ash cone

cinder cone

 or ash cone

Deposit around a volcanic vent, formed by rock fragments or cinders that accumulate and gradually build a conical hill with a bowl-shaped crater at the top. Cinder cones develop from explosive eruptions of lavas and are often found along the flanks of shield (gently sloping) volcanoes. Lava flows may break out of the cone, or they may flow from under the cone through tunnels. Cinder cones are common in nearly all volcanic areas. Although they are composed of loose or only moderately consolidated cinder, many are surprisingly long-lasting, because rain falling on them sinks into the highly permeable cinders instead of running off down their slopes and eroding them.

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ash cone [′ash ‚kōn]

(geology)

A volcanic cone built primarily of unconsolidated ash and generally shaped somewhat like a saucer, with a rim in the form of a wide circle and a broad central depression often nearly at the same elevation as the surrounding country.