A tuff ring or tuff cone is a wide, low-rimmed, well-bedded accumulation of debris built around a volcanic vent located in a lake, coastal zone, marsh or an area of abundant groundwater. A tuff cone is merely a taller variant of a tuff ring, they are both formed by phreatomagmatic eruptions. Tuff itself is an igneous rock formed by the airfall of volcanic ash or pumice. Tuff rings are usually fed by volcanic pipe. [ - ]

A tuff ring or tuff cone is a wide, low-rimmed, well-bedded accumulation of debris built around... [ + ]