
A plume of smoke emanates from the crater of the Popocatepetl volcano in the state of Puebla, Mexico, on July 28, 2015. (Xinhua/Carlos Pacheco/NOTIMEX)

A plume of smoke emanates from the crater of the Popocatepetl volcano in the state of Puebla, Mexico, on July 28, 2015. (Xinhua/Carlos Pacheco/NOTIMEX)