Global Volcanism Program | Image GVP-04303
A dark plume containing ash and mud punches through the surface of the crater lake of Poás volcano in July 1977. Ash-laden plumes rose at 25-minute intervals from the crater lake. Phreatic explosions began in May 1977 and were continuing at the time of this July photograph.
Photo by S. Racchini, 1977 (Universidad Nacional Costa Rica, courtesy of Jorge Barquero).