Mexican authorities were on maximum alert Tuesday afternoon as el Popo began to show signs of a possible serious eruption, and a glacier at the summit was endangered by rising surface temperatures. Red-hot rocks the size of beach balls were exploding out of the crater.

Authorities have closed off a 10-kilometer ring around the volcano, and 30,000 people had been evacuated by noon Tuesday. Residents are no longer resisting Federal efforts at evacuation. When President Vincente Fox visited the area by helicopter, he was besieged by locals who told him that the recent upsurge in activity has frightened them badly. Nobody can remember a time when the volcano was this violent.

Through the night, Popo created a spectacular light show above Mexico City.

The Popo glacier is another concern. It is a hundred acres square and 65 feet deep, the size of a small lake. If it should melt, a torrent of water and mud would pour down into populated areas below. People living near the glacier have been evacuated and the army is patrolling towns in the path of possible melt.

Nearly all residents within seven miles of the volcano have been evacuated, and authorities on Wednesday morning were beginning evacuation of those within 12 miles. Mexico City is 30 miles from the volcano, and would be threatened only in the case of a tremendous eruption.

There was a significant eruption at 2AM Tuesday and another at 6AM, and volcanologists are not ruling out an eruption as powerful as the one 800 years ago, that spread lava over a wide area, and buried the entire region in ash. However, this is considered unlikely if Popo continues releasing energy in a series of smaller eruptions. The danger is if lava tubes within the volcano become clogged and the eruptions are replaced by earthquakes, indicating a build-up of internal pressure.

Precautionary flight cancellations have taken place in the area due to the danger airborne ash poses to jet engines and cockpit glass, which can be ‘sanded’ until it is opaque if a plane gets caught in an ash cloud.

US volcano experts are praising the high degree of professionalism being displayed by their Mexican colleagues, who have provided an exceptionally high level of monitoring expertise during the crisis. “This is the best-monitored volcano in the Western Hemisphere,” said Randall White of the US Geological Survey in Menlo Park, California.

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