Popocatépetl volcano spews smoke and ash, putting millions of Mexicans on alert

Popocatépetl volcano spews incandescent material on Tuesday. The second highest volcano in the Mexico increased its activity, and authorities raised the alert to the second-highest level. (Cristopher Rogel Blanquet/Getty Images)

Popocatépetl volcano just outside Mexico City has been erupting occasionally since 1994, but over the past week it has rumbled every day.

Scientists have recorded hundreds of explosions, and webcams trained on the volcano have shown it spewing incandescent material. From Mexico City, you can see a column of ash rising from the summit.