YELLOWSTONE NATIONAL PARK, Wyo. -- Sixteen small earthquakes with magnitudes up to 2.7 shook the park's Pitchstone Plateau last week.

The quakes were detected by seismographs operated by the University of Utah and partners.

They began Monday, just before midnight. The largest occurred at 3:09 a.m. Tuesday and the quakes continued until Wednesday, according to Bob Smith, a University of Utah professor.

"I was up working and watching these, saying 'Whoa, what does this all meanfi' " he said. "It kept my interest quite high."

The quakes occurred on the southern edge of a volcano caldera at the center of Yellowstone. The volcano last erupted 70,000 years ago.

Smith said earthquake swarms are common in Yellowstone. As many as 70 swarms of small earthquakes have occurred in the region between 1983 and 2006.

Probably no one felt the most recent quakes, Smith said.

This story appeared in The Daily Herald on page D3.