Excellent programme on BBC2 last night, the 15th of October, on the discovery of Heracleion in the delta zone of Egypt, at the head of the Canopic branch. Lots of collapsed Greek style temples and Egyptian inscriptions etc. After an hour we learned that it was an earthquake that may caused the sand and silt of the delta to collapse like quicksand. Other sources on the internet appear to suggest the sheer weight of stone monuments was part of the process – gradually sinking into the soft Nile delta soil. On Wikipedia we have the collapse of Heracleion dated as early as the second or third century BC. Other sources seem to think the city went out of service around 100BC. Still further sources claim it was finally submerged as late are AD800. The difference between the two extremes may be due to an assumption of a sudden and dramatic collapse of the city, on the one hand, and a prolonged submergence as a result of gradual liquefaction and gradual sea level increases. From the programme there appeared to be a lot of monuments and finds from between the 8th century BC and the 2nd century BC. Did the ruins poke out above sea level for another thousand years (or nearly so)? Was the demise sudden and dramatic?
Peter Fairlie-Clarke did a re-run of the programme and pointed out that a statue of Ptolemy VIII was discovered in the submerged city, and ceramics on one of the skuttled ships are dated to late 2nd/ eary 1st century BC. Hence, the earthquake must have occurred somewhat later.