Popocatepetl rumbled for 4 minutes on Saturday, then spewed ash on nearby communities. Residents had all returned home after being evacuated on December 18, when showers of red-hot rock began shooting out of the volcano. This was its biggest eruption in 1,200 years.
Scientists say that the volcano is trying to dislodge a mass of lava that is stuck deep in its crater. They expect it to continue erupting for several weeks. The ash could further pollute the air in Mexico City, which already has one of the worst air quality levels in the world, and even effect the southwest United States. It could also contaminate the underground water supply of one of the world?s largest cities.
Popo's future actions cannot be predicted. It is possible that the volcano will slowly vent steam and debris until its present activity phase ends. However, if the millions of tons of lava now near the surface cannot be expelled, there is danger that the volcano will explode like Mt. St. Helens. Such an event would place one of the world's most densely populated areas at serious risk.
A foot or more of ash might fall on Mexico City, clogging roads, causing roofs to collapse and damaging power lines. Worse, it would clog water pipes and bring the city's already fragile water distribution system to a halt, possibly for an extended period. Even though the city would be unlikely to suffer from lava flows or flying boulders, this would be one of the most serious crises ever faced by a major metropolitan area.
The aerosol from such an event would reach far into the upper atmosphere, and would significantly reduce the amount of sunlight reaching earth, causing alterations in climate, possibly a period of cooling.
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