Noun
lava dome (plural lava domes)
(volcanology) A roughly circular mound-shaped bulge that builds up from the slow eruption of viscous felsic lava from a volcano.
Lava domes are rarely seen in shield volcanos.
Mount St. Helens has been building a new lava dome since the May, 1980 eruption.
Lava dome growth profile from 1980–1986 By about 5:30 p.m. on May 18, the vertical ash column declined in stature, and less severe outbursts continued through the night and for the next several days. Source: Internet