Radioactive dating of material inside an ancient water tunnel beneath Jerusalem appears to confirm it was dug some 2,700 years ago to thwart an Assyrian siege as described in the Old Testament.
The 1,750-foot passage winds beneath old city walls to bring water within the defensive perimeter from the only year-round spring in the area, Gihon, to a pool called Siloam.
The books of Kings and Chronicles mention that King Hezekiah ordered the diversion of the spring both to supply the city and to deny the water to an invading force led by Assyrian King Sennacherib, moving to lay siege to Jerusalem in 701 B.C.
Biblical scholars have debated, though, whether the tunnel had actually been dug five centuries later.
An inscription found at one end of the tunnel in 1880 described how "hewers" with axes worked from both sides of a hill and finally linked up by calling to one another but gave no date for the work. Scientific dating of the inscription based on weathering of the rock suggested a date of around 700 B.C. but could have been hundreds of years off.
Researchers, led by Amos Frumpkin of Hebrew University in Jerusalem, used two types of radiometric dating on plaster covering the tunnel walls and floor, and on tunnel stalactites.The scientists' findings about the passageway's time of origin, taken with historical records, "all converge on about 700 B.C., rendering the Siloam Tunnel the best dated Iron Age biblical structure thus far known," Frumpkin said. "We believe this point is now clearly settled."
Getting accurate dates for specific biblical structures is difficult. Most sites are either not clearly identified, have been poorly preserved or looted, or are off-limits to scientists because of religious or political significance.
Many scholars have argued that Hezekiah's tunnel, built at the supposed urging of the Prophet Isaiah, was both a technological marvel for its time and a turning point in Jewish history by allowing Jerusalem to survive as the center of a revitalized Judaism.
For thousands of years before and after Hezekiah, most tunnels were dug by digging vertical shafts at intervals, then cutting horizontal passages to connect them. But the Siloam Tunnel only broke the surface at each end, and is hundreds of feet below the surface in many spots.
It would have been shorter by 40 percent had Judean engineers followed a straight line. But modern geologists suspect that digging crews actually followed limestone deposits or water seeping through the rock to complete the project as soon as possible, in a matter of months.
The Bible and Assyrian chronicles report that the siege failed, although the exact reasons remain uncertain. The Old Testament mentions both that Hezekiah paid the Assyrians tribute to leave and that an avenging angel destroyed much of the invading army. Assyrian tablets also mention tribute, but suggest that military pressure from enemies in Egypt or back in Mesopotamia might have forced the withdrawal from Judea.
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