Report on Masaya (Nicaragua) — January 1982
Scientific Event Alert Network Bulletin, vol. 7, no. 1 (January 1982)
Managing Editor: Lindsay McClelland.
Masaya (Nicaragua) Small explosion heard followed by ashfall several kilometers south
Please cite this report as:
Global Volcanism Program, 1982. Report on Masaya (Nicaragua). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 7:1. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198201-344100.
11.984°N, 86.161°W; summit elev. 635 m
All times are local (unless otherwise noted)
"A small eruption occurred from the hole in Santiago Crater lava lake in the early evening of 16 December. No one witnessed the event, but people living S of the caldera reported hearing an explosion that was followed by ashfall several kilometers to the S. Highly vesiculated scoria fragments up to 20 cm in diameter fell as much as 200 m S of Santiago pit crater. As of late January, no subsequent explosive activity had been observed. A very large plume was still being continuously emitted. Incandescence was not readily visible during the day but was evident at night."
Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The twin volcanoes of Nindirí and Masaya, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals cause health hazards and crop damage.
Information Contacts: R. Stoiber, S. Williams, Dartmouth College; D. Fajardo B., Instituto de Investigaciones Sísmicas.