Pyroclastie density currents and eruption column at Lascar volcano, Chile, on 19 April 1993. The main current extends 5 km from the vent, having advanced at approximately 55 m S^-1. The plume ascended to 23 km. Jacques Et Aicha Guarinos Photos on back cover (top to bottom): (1) Ignimbrite plateau of the Bandelier Tuff, erupted from Valles caldera, Jemez Mountains, New Mexico, U.S.A. The caldera lies behind the hills in the distance. (2) Cross-bedded proximal 1980 ignimbrite of Mount St Helens, Washington, U.S.A. (3) Sampling ignimbrite for fabric studies: Peach Springs Tuff, California, U.S.A. (4) Pumice overpassing at the lower flow-boundary zone of a granular fluid-based pyroclastie density current. (5) Hot, one-day old deposit-derived ignimbrite lies in a canyon eroded into the 1991 ignimbrite of Mount Pinatubo, Philippines.