lava dome

noun1

1. •
   A convex volcanic structure made of generally viscous, felsic lava, which grows slowly over time by extrusion from a volcanic edifice, either endogenously, by inflating from within, or exogenously, as erupted flow lobes of lava.

   • Lava domes are rarely seen in shield volcanos.
   • Mount St. Helens has been building a new lava dome since the May, 1980 eruption.