Tuff is a volcanic rock made of ash that was released in an explosive eruption and has lithified over time. Loose, unconsolidated debris is distinguished as tephra. Tuff are usually more thicker when they are around any volcano and less thick if it is more farther away from volcano. Tuff is used to describe a broad range of materials. The only requirement for any rock to be classifed as a tuff if it has air fall material from volcanic eprutions. The size of tuff rocks range from small to large.