The tunnel’s age had been debated by biblical scholars, a few of whom had suggested it was built centuries later. The only surviving clue to its age had been an inscription discovered in 1880 on a tunnel wall, which supported the link to Hezekiah but did not specifically name him.
In the new study, analysis of stalactite samples from the ceiling of the Siloam Tunnel and plant material recovered from its plaster floor both confirm the biblical record, researchers say.
“We believe this point is now clearly settled,” said Amos Frumkin, a geologist and director of the Cave Research Center at Hebrew University in Jerusalem. He and colleagues present their analysis in Thursday’s issue of the journal Nature.
Hershel Shanks, an expert on the history of Jerusalem who writes for the Biblical Archaeology Review, said “it’s nice to have scientific confirmation for what the vast majority of biblical scholars and archaeologists believe.”
Shanks, who didn’t participate in the new study, said confirmation of the tunnel’s age was important because so little scientific testing has been done to date biblical structures.
“If you can couple various technological capabilities and science with more traditional scholarship and other historical analysis, and reach the same conclusion, that’s a pretty powerful argument,” said Bruce Zuckerman, a University of Southern California religion professor and expert in biblical archaeology.
Testing is difficult, they say, because sample material from buildings and structures mentioned in the Bible are hard to identify and may be poorly preserved, or access by scientists may be restricted for political or religious reasons.
The tunnel’s plant fragments were subjected to radiocarbon dating, which measures age by the decay of a radioactive form of carbon. Core samples from the stalactites underwent chemical testing and other examination to determine age.
As far as Frumkin or other experts such as Shanks and Zuckerman could determine, the tests marked the first time that a well-identified biblical structure had been subjected to extensive radiocarbon dating.
Biblical accounts mentioned in Kings and Chronicles say the 1,750-foot-long tunnel was constructed to move water from the Gihon spring all the way across the ancient city of Jerusalem into the pool of Siloam to protect the city’s water supply from an Assyrian siege. The Assyrian empire was consolidating its control of the area after a rebellion led in part by Hezekiah.
The serpentine tunnel, now a tourist attraction, still bears pick marks from workers who occasionally had to adjust their course to meet with a second team of workers coming from the opposite side of the city.
The frequent direction changes suggest it was a struggle to connect the two ends of the tunnel without following the natural fissures and openings in the rock, Shanks said.
“The tunnel is extraordinary, but these guys didn’t know where they were going a lot of the time,” Shanks said.