A team of scientists from the U.S. Geological Survey’s Cascades Volcano Observatory have gone to Mexico to study the 17,887-foot Popocatepetl volcano, which began erupting Dec. 21.

At least 20,000 people were evacuated last week from the area around the mountain, located about 40 miles southeast of Mexico City.

Geologists Daniel Dzurisin and John W. Ewert and geophysicist Thomas Murray, all based in Vancouver, Wash., are teaming up with seismologist Randall A. White of Geological Survey’s office in Menlo Park, Calif.

White went to Mexico last week to set up seismicmonitoring equipment.

Popocatepetl, nicknamed “Popo,” is similar to volcanoes in the Cascade Range, and has experienced at least once catastrophic landslide similar to the one that devastated Mount St. Helens 14 years ago.

Popocatepetl, which means “smoking mountain” in Aztec, has erupted more than 30 times in recorded history. It was last active in the 1920s, when a series of small eruptions occurred for about five years. Early in 1994, earthquakes and gas emissions were recorded.

On Dec. 21, the volcano finally erupted, spewing thick plumes of ash and gas.

More than 30 million people live within sight of the volcano, which rises from a high plateau, and tens of thousands of people would be endangered by an explosive eruption.

The team of U.S. scientists is part of the Volcano Disaster Assistance program, funded by the Geological Survey and the Office of U.S. Foreign Disaster Assistance.

“We’re not only going to Mexico to help our Mexican colleagues, we are also going there to learn more about how this type of volcano works,” said program director C. Dan Miller.

Dzurisin said the team will be in Mexico for about two weeks.