Popocatepetl volcano

The snow-covered Popocatepetl volcano spews a cloud of steam high into the air in Puebla...The snow-covered Popocatepetl volcano spews a cloud of steam high into the air in Puebla July 7, 2013. Mexican authorities raised the alert level for the Popocatepetl volcano on Saturday after an increased level of explosive activity belched ash over Mexico City and pushed international airlines to suspend flights.The alert level for the towering Popocatepetl volcano, located some 50 miles (80 km) to the southeast of the capital, was raised to yellow phase three from yellow phase two, Mexico's National Center for Disaster Prevention said in a statement. REUTERS/Imelda Medina (MEXICO - Tags: ENVIRONMENT TPX IMAGES OF THE DAY)

Imelda Medina/Reuters

The snow covered Popocatepetl volcano spews a cloud of steam high into the air in Puebla, Mexico, on Sunday. Mexican authorities raised the alert level for the Popocatepetl volcano on Saturday after an increased amount of explosive activity belched ash over Mexico City and pushed international airlines to suspend flights. The alert level for the towering Popocatepetl volcano, which is 50 miles (80km) to the southeast of the capital, was raised to yellow phase three from yellow phase two, Mexico’s National Center for Disaster Prevention said 

A cloud of ash belches out of Mexico's P...A cloud of ash belches out of Mexico's Popocatepetl volcano, some 55 km from Mexico City, as seen from Paso de Cortes, in the Mexican central state of Puebla, on May 20, 2013. Authorities have raised the alert level to "Yellow Phase Three," the fifth of a seven-stage warning system, restricting access to an area of 12 km around the volcano while preparing evacuation routes and shelters. AFP PHOTO/Arturo AndradeARTURO ANDRADE/AFP/Getty Images

Arturo Andrade/AFP

A cloud of ash belches out of Mexico’s Popocatepetl volcano, about 55km from Mexico City, as seen from Paso de Cortes, in the Mexican central state of Puebla. Authorities have raised the alert level to “yellow phase three”, the fifth of a seven-stage warning system, restricting access to an area of 12km around the volcano while preparing evacuation routes and shelters.