Any type and size of rock fragment that is forcibly ejected from the volcano and travels an airborne path during an eruption (ash, bombs, scoria, cinders, etc.). Generally synonymous with fallout, but sometimes used more loosely to embrace pyroclastic-flow material as well.

Tephra - Basalt Boulders Petroglyph NM














Native Americans used tephra for various things - such as using basalt boulders for petroglyphs.