The story of Sodom and Gomorrah may have had more than a pinch of truth to it, new evidence reveals. The then-largest city in the region suffered a catastrophic collapse 3,600 years ago, and the cause appears to have been a nearby airburst from an asteroid or comet instead of war or famine. The impact apparently led to the entire lower Jordon valley being abandoned for 300-600 years and likely inspired the Biblical tale.
Tall el-Hammam, the rumored site of the Biblical Sodom, lies on the eastern side of the southern Jordan Valley. Archaeological evidence suggests that at its height it covered 66 hectares (165 acres) — 10 times larger than Jerusalem and five times Jericho.
Archaeologists have reveled in what Tall el-Hammam's layers tell us about thousands of years of habitation, but a catastrophe recorded around 3,600 years ago looks like nothing seen at any other ancient city. A paper in Scientific Reports makes the case the city was laid bare by an airburst similar to the Tunguska explosion.
Airbursts are huge explosions that occur in the air, possibly due to an object like an asteroid grazing Earth's atmosphere and bouncing out again without touching the ground. The Tunguska event of June 30, 1908 – when a massive explosion flattened 2,150 square kilometers (830 square miles) of Siberian forest – is believed to have released 30 megatons of energy, enough to level a city.
It's not hard to imagine how an event like that could morph into a Biblical story attributing a then inexplicable disaster to the wrath of God upon a sinful people.
When cities fall to earthquakes or invading armies it is common to find a layer of burnt items in the strata, but the researchers said this is very different. “We saw evidence for temperatures greater than 2,000 degrees Celsius (3,600 F),” Professor James Kennett of the University of California, Santa Barbara said in a statement. Examples included ceramics melted into glass and mudbricks heated so far they “bubbled”.
Even today, temperatures like that are hard to produce. The area lacks volcanoes that might have been the closest Bronze Age cause for such heat.
There is a heated debate about whether an asteroid impact or airburst 12,800 years ago triggered the Younger Dryas cooling event. Kennett is a leading advocate of the theory, and has been compiling evidence for the case. He wondered whether signs pointing towards a smaller, more recent, cosmic explosion could explain Tall el-Hammam's demise.
“I think one of the main discoveries is shocked quartz,” Kennett said. “These are sand grains containing cracks that form only under very high pressure...quartz is one of the hardest minerals; it's very hard to shock.”
The paper's authors also claim to have found iron-and silica-rich spherules associated with asteroid impacts in the soil at the relevant layer. On the southwest side, facing the Dead Sea, walls are sheared clean off, indicating the explosion came from that direction.
Nearby cities would not have experienced the direct effects Tall el-Hammam did, but Kennett's explanation for their abandonment has a particularly Biblical ring. Tall el-Hammam's destruction layer contains up to 25 percent salt in some samples and 4 percent on average. Centuries later the Romans sowed their enemies' fields with salt because it made farming impossible for generations and the dosage at Tall el-Hammam is much higher.
“The salt was thrown up due to the high impact pressures,” Kennett said. Although, as at Tunguska, the main asteroid would have exploded in the atmosphere, the Bronze Age impactor was probably larger, allowing some fragments to reach the ground. Any that hit the Dead Sea, or its salt-laden northern shores, would have thrown salt high into the air to be distributed across the region, affecting farming capacity around nearby settlements that escaped the direct blast.