Most cinders fell very near the central vent, building a small cone. Cinder by cinder Layer upon layer of volcanic ejecta are laid down, building a higher and steeper cinder cone. Eventually the cone gets so steep that the sides collapse under their own weight. The collapsing cinders come to rest when they reach just the right steepness to keep them stable. Every pile of loose particles has a unique angle of repose, depending upon the material it's made from.
Cinder cones can grow very large, even wider in diameter than their maximum ejection distance.
As cinders continue to pile high near the central crater, they will continually collapse. Eventually the collapsing sides can spread a considerable distance beyond the 'throwing distance' of the cone-but they always maintain the same straight sides at just the right shape. This site is a cooperative endeavor of the US Geological Survey Western Earth Surface Processes Team and the National Park Service .