We have gained considerable experience with volcaniclastic materials over the past 30 years, but the field has undergone considerable growth in the decade following the 1980 eruption of Mount St. Helens. This eruption resulted in an accelerated research in explosive volcanic products and spurred a renewed interest in volcaniclastic materials as they relate to plate tectonic boundaries and explosive volcanism in general. Since the early 1970s a loosely defined field called â∈œsedimentary tectonicsâ∈ has emerged. A large part of the field of sedimentation and tectonics includes studies of volcaniclastic sedimentation, largely because of the direct association of tectonism, volcanism and sedimentation. This book attempts to illuminate the field and to present its salient features to sedimentologists not generally versed in volcaniclastic particles, deposits or facies.