According to paleomagnetic studies, the volcano is about 730,000 years old. It is cone shaped with a diameter of at its base, with a peak elevation of . The crater is elliptical with an orientation northeast-southwest. The walls of the crater vary from in height. Popocatépetl is currently active after being dormant for about half of last century. Its activity increased in 1991 and smoke has been seen constantly emanating from the crater since 1993. The volcano is monitored by the Deep Earth Carbon Degassing Project.