Volcanic and volcaniclastic fragmental deposits can be identified and differentiated through examination of their sediment-body characteristics, the physical properties of their constituent particle mixtures, and any impacts to terrain caused by the processes that emplace them. These identification criteria are observable and measurable at different scales: landscape scale (kilometers to meters), outcrop scale (meters to millimeters), and particle scale (millimeters and smaller). Landscape-scale criteria (seen on the ground surface and in vertical sections) involve the location, geometry, internal architecture, and lithofacies associations of the sediment body as a whole. Outcrop-scale criteria include the size, size distribution, composition, spatial arrangement, and physical characteristics of the deposit’s easily visible coarser particles. Particle-scale criteria include the size, size distribution, composition, spatial arrangement, and physical characteristics of the deposit’s finer particles, which are typically evaluated in the laboratory. Terrain impacts mainly include erosional and depositional structures or patterns, physical damage to trees and other vegetation, and occasionally chemical damage to vegetation. This chapter illustrates and discusses the identification criteria used in this book for most types of relatively fresh volcanic and volcaniclastic deposits. Identification criteria for lithified, chemically altered, profoundly weathered, or unusual types of volcanic deposits are not covered.