Unwelded ignimbrite, Argentina -- This photo is a typical example of an unwelded ignimbrite. It consists of fist-sized dacitic pumice fragments and small, sparse lithic fragments in a fine-grained matrix of dacitic lapillia and ash. This example is from the 4.6 million year old Real Grande ignimbrite which has a volume of over 55 km3. Courtesy of Peter Francis.

To examine these unwelded ignimibrites on a microscopic scale, click on ignimbrite textures.