A cinder cone or scoria cone is a steep conical hill of volcanic fragments that accumulate around and downwind from a volcanic vent.[1] The rock fragments, often called cinders or scoria, are glassy and contain numerous gas bubbles "frozen" into place as magma exploded into the air and then cooled quickly.[1] Cinder cones range in size from tens to hundreds of meters tall.[1] Cinder cones are made of pyroclastic material.
Many cinder cones have a bowl-shaped crater at the summit. Lava flows are usually erupted by cinder cones, either through a breach on one side of the crater or from a vent located on a flank.[1] If the crater is fully breached, the remaining walls form an amphitheatre or horseshoe shape around the vent. Lava rarely issues from the top (except as a fountain) because the loose, uncemented cinders are too weak to support the pressure exerted by molten rock as it rises toward the surface through the central vent.[1]
Sunset Crater, a typical cinder cone with little vegetation.
Cinder cones are commonly found on the flanks of shield volcanoes, stratovolcanoes, and calderas.[1] For example, geologists have identified nearly 100 cinder cones on the flanks of Mauna Kea, a shield volcano located on the Island of Hawaii.[1] These cones are also referred to as scoria cones and cinder and spatter cones.[1]