04:26 PM PDT on Wednesday, May 31, 2006

By FRANK MUNGEAM, kgw.com Staff

VANCOUVER, Wash. -- A minor earthquake occurred at 9:08 a.m. Monday, eight miles southwest of Mount St. Helens. The magnitude 3.1 event was centered 2 miles underground.

USGS

A plume of ash rises from Mount St. Helens on Memorial Day.

The quake was accompanied by a volcanic ash plume that rose to 16,000-20,000 feet, according to airline pilots in the area.

It was a very weak plume with little ash, according to Carolyn Drieger with the USGS. Six minutes later it was just white steam.

Watch SLIDE SHOW of ash plume

USGS geologists say they saw ash over crater floor, using remote cameras, and it appeared that some parts of the new dome and fin have collapsed.

USGS

The fin in the crater of Mount St. Helens, covered with ash from the Memorial Day event.

It was not initially clear whether the quake caused the collapse or the collapse caused the quake.

Geologists at the U.S. Geological Survey report a slight increase in the size and frequency of earthquakes at the mountain over the past few weeks but say the increased activity is not out of normal for the mountain's range of activity in the past year.

Dome building in the crater of Mount St. Helens has been taking place since September of 2004 and a large fin has grown, then fractured, and begun to grow again in the past month.

Read USGS on site report on latest Mount St. Helens seismic activity