Volcanic cone

Volcanic cones are among the simplest volcano formations. They are built by fragments erupted from a vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and size of the fragments ejected during the eruption. Types typically differentiated are spatter cone, cinder cone, ash cone, and tuff cone.

• An ash cone is comprised of particles of silt to sand size. Explosive eruptions from a vent where the magma is interacting with groundwater or the sea (as in an eruption off the coast) produce steam and are called phreatic. The interaction between the magma, expanding steam, and volcanic gases results in the ejection of mostly small particles called ash. Fallen ash has the consistency of flour. The unconsolidated ash forms an ash cone which becomes a tuff cone (see tuff) once the ash consolidates.

• A cinder cone is a volcanic cone built almost entirely of loose volcanic fragments called cinders (pumice, (pyroclastics, or tephra). They are built from particles and blobs of congealed lava ejected from a single vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone. Most cinder cones have a bowl-shaped crater at the summit. Cinder cones rarely rise more than a thousand feet or so above their surroundings. Cinder cones are numerous in western North America as well as throughout other volcanic terrains of the world.