Cliffs of ash flow tuff, ColoradoDecember 31, 2017/in /by Marli Miller pyroclastic, ignimbrite, volcanic https://geologypics.com/wp-content/uploads/2017/04/geologic-time-pics-logo-300x115.png 0 0 Marli Miller https://geologypics.com/wp-content/uploads/2017/04/geologic-time-pics-logo-300x115.png Marli Miller2017-12-31 11:39:272017-12-31 11:48:14Cliffs of ash flow tuff, Colorado