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Volcanic cones are among the simplest volcano formations. They
are built by fragments (called ejecta) thrown up (ejected) from a volcanic 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.
- A spatter cone is formed of spatter: molten lava ejected from a vent. Expanding gases in the lava
fountains tear the liquid rock into irregular gobs that fall back to earth, forming a heap around the vent. The still partly
liquid rock splashed down and over the sides of the developing mound is called spatter. Because spatter is not fully
solid when it lands, the individual deposits are very irregular in shape and weld together as they cool, and in this way
particularly differ from cinder and ash. Spatter cones are typical of volcanoes with highly fluid magma, such as those found in
the Hawaiian Islands.
- 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.
- An example of a tuff cone is Diamond Head at
Waikīkī in Hawai'i.
- 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 300-500 m or so above their surroundings, and, being unconsolidated, tend to erode rapidly unless further eruptions occur.
Cinder cones are numerous in western North America as well as throughout other volcanic terrains of the world.
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