Is much of the Old Testament little more than fairy tale? Possibly so, but recent research has shown that the story of Sodom and Gomorrah vanishing from the face of the earth might just be true.

"Then the Lord said: The outcry against Sodom and Gomorrah is so great and their sin so grievous that I will go down and see what they have done... Then the Lord rained down burning sulphur on Sodom and Gomorrah... Thus he overthrew those cities and the entire plain, including all those living in the cities - and also the vegetation in the land." (Genesis, chapters 18 and 19) To believers, Sodom and Gomorrah were symbols of divine destruction so complete that not a trace of them remained. Modern archaeologists tend to believe that because nothing remains - no bones, no ruins, no reason for ancient people to build on the inhospitable shores of the Dead Sea - the biblical cities probably never existed, although recently, amateur archaeologist Michael Sanders claims to have located their foundations.

A retired civil engineer, a BBC documentary team and Cambridge University's earthquake centre recently joined forces to suggest why Sodom and Gomorrah could have existed before dramatically disappearing more than 4,000 years ago.

The story starts with engineer Graham Harris, who for ten years worked for a potash plant on the edge of the Dead Sea, testing soil structures and their suitability for building foundations. Harris, 64, began wondering about Sodom and Gomorrah years ago, after he heard an archaeologist deny their existence. He read the account in Genesis and concluded that the cities could have been destroyed in an earthquake.

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He knew the Dead Sea region was vulnerable to earthquakes. He also knew that its soil was prone to an earthquake-related phenomenon called liquefaction.

Liquefaction occurs when an earthquake hits loosely packed soil, such as sand and silt. The soil compacts downwards; the water normally held within the soil rises upwards; and solid ground turns instantly to a kind of soil soup. Buildings on liquefied land will quickly sink and crumble away.

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After Harris published his theory about Sodom and Gomorrah in the Journal of Engineering Geology , a BBC researcher contacted him and together they compiled a list of questions to be answered if they were to show that Sodom and Gomorrah might have existed. First they needed evidence of settlements by the Dead Sea during the period. Was there any logic as to why such settlements would have existed? Then they needed geological evidence for earthquakes during that period, for a soil structure prone to liquefaction and for the Bible's "burning sulphur".

Excavations in Jordan uncovered settlements between 2,800 and 2,300BC. Harris had argued that the ancient bitumen trade justified a Dead Sea settlement. Israeli scientists revealed evidence of an international bitumen trade from the Dead Sea by "fingerprinting" Dead Sea bitumen in ancient Egyptian remains. British geologists found evidence for liquefaction and traces of earthquakes in the local rock strata. And the fires? Jordanian engineers had stopped road-building near the Dead Sea in the 1980s when pockets of methane gas - biblical "burning sulphur"? - literally blew up in their faces.

The details were right, but the big question remained. How could an entire city disappear without trace and leave no archaeological record? To answer that, the BBC went to Cambridge's Schofield Centrifuge Centre.

People worried about earthquakes go to Cambridge to use the "Earthquake Actuator" - a box that generates, stores and expresses large amounts of mechanical energy, simulating the effect of an earthquake on whatever is spinning on the centre's centrifuge arm.

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The BBC asked the Schofield Centre's assistant director and earthquake engineering specialist Gopal Madabhushi to subject a model of Sodom and Gomorrah to a medium-sized earthquake. Madabhushi was intrigued. He made two predictions. One was that the clay-sand-clay sandwich beneath the hypothetical city would be astonishingly slippery after an earthquake, as the impermeable clay formed a cushion on top of the liquefied sand. The other was that a city built on a shoreline would be affected by the inevitable slope. In an earthquake, Sodom and Gomorrah would slide into the sea. Based on archaeologists' sketches, he built nine tiny Perspex and brass Bronze Age dwellings and put them on top of clay and water-holding sand in a flexible box that would mirror any distortion of the soil. The box went on the centrifuge, connected to instruments measuring the soil's acceleration and the water pressure under it. When it was spinning at 106 rotations per minute - about 250km/h - and subjected to a force of 50G, it experienced an earthquake measuring 6 on the Richter scale.

Although the houses sank and slid, the box sides prevented them from disappearing. In reality, says Madabhushi, even with only a 3-degree slope down to the water, the sea would have risen above the level of the land and swallowed them. The buildings would have slid for a kilometre or more, probably ending up on the flattest part of the sea bed. "The sea moves in and at the same time the houses are moving horizontally into the sea. If you just had an earthquake and liquefaction and houses slipping away, some people would have had time to get out. But when the sea moves in, we are looking at a few seconds after the earthquake. That is not long enough for anyone to escape."

The disaster would have been swift and absolute. No wonder that some distant onlooker or miraculous survivor turned it into a story of divine vengeance.

Ancient Apocalypse: Sodom and Gomorrah will be broadcast on BBC2, August 16, at 9pm.

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