Cinder cone

A cinder cone is a steep, conical hill of volcanic fragments that accumulate around and downwind from a vent. 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. Cinder cones range in size from tens to hundreds of meters in height.

Facts and figures: Perhaps the most famous cinder cone, Paricutin, grew out of a corn field in Mexico in 1943 from a new vent. Eruptions continued for 9 years, built the cone to a height of 424 meters, and produced lava flows that covered 25 km square kilometers.

Cinder cones are commonly found on the flanks of shield volcanoes, stratovolcanoes, and calderas. For example, there are dozens of cinder cones on the flanks of Mount Etna. They have formed during lateral eruptions which have often threatened and damaged towns on the lower slopes of the volcano.

Cinder cones on the summit of Mauna Kea, Hawaii, are used as foundations for some of the world's largest astronomical telescopes.

Monti Silvestri cinder cones, Mt. Etna (erupted 1892). Photo: J. Alean