Report on Masaya (Nicaragua) — November 1982
Scientific Event Alert Network Bulletin, vol. 7, no. 11 (November 1982)
Managing Editor: Lindsay McClelland.
Masaya (Nicaragua) Gas emission continues; incandescence within the inner crater
Please cite this report as:
Global Volcanism Program, 1982. Report on Masaya (Nicaragua) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 7:11. Smithsonian Institution.
11.984°N, 86.161°W; summit elev. 635 m
All times are local (unless otherwise noted)
"The approximately 3-year gas emission crisis from Santiago Crater continued in late 1982. Total SO2 flux was apparently reduced from the very large levels reported before. Incandescence within the inner crater was dull red-orange, as compared to the brilliant orange observed in February, 1982. The 7 October, 1982 explosion threw out abundant, juvenile, highly vesiculated scoria, which was often flattened and oxidized against the ground surface. Numerous fragments of sublimate minerals torn from the lip of the inner crater were ejected with the juvenile scoria. No new explosions have thrown debris out of Santiago Crater but several gas bursts have been reported by Park guards."
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: S. Williams, R. Stoiber, Dartmouth College; G. Hodgson V., D. Fajardo B., INETER.