Triple volcano risk to 70,000
The most serious threat is posed by the Merapi volcano in central Java, one of the most dangerous volcanoes in the Pacific "Ring of Fire", which was yesterday throwing out ash and small rocks. Geologists believe that the 1.7-mile high volcano could violently erupt at any time.
Two other volcanoes also giving cause for concern are the Galeras volcano in Colombia - expected to erupt within a matter of days or weeks - and the Urbinas volcano in southern Peru, which also appears to be gearing up for an eruption.
Aid workers have voiced concerns about the threat posed to the thousands of people living in the vicinity of the volcanoes and the Foreign Office has issued a travel warning advising British citizens to avoid the area around Mount Merapi.
It said the Indonesian centre for vulcanology had raised the alert status for the volcano and warned that an eruption might be imminent.
It added: "Indonesian authorities have evacuated the villages closest to the volcano and some flights over the area have been cancelled."
Aid agencies are preparing for the worst. Oxfam has briefed staff that up to 60,000 people in four districts around Merapi are at risk and that several hundred have already been relocated.
Most of those relocated are women, children and the elderly, but some are returning to their homes near the volcano during the day to feed livestock.
Yesterday, the tower of sulphurous smoke over the volcano had risen to 1,640ft and a rain of ash fell on one village on its slopes, which overlook the ancient city of Yogyakarta.
The volcano has a history of violent eruptions. In 1994 it killed 70 people and a 1930 eruption cost the lives of 1,300 people.
Government officials, including Hamengkubuwono X, the sultan of Yogyakarta and provincial governor, have been urging residents to leave the foothills, saying Merapi could erupt any time. Local vulcanologists have also noted the magma inside the volcano is reaching its peak.
The Galeras volcano in Colombia began erupting in 1988 after a period of dormancy and it has a history of large-scale eruptions. About 7,000 people are thought to be at risk if, as expected, it erupts in the near future, and aid workers report that many of those directly at risk have not left their homes.
The potential eruption of the Urbinas volcano in southern Peru puts some 4,500 people at risk. The volcano, about 470 miles from Lima, has triggered earth tremors which have been felt in the capital.
Peruvian authorities have declared a state of emergency in the area after the volcano started to eject gas and ash over a radius of 3.5 miles. Geologists report a dome of lava appears to be building in the crater, a sign that an eruption is imminent.
The eruption of any volcano can have an effect on local and global climate and three large eruptions close together could have a significant impact, leading to cooler temperatures.
The eruption of Mount Pinatubo in 1991 led to a drop in global air temperature over the next three years of between 0.2 and 0.5 C, according to NASA, which conducted a study into the effects of the millions of tonnes of ash and sulphur dioxide blown into the atmosphere.
Yesterday David Crichton, visiting professor at the Benfield Hazard Research Centre at University College London, said it was possible that the three volcanoes now expected to erupt could have similar effects.
"Volcanoes can have an impact on climate," he said. "Sulphur dioxide can have a cooling effect and there is also a dimming effect on the sun caused by the clouds of ash."