Most of the scoria falls to the ground near the vent to build up a cone-shaped hill called a “cinder cone.” Cinder cones are generally small volcanoes produced by brief eruptions with a total vertical relief of less than a few thousand feet. They are usually very steep because scoria has an angle of repose of 30 to 40 degrees.

In some parts of the world, cinder cones occur in clusters of a few to hundreds of individual cones. These areas are called “volcano fields.” An example of a volcano field is the San Francisco Peaks Volcanic Field near Flagstaff, Arizona, which contains over 500 cinder cones.