Don't blame sneaky Greeks in a hollow horse for breaching ancient Troy's defenses. Don't look to besieging armies to explain Jericho's repeated destruction. Don't ask who buried some of the Dead Sea scrolls. Impersonal earthquakes - not human violence - may have done the job.
Geophysicist Amos Nur has taken a new look at ancient Eastern Mediterranean history. Where archaeologists see mainly the remains of warfare and pillage, he sees seismic destruction. He has also taken a new look at the region's seismicity.
According to conventional theory, quakes occur independently here and there along a fault line as accumulated strain is released in local areas. Instead, Dr. Nur sees evidence that devastating quakes can occur in swarms that can unzip an entire fault line. Swarms would be separated by long periods of quiescence.
This could lull inhabitants into a false sense of security. But when a swarm hits, cities built along the fault could be knocked out within decades.
Nur says that may be what ended the region's Bronze Age when dozens of civilized centers - including Knossos, Mycenae, and Troy - were destroyed within a 50-year period. If it happened then, it could happen now. That makes this new look at ancient history relevant to efforts to better understand earthquake hazards in regions like the Middle East, where large population centers now lie along or close to dangerous fault lines.
Nur, who is chairman of Stanford University's geophysics department in Stanford, Calif., explained this to reporters last month during the meeting of the American Geophysical Union in San Francisco. He noted that, while he feels confident of his ideas, they challenge long-held assumptions. He needs more research to back them up.
It can seem arbitrary, for example, to blame an earthquake for a city's destruction when there's evidence that a war was going on. In Nur's view, the quake opened up the defenses to attackers. He explained that the protected centers were strongholds of an elite that exploited the populace. "The earthquakes made these centers open to attack, mostly from the indigenous people," he said.
Even in Troy, where there was a besieging army, a quake seems to Nur to have been the likely agent in opening the city walls.
There's more direct evidence from other cities. Megiddo - the biblical Armageddon - commanded the Nahal Iron Pass through the Carmel-Gilboa mountains on the road from Egypt to Damascus. Armies devastated this key city more than once. It also lies near a branch of the Dead Sea fault system.
Nur thinks the armies may have had help from quakes. He noted there are three layers of destruction that warfare can't explain. "It is beyond doubt that Megiddo, along with its neighboring territories, must have experienced earthquakes strong enough to cause significant or total destruction," he said.
Such suspicions are buttressed by evidence of sudden collapse of massive structures. Human skeletons and their goods lie beneath rubble. Nur has found similar evidence of sudden collapse in a Dead Sea scroll cave where skeletons underlie rubble. "There was a huge earthquake around 21 BC" that could have collapsed the area, he said. This trapped the inhabitants who wrote the scrolls and buried the scrolls, Nur suggested.
Historians and archaeologists know that earthquakes have shaken the Eastern Mediterranean many times. However, Nur noted, these observers generally are unfamiliar with geophysics. "If you haven't taken Geology One," you don't know that quake damage can extend over hundreds of kilometers.
Furthermore, if geologists hadn't realized that quakes can occur in swarms along a fault, there was no reason to link the sequential destruction of cities along the fault to a major geophysical event.
Nur said he hopes to pin down his earthquake-swarm hypothesis so it can someday be useful in predicting periods when a susceptible fault system will be quiet and when it will be dangerous. That's a long-range goal. He noted that "right now, earthquake patterns aren't regular enough to tell us anything."
The seismic future
He added that getting data on the region's quake history will be difficult. That's where he hopes archaeology will help. Evidence of destruction with columns and walls falling in one direction, rather than every which way, probably is "as compelling evidence as you can get" of an ancient quake. With this in mind, archaeologists searching for clues to the past may also turn up clues to the region's seismic future.