pyroclastic shield volcano A shield volcano that is formed mostly of pyroclastic and highly explosive eruptions rather than relatively fluid basaltic lava issuing from vents or fissures on the surface of the volcano. They typically display low-angle flank slopes and have little or no central collapse, although a shallow sag in the shield is commonly observed. Lava is commonly extruded after the cessation of explosive activity commonly superposes the vent region. ENVO ENVO:00000372 terrestrial ignimbrite shield ignimbrite shield volcano shield volcano