First came waves of yellow ants and large, black centipedes. They scrabbled down the scrub-covered slopes of Martinique's Mount Pelée, scuttled over roads and tracks, and attacked workers in nearby cane fields. They even invaded the local landowner's house.

Then the snakes began their exodus. Hundreds, including deadly pit vipers, twisted and writhed down the volcano's flanks and headed across the countryside. It could have been a biblical plague.

Finally, at 8am on 8 May 1902, Mount Pelée blew its top, sending a massive cloud of incandescent gas hurtling down its flanks. Travelling at more than 100mph, it struck St Pierre at 8.02am.

Three minutes later, the 'Paris of the West Indies' lay in ruins, its 30,000 inhabitants suffocated and burnt. Only one person survived: Auguste Ciparis, the sole occupant of the city's dungeon.

The destruction of St Pierre was complete, and unprecedented. The cause, scientists now know, was a nuée ardente (glowing cloud) or pyroclastic flow - a mixture of gas, steam, glowing dust, ash and pumice. It was the first time such an event had been observed, however.

Since then scientists have learnt much about these deadly eruptions and have established how to predict volcanic behaviour with precision. Yet as researchers prepare to mark the centenary of history's worst volcanic disaster, many now fear that this knowledge could prove useless and that future eruptions could have even more devastating effects on humanity.

'There are more than 3,000 volcanoes in the world, and only about 150 are being monitored,' said Professor Bill McGuire, a volcanologist at University College London. 'There are also so many more people alive today and that makes us more, not less, vulnerable to eruptions in the twenty-first century.

'And although we can predict eruptions, we cannot force politicians to take action and be ready to implement expensive evacuation plans.

'For instance, around Vesuvius in Italy, a million people would be under threat the next time it erupts, so poor are local evacuation plans. Very few people seem to understand the danger we still face.'

Such complacency mir rors how local authorities ignored the dangers of Mount Pelée. Apart from visitations by escaping insects and snakes, major earth tremors and mud flows had killed several inhabitants by the end of April 1902.

Yet municipal leaders refused to act. The island was in the midst of general elections, with socialists poised to take control from right-wing politicians. However, St Pierre was the main centre of conservative votes, and so the governor, keen to keep his right-wing colleagues in power, put off evacuation until polling day on 11 May.

The horrific consequences of this delay were described by Charles Thompson, assistant purser of the steamship Roraima which was moored in St Pierre. 'The fire rolled down upon St Pierre,' he recalled. 'The town vanished before our eyes.'

Another ship, the Rod ham, managed to sail out of the harbour as pumice and ash rained on its deck. It headed for St Lucia, most of its crew dead or dying. The Rodham was met by stunned customs officials who asked the survivors of the scorched ship where it had come from. 'From the gates of hell,' came the captain's answer.

'Two other volcanic eruptions have had worse death tolls - Krakatoa in 1883, which killed 36,000, and Tambora, in 1815, which killed 92,000,' said McGuire, whose book, A Guide to the End of the World (OUP), has just been published.

'But many of these deaths were caused by secondary effects. Tambora destroyed rice fields throughout the Dutch East Indies and people starved to death, while Krakatoa triggered a tsunami, a massive tidal wave that led to the drowning of most of its victims. However, Mount Pelée was the direct cause of its victims' deaths.'

But the effects of Pelée's eruption went beyond killing people in its neighbourhood. Its impact is still felt today, as Jelle Zeilinga de Boer and Donald Theodore Sanders point out in Volcanoes in Human History (Princeton).

In 1902, the United States was preparing to fund a canal to connect the Pacific and Atlantic oceans, either through Panama or through Nicaragua.

Nicaragua was known for its volcanic activity and, after the destruction of St Pierre, the prospect of another major eruption damaging the canal was enough to persuade the US Senate to approve the Panama project by eight votes.

As for Auguste Ciparis, after surviving four days in his cell, which was buried beneath layers of ash, his sentence (for assault) was suspended and he spent the rest of his days touring with the Barnum and Bailey Circus - as an exhibit in a replica of his prison cell.

· Additional research by Hannah Richards