Global Volcanism Program | Image GVP-04259
Pyroclastic flows descend the flanks of Arenal on 7 July 1987. This was part of the long eruption that began in 1968. The largest pyroclastic flow in this photo taken from the volcano observatory (2.5 km SSW of the summit) is traveling down the SSE flank.
Photo by William Melson, 1987 (Smithsonian Institution)