Watch Out

Shanghai (more than 18 million)

The first major world city to sink under its own weight could be Shanghai. Each year it sinks around 1 centimetre (half an inch) from subsidence after too much water extraction from the ground, and from the sheer weight of skycrapers on the soft ground it is built on.

As it sinks, the city faces a growing danger of floods from the River Yangtze. In 1911 the river flooded, drowning 100,000 people across four provinces, including Shanghai. The city’s subsidence also makes it more likely to flood from typhoons that strike regularly; and with rising sea levels that risk grows even worse.

Naples (At least three million live in the shadow of Vesuvius)

The volcano last erupted in 1944 and vulcanologists report that Vesuvius is in a 50-year cycle between eruptions, so it is overdue another explosion.

Its most famous eruption destroyed Pompeii in AD79, but long before that an even greater one destroyed the land on which Naples now lies and turned it into a wasteland.

There is a high chance of another violent eruption, with possibilities of avalanches of gas and ash, or flows of lava and mud. Lava and mudflows killed 18,000 people in 1631.

Vesuvius also sets off earthquakes, and in 1456 a quake killed 35,000 people and left Naples in ruins. The city’s buildings are largely poorly built, and a big earthquake or eruption coud leave it in ruins.

. . . and some that disappeared

Dunwich, Suffolk

An important medieval port, it collapsed into the sea from storms over a few hundred years

Tikal, Guatemala

Ancient Mayan city abandoned because of drought about 1,000 years ago

Pompeii, Italy

Destroyed by Vesuvius 79AD in an eruption that suffocated the population and buried the town in pumice and ash

Crete

The Minoan civilisation was wiped out on Crete about 3,500 years ago by a possible tsunami some 15m (50ft) high after the volcanic eruption of Thera, now known as Santorini

Canopus and Herakleion

Two Ancient Egyptian cities at the mouth of the Nile built on sediment that collapsed into the sea, possibly caused by huge Nile floods

Paul Simons writes the Weather Eye column in The Times

Times Recommends

• Darling won't pay for Brown give-away
• Believe it or not, Big Brother is your friend
• E-mails were quoted out of context