An aerial view of Popocatepetl volcano spewing a column of smoke and ash 4,921 ft (1500 meters) high into the sky, in the outskirts of Puebla is seen in this June 25, 2013 picture provided by Mexico's National Disaster Prevention Center (CENAPRED) made available to Reuters on June 26, 2013. The 5,450-meter (17,900 ft) Popocatepetl volcano has been kept on yellow phase two alert, the second-highest warning on the center's seven-step scale, Mexico's National Center for Disaster Prevention reported. Picture taken June 25, 2013.[Photo/Agencies]