Mt. Helen is a dacitic lava dome (~249 ka.) in the Lassen volcanic center; a long-lived (~600ka. - present), silicic volcanic center superimposed on regional mafic magmatism in the southernmost Cascade volcanic arc.
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Mt. Helen is a dacitic lava dome (~249 ka.) in the Lassen volcanic center; a long-lived (~600ka. - present), silicic volcanic center superimposed on regional mafic magmatism in the southernmost Cascade volcanic arc.