lava dome

/L AA1 V AH0 D OW0 M/
noun
  1. 1

    A roughly circular mound-shaped bulge that builds up from the slow eruption of viscous felsic lava from a volcano.

    โ€œLava domes are rarely seen in shield volcanos.โ€

Source: https://en.wiktionary.org/wiki/lava%20dome