The most common types of volcanoes are the cinder cone volcanoes. Cinder cone volcanoes are steep sided cones composed of fragments of basalt. Unlike shield volcanoes or stratovolcanoes, the cinder cone volcano contains only one vent, its central vent. Ash, bombs, and cinders pile around a vent and form a circular or oval cone when a cinder cone volcano is created. (Cinders are cooled volcanic rock that formed pebble-sized pieces when it was thrown out above the surface. Bombs in volcanic terms are magma that was shot out into the air and hardened into rock before it hit the ground) Cinder cones can either be found standing alone, or in groups both small and large. Strombolian eruption cause cinder cones to be formed. The cone of the volcano's height depends on how long the eruption lasted.