejecta used for dating Northern European sediments during the Boreal period.