High Quality Content by WIKIPEDIA articles! The 2004–2008 volcanic activity of Mount St. Helens has been documented as a continuous eruption with a gradual extrusion of magma at the Mount St. Helens volcano in Washington, United States. Starting in October 2004 and ceasing in January 2008, there was a gradual building of a new lava dome. The new dome did not rise above the caldera created by the 1980 eruption of Mount St. Helens.