Composite volcanoes are made of a variety of materials.
A hardened piece of magma may plug up the vent and be blown out by the built-up gases below.
Fragments of ash and cinder shoot into the air accompanied by lava that flows down the slopes. The cone, therefore, will have alternating layers of ash, cinder, and lava, as each falls and hardens on top of the other.
Composite volcanoes tend to have dramatic, steep summits sloping down to wide, softer-looking bases of hardened lava.