How does volcanic ash help date Iceland’s earliest human settlement?

Volcanic ash, known as tephra, serves as a vital tool for dating Iceland’s earliest human settlement through a method called tephrochronology.

Because Iceland has experienced numerous violent volcanic eruptions, these events deposited distinct layers of ash across the landscape. These layers act as time-stratigraphic markers, allowing researchers to correlate geologic and archaeological events.1

Specifically, a distinct layer of tephra has been identified that coincides with the earliest physical remains of human habitation in Iceland. This same ash layer has been found in Greenland ice cores and dated to approximately 870 CE. This scientific evidence aligns with historical accounts from sources like The Book of the Icelanders, which place the settlement of Iceland by Norse people in the late 9th or early 10th century.2