MEXICO CITY — Popocatépetl, the active volcano that rises some 40 miles southeast of the Mexican capital, exploded Monday night, sending a plume of ash and gas more than two miles into the inky sky and raining glowing rocks onto its slopes.
Video released by Mexico’s national disaster prevention agency showed a fiery light at the volcano’s crater at 9:38 p.m. The explosion was quickly enveloped in ash and pulverized rock as burning fragments of the volcano’s dome fell over a radius of a mile and a half.
Popocatépetl, whose name means “smoking mountain” in Nahuatl, the language of the Aztecs, sprang back to life in 1994 after a half-century of quiescence. Since then, the residents of the surrounding towns have grown accustomed to frequent emissions of gas and ash and periodic eruptions.
Over the past few weeks, the volcano has become more active, prompting the authorities to repeat warnings to keep a distance of about seven miles away from the summit.
Though the images were eye-catching, Ana Lillian Martín del Pozzo, a volcanologist at the Geophysics Institute of the National Autonomous University of Mexico, said that previous explosions have been larger.
Several factors combined to produce the pictures that sped across social media — beginning with the fact that the explosion occurred at night. And the volcano is monitored by more cameras than in the past. “It’s very impressive at night when it’s lit up,” Dr. Martín said.
In addition, the crater has gradually been building up since activity restarted in 1994, so the explosions are more visible, occurring just 150 feet from the edge.
“We do know that there is magma in the upper part of the crater that hasn’t come out yet,” Dr. Martín said. “Activity is ongoing. The main thing is stay away from the 12-kilometer exclusion zone,” which is the radius over which rocks have fallen in earlier, more powerful explosions.
Popocatépetl, which is a complex newer volcano over several older volcanoes, has historically produced large eruptions every 500 to 1,000 years, Dr. Martín said. An eruption in the 1660s plunged the city of Puebla into darkness for three days as ash filled the sky.
Since the volcano’s activity resumed in 1994, several medium-size eruptions have sent ash as far as Mexico City and created plumes almost four miles high. An explosion in 1996 killed five mountain climbers.
“People should not go up,” Dr. Martín said. “It’s not exciting — it’s silly.”