This combination of gas and dust looks like black smoke. These groups are based on the shape of the volcanoes and the type of material they are built of. Shield volcanoes are formed when a large amount of free-flowing lava spills from a vent and spreads widely. The lava gradually builds up a low, broad, dome-shaped mountain. The famous Mauna Loa in Hawaii is a shield volcano.
Cinder cones build up when mostly tephra erupts from a vent and falls back to earth around the vent.
The accumulated tephra, which is generally cinders, forms a cone-shaped mountain. Paricutin in western Mexico is a well-known cinder cone. It began in 1943, when a crack opened in the ground of a cornfield. Composite volcanoes are formed when both lava and tephra erupt from a central vent. The materials pile up in alternate layers around the vent and form a towering, cone-shaped mountain.