Ash may be present in relatively minor amounts. The tephra accumulates near the central vent and builds a cinder cone. Magma associated with Strombolian activity is basaltic or andesitic and has a higher viscosity than Hawaiian magmas. Because of the higher viscosity, gas has greater difficulty escaping. Gas bubbles burst at the top of the magma column, producing small explosions and throwing clots of molten lava into the air.
Strombolian eruptions can last from a few hours or days to a few months or a few years.
The long duration of Strombolian activity is a common characteristic. Paricutin volcano in Mexico erupted continuously from 1943 to 1952, producing a cone made of cinder, bombs, lapilli, and ash. Izalco , in El Salvador, was constructed by Strombolian eruptions. Vulcanian eruptions are named after the cone of Vulcano in the Lipari Islands west of Italy. The eruption cloud can be gray or black.