<p>A cinder cone or scoria cone is a steep conical hill of tephra (volcanic debris) that accumulates around and downwind from a volcanic vent. They consist of loose pyroclastic debris formed by explosive eruptions or lava fountains from a single, typically cylindrical, vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as either cinders, clinkers, or scoria around the vent to form a cone that often is beautifully symmetrical; with slopes between 30-40°; and a nearly circular ground plan. Most cinder cones have a bowl-shaped crater at the summit.
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<a rel="nofollow" class="external text" href="https://www.flickr.com/people/75683070@N00">Ken Lund</a> from Reno, Nevada, USA
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/kenlund/16260709162/">Cinder Cones Near Concho, Arizona</a>