Data from deformation-monitoring instruments indicated that during 5-11 December lava-dome growth at Mount St. Helens continued. Based on interpretations of flow-monitoring system data, lahars flowed out of the crater on 4 December, after a weather system passed through the region. Seismicity persisted at low levels, punctuated by M 1.5-2.5, and occasionally larger, earthquakes. Clouds occasionally inhibited visual observations.
Source: Cascades Volcano Observatory – “Reports provided courtesy of the Smithsonian’s Global Volcanism Program and the US Geological Survey’s Volcano Hazards Program.”