Volcanic cones are generally made by pyroclastic activity, where molten material explodes out of the ground and falls back onto the surface as small bits of glassy rock called ash. This ash piles up around the vent, creating a cone shape, usually with a volcanic crater in the middle.
Volcanic cones that have alternating layers of ash and lava make large stratovolcanoes.
Sometimes lava pours out of the volcano in between pyroclastic episodes, cementing the ash in place. This layering allows large, mountain-sized stratovolcanoes, or composite volcanoes, to form. Smaller cinder cones may form on the flanks of such volcanoes.
Examples of stratovolcanoes on the planets