Cave’s climate clues show ancient empires declined during dry spell

University of Wisconsin-Madison: The decline of the Roman and Byzantine empires in the Eastern Mediterranean more than 1,400 years ago may have been driven by unfavorable climate changes.

Growth bands are visible in a polished cross-section of a stalagmite from Soreq Cave near Jerusalem, Israel. Stalagmites form from calcite and other minerals deposited by water in caves and contain chemical signatures of the climate and other physical conditions that existed as the formation grew. Geochemical analysis of a similar stalagmite from the same cave has revealed that large climate changes in the Eastern Mediterranean 1,400 years ago, including increasingly dry weather from 100 A.D. to 700 A.D., may have contributed to the downfall of the Roman and Byzantine Empires in the region.

Based on chemical signatures in a piece of calcite from a cave near Jerusalem, a team of American and Israeli geologists pieced together a detailed record of the area's climate from roughly 200 B.C. to 1100 A.D. Their analysis, to be reported in an upcoming issue of the journal Quaternary Research, reveals increasingly dry weather from 100 A.D. to 700 A.D. that coincided with the fall of both Roman and Byzantine rule in the region.

The researchers, led by UW-Madison geology graduate student Ian Orland and professor John Valley, reconstructed the high-resolution climate record based on geochemical analysis of a stalagmite from Soreq Cave, located in the Stalactite Cave Nature Reserve near Jerusalem.

…Using oxygen isotope signatures and impurities — such as organic matter flushed into the cave by surface rain — trapped in the layered mineral deposits, Orland determined annual rainfall levels for the years the stalagmite was growing, from approximately 200 B.C. to 1100 A.D. Their detailed climate record shows that the Eastern Mediterranean became drier between 100 A.D. and 700 A.D., a time when Roman and Byzantine power in the region waned, including steep drops in precipitation around 100 A.D. and 400 A.D….

Growth bands are visible in a polished cross-section of a stalagmite from Soreq Cave near Jerusalem, Israel. Geochemical analysis of a similar stalagmite from the same cave has revealed that large climate changes in the Eastern Mediterranean 1,400 years ago, including increasingly dry weather from 100 A.D. to 700 A.D., may have contributed to the downfall of the Roman and Byzantine Empires in the region.