Cinder cone, or scoria cone, volcanoes are cone-shaped hills that form when lava fragments are ejected from localized vents and pile up and solidify around the opening. Cinder cones can be standalone formations or develop on the slopes of shield volcanoes and stratovolcanoes. Mount Etna in Sicily and Mauna Kea in Hawaii are well-known volcanoes with hundreds of cinder cone formations along their sides.
Scoria is a type of volcanic basalt rock around a cinder cone crater. As trapped gases increase heat and pressure inside volcanoes, fountains of magma form and flow out of the vent openings. The lava cools and turns into hardened fragments as it explodes out into the open air, gradually forming the sides of the vent into a layered crater. Volcanic activity that produces a cinder cone is known as a Strombolian eruption.
Cinder cones are the smallest volcanoes, reaching an average height of 300 feet and a maximum height of roughly 1,200 feet, according to LiveScience. In general, these formations start off with a round shape, but violent eruptions or persistent wind can shift the vent location or lava flow. New cinder cones can form in months or years, making them the most common form of volcano.