Tephrochronology

Tephrochronology is a chronometric and stratigraphic technique that uses volcanic ash layers (tephra) as time markers to date and correlate archaeological and geological deposits. Pioneered by Icelandic geologist Sigurdur Thorarinsson in 1944, it exploits the fact that large explosive volcanic eruptions deposit distinctive ash layers across vast geographic regions instantaneously in geological time. Each tephra layer serves as a chronological marker horizon that can be identified, characterized, and dated, enabling archaeologists to synchronize deposits across multiple sites.