Tephra

Fragmental material produced by a volcanic eruption regardless of composition, fragment size or emplacement mechanism:

Tephra

Tephra fragments are classified by size:

1. Volcanic bombs (or volcanic blocks) - larger than 2.5 inches in diameter
2. Volcanic cinders - between 0.08 and 2.5 inches in diameter
3. Volcanic ash - particles smaller than 0.08 inches in diameter