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 Mavna Loa in Hawaii is a shield volcano. Thousands of separate, overlapping lava flows, each less than 50 feet thick, formed Mavna Loa.
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. When the eruptions ended in 1952, the top of the cone was 1,345 feet above its base. Composite volcanoes are formed when both lava and tephra erupt from a central vent.